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Laser in situ keratomileusis for correction of myopia and astigmatism after penetrating keratoplasty
Laser In Situ Keratomileusis for Correction of Myopia and Astigmatism after Penetrating Keratoplasty Eric D. Donnenfeld, MD,1 Howard S. Kornstein, MD,1 Abha Amin, MD,2 Mark D. Speaker, MD,2 John A. Seedor, MD,2 Paul D. Sforza, MD,1 Lori M. Landrio, OD,1 Henry D. Perry, MD1,2 Purpose: To determine the safety and effectiveness of laser in situ keratomileusis (LASIK) for visual rehabilitation of residual myopia and astigmatism after penetrating keratoplasty. Design: Prospective, noncomparative case series. Participants: LASIK was performed on 23 eyes of 22 patients unable to wear glasses or contact lenses after penetrating keratoplasty due to anisometropia, high astigmatism, and/or contact lens-intolerance. Methods: All patients underwent LASIK for visual rehabilitation after penetrating keratoplasty. Uncorrected visual acuity and best spectacle-corrected visual acuity, degree of anisometropia, and corneal transplant integrity were recorded before surgery, as well as at 1 month, 3 months, 6 months, and 12 months after LASIK surgery. Results: The mean spherical equivalent before surgery was ⫺7.58 ⫾ 4.42 diopters (D), which was reduced to ⫺1.09 ⫾ 2.01 D, ⫺0.79 ⫾ 1.84 D, ⫺0.77 ⫾ 1.25 D, and ⫺1.57 ⫾ 1.20 D, respectively, at 1, 3, 6, and 12 months after LASIK. The mean cylinder before surgery was 3.64 ⫾ 1.72 D, which was reduced to 1.98 ⫾ 1.15 D, 1.64 ⫾ 1.14 D, 1.48 ⫾ 0.92 D, and 1.29 ⫾ 1.04 D, respectively, at 1, 3, 6, and 12 months after LASIK. Spherical equivalent anisometropia was reduced from a mean of 6.88 ⫾ 4.4 D to 1.42 ⫾ 1.05 D at the final examination. Best-corrected visual acuity remained the same or improved in 21 of 23 eyes and decreased by 1 and 3 lines in 2 patients. There were no surgical flap or corneal transplant complications. Conclusions: LASIK is a viable treatment alternative for myopia and astigmatism after penetrating keratoplasty in patients who are contact lens-intolerant. LASIK is more effective in treating myopia than astigmatism after penetrating keratoplasty. Ophthalmology 1999;106:1966 –1975 With improved microsurgical techniques, penetrating keratoplasty has become a more common and successful procedure, with more than 40,000 surgeries performed annually.1 Unfortunately, postoperative visual rehabilitation remains challenging. Most patients will not tolerate more than 3 diopters (D) of anisometropia, because of image size disparity, or astigmatism of greater than 1.5 to 3 D.2,3 Refractive unpredictability after penetrating keratoplasty is extremely common, with most series documenting mean cylinders of 4 to 5 D and significant anisometropia.4 –10 Refractive anisometropia and high postoperative astigmatism can compromise the patient’s return to normal binocOriginally received: November 8, 1998. Revision accepted: June 1, 1999.
Manuscript no. 98526.
1
Department of Ophthalmology, North Shore University Hospital, Manhasset, New York, and New York University Medical Center, New York, New York. 2
Department of Ophthalmology, New York Eye and Ear Infirmary, New York, and New York Medical College, New York, New York. Presented in part at the American Academy of Ophthalmology Annual Meeting, New Orleans, Louisiana, November 1998. Supported in part by a grant from the Lions Club International Foundation, Oakbrook, Illinois. Reprint requests to Eric D. Donnenfeld, MD, Lions Eye Bank for Long Island at North Shore University Hospital, 300 Community Drive, Manhasset, NY 11530.
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ular function. Anisometropia in the undercorrected eye may result in headache, photophobia, burning, tearing, diplopia, and blurred vision.2 Binder11 reported in a series of patients after corneal transplant and cataract extraction that only 21 of 43 eyes achieved refractive errors within 2 D of emmetropia. Davis et al12 evaluated patients having combined cataract extraction with penetrating keratoplasty. Only 75% of patients fell between ⫺4.00 and ⫹2.00 when emmetropia was the goal. Flowers et al5 evaluated intraocular lens power calculation in combined corneal transplant and cataract extraction and reported that only 39% of patients had a refractive error within 2 D of emmetropia. The range of ametropia was from ⫺9.75 to 12.88 D, with 65% of the patients having myopic errors. Many of these patients who cannot be rehabilitated with spectacle correction can be aided by contact lenses.13 Contact lenses are vital to the rehabilitation of the postkeratoplasty patient. Ten percent to 30% of patients who have penetrating keratoplasty wear contact lenses for visual rehabilitation. The incidence of contact lens wear after penetrating keratoplasty for keratoconus is 25% to 50%.13,14 Both soft and gas-permeable contact lenses are extremely effective and remain the primary technique of visual rehabilitation after penetrating keratoplasty for patients who cannot tolerate spectacles.13–15 Their use is successful in 80% to 90% of cases.13 For myopia with low degrees of
Donnenfeld et al 䡠 LASIK for Myopia and Astigmatism after Corneal Transplant astigmatism, soft contact lenses are highly effective. Fitting with a gas-permeable contact lens may be required for patients with greater levels of regular astigmatism and any level of irregular astigmatism. Contact lens wear is not successful in all patients requiring visual correction after penetrating keratoplasty. The topographic abnormalities created by the penetrating keratoplasty wound can limit contact lens wear. In addition, contact lens intolerance may be caused by ocular, occupational, and systemic factors. Patients with dry eyes, blepharitis, lid abnormalities, and corneal neovascularization may not tolerate contact lenses. Occupational concerns include exposure to environmental factors such as wind, water, smoke, and poor sanitary conditions. Patients with poor manual dexterity, tremors, arthritis, or decreased visual acuity may be unable to manipulate a contact lens. Finally, unmotivated patients and patients unwilling or unable to practice good contact lens hygiene will be contact lens failures. In these patients, surgical alternatives may be the only option. The surgical alternatives for correction of postkeratoplasty astigmatism include corneal relaxing incisions and wedge resections.16 –18 Kirkness et al19 reported a series of 201 corneal transplants for keratoconus and found that 36 (18%) of patients required refractive surgery for the correction of astigmatism. These procedures can significantly decrease corneal cylinder and are highly effective procedures. However, they have minimal effect on spherical equivalent. Radial keratotomy can decrease low-to-intermediate levels of myopia. In a large clinical trial, radial keratotomy has been shown to be effective but is associated with glare, significant inaccuracy, refractive instability, increased risk of traumatic ruptured globe, and progressive hyperopia.20 Most series document poor visual rehabilitation with radial keratotomy for postkeratoplasty myopia, and radial keratotomy is not considered effective in its treatment.21 Pseudophakic patients with significant anisometropia can consider an intraocular lens exchange or a piggyback intraocular lens. Unfortunately, these patients have already often undergone a significant number of intraocular procedures. This alternative requires an additional intraocular procedure, which increases the risk of endothelial decompensation and glaucoma and may incite a graft rejection.22 Excimer laser photorefractive keratectomy (PRK) has been successful in the treatment of myopia and astigmatism but has a high incidence of complications when performed after penetrating keratoplasty.23,24 Postpenetrating keratoplasty myopic PRK is associated with increased incidence of irregular astigmatism and corneal scarring. In a multicenter trial, Maloney et al25 reported a 29% rate of two lines or more visual acuity loss in patients treated with a PRK after prior ocular surgery. In addition, significant regression limits the effectiveness of PRK after keratoplasty.26 Laser in situ keratomileusis (LASIK) was first described by Pallikaris et al27 in 1990. This procedure involves the use of a microkeratome to create a corneal flap. A suction ring is first placed around the cornea. Suction is applied, fixates the globe, and elevates the intraocular pressure (IOP). The microkeratome is passed through the fixated cornea, creating a lamellar incision with a nasal hinge. The corneal flap
is displaced nasally, and the excimer laser photoablation is then applied directly to the corneal stromal bed. The flap is replaced and realigned and is then allowed to adhere for several minutes. LASIK offers several advantages over PRK in the treatment of myopia and astigmatism. These advantages include, but are not limited to, rapid visual rehabilitation, decreased stromal scarring, less irregular astigmatism, minimal regression, and the ability to treat a greater range of refractive disorders.27–31 The major disadvantage of LASIK is the risk of complications related to the creation of the lamellar flap. LASIK has become increasingly popular over the past several years in treating myopia, astigmatism, and, more recently, hyperopia. There have been several case reports of LASIK after penetrating keratoplasty.32,33 In all of these cases, the patients had previously undergone penetrating keratoplasty for keratoconus, and the LASIK procedure resulted in an excellent visual outcome with no significant postoperative complications. The purpose of this study is to evaluate the effectiveness of LASIK in a series of patients for the treatment of myopia and astigmatism after penetrating keratoplasty.
Patients and Methods The study is a nonmasked, noncontrolled prospective clinical trial of LASIK for visual rehabilitation of significant myopia or astigmatism or both after penetrating keratoplasty. All patients were myopic or astigmatic or both after penetrating keratoplasty, and all but one patient were at least 6 months post suture removal. Patients were all spectacle correction-intolerant and were all offered contact lens visual rehabilitation. Nine eyes of eight patients had attempted gas-permeable contact lens fitting and were unsuccessful. All contact lenses had been removed for a minimum of 3 months before the LASIK procedure. Preoperative evaluation included uncorrected visual acuity (UCVA) and spectacle-corrected visual acuity by manifest refraction. Phakic patients underwent cycloplegic refraction (cyclopentolate hydrochloride 1%). All patients had preoperative videokeratography (Tomey Topographic Modeling System, Computed Anatomy, Inc, New York, NY), pachymetry (Humphrey ultrasound pachometer model 855; Humphrey Instruments, San Leandro, CA), slit-lamp examination, applanation tonometry, and dilated funduscopic examination. Nine patients also had preoperative and 3-month postoperative specular microscopy (Konan Noncon Robo Specular Microscope, Konan, Japan). Before treatment, all patients received two drops of proparacaine hydrochloride 1% to the treatment eye followed by one drop of prophylactic antibiotic ofloxacin 0.3% (Allergan Pharmaceuticals, Irvine, CA) or ciprofloxacin hydrochloride 0.3% (Alcon, Fort Worth, TX). At the slit lamp, the 6-o’clock meridian was marked at the limbus with a gentian violet marker. The patient was then prepared in the laser suite with 10% Betadine solution (Purdue Frederick, Norwalk, CT) applied to the closed lid and lashes of the operative eye. The Betadine was wiped away with a sterile gauze pad, and the lashes of the operative eye were isolated with a sterile plastic drape. The lid was held open with a locking lid speculum. The temporal cornea was then marked with either a radial or circular marker stained with gentian violet. All surgery was performed in either of two locations by three surgeons (EDD, JAS, or MDS). At both locations, the microkera-
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Ophthalmology Volume 106, Number 10, October 1999 tome was an automated corneal shaper (Chiron Vision, Claremont, CA) used in conjunction with an Argon Fluoride 193-nm Excimer Laser (VISX Star; VISX, Inc, Santa Clara, CA). The automated corneal shaper suction ring was placed on the eye concentric to the pupil with an attempt to avoid the temporal wound of the penetrating keratoplasty. The suction pump was activated to a pressure of 24 mmHg, and the IOP was elevated to at least 65 mmHg, verified by digital pressure and an applanation lens. Several drops of balanced salt solution (Alcon, Fort Worth, TX) were placed on the temporal cornea before the placement of the automated corneal shaper microkeratome head in the track of the suction ring. In all cases, a 160-m spacer was used. Using a foot control, the automated corneal shaper head was advanced on the suction ring track until it struck the permanent stop, at which time the direction was reversed. The microkeratome head returned to the beginning of the track, and suction was discontinued. The microkeratome head and suction ring were then removed. The flap was elevated with a cyclodialysis spatula, and the integrity of the flap was verified visually. The cyclodialysis spatula was used to wipe the stromal bed to ensure symmetric hydration. Before surgery, the desired myopic and cylindrical parameters were entered into the laser computer. Target refraction was emmetropia in all patients but two. In these two patients, the target refraction was 1 D less myopia than the myopic refraction of the fellow eye, with a goal of complete resolution of cylinder. Surgical discretion, based on patient age, humidity, and temperature in the room, was used for the LASIK treatment parameters, with a range of 10% to 25% reduction of myopic treatment, and a 0% to 10% reduction of cylindrical treatment. All patients had the fellow eye patched and were instructed to follow the helium–neon beam to facilitate centration. All ablations were performed with a fluence of 160 mJ/cm2 and at a repetition rate of 6 Hz. All ablations used a 6-mm ablation zone for up to 6 D of myopia in the corneal plane. For patients with greater than 6 D of myopia in the corneal plane, the ablation zone was decreased to 5.5 mm after the initial 6 D of treatment with a 6-mm ablation zone. The ablation was completed and the flap was replaced using a cyclodialysis spatula. The interface was irrigated copiously with balanced salt solution (Alcon, Fort Worth, TX), and attention was paid to ensure good flap apposition and the absence of flap folds and interface debris. The periphery of the flap was then dried with a surgical sponge, and the flap was allowed to adhere for 5 minutes. Adequate apposition was again ensured, and one drop of antibiotic (ofloxacin 0.3% or ciprofloxacin 0.3%) and one drop of nonsteroidal anti-inflammatory drug ketorolac tromethamine 0.5% (Acular; Allergan Pharmaceuticals, Irvine, CA) or diclofenac sodium 0.1% (Voltaren; Ciba, Atlanta, GA) were placed in the operative eye. The lid speculum was removed, the patient was brought to a slit lamp, and the postoperative eye was observed 5 minutes after speculum removal to verify good flap position. The patient then received an additional drop each of antibiotic and nonsteroidal anti-inflammatory drug, followed by the placement of a hard plastic external shield. The patient was requested to wear the shield for 3 nights. The patient was instructed to use prednisolone acetate 1% (Pred Forte; Allergan Pharmaceuticals, Irvine, CA) and antibiotic (ofloxacin 0.3% or ciprofloxacin 0.3%) four times daily for 1 week followed by prednisolone acetate 1% alone once daily for 2 weeks. Routine postoperative examinations were scheduled at 1 day, 1 week, 1 month, 3 months, 6 months, and 1 year after surgery. The UCVA, spectacle-corrected visual acuity, and slit-lamp biomicroscopy were performed at the time of these examinations. Corneal topography was performed at the 1-month, 3-month, 6-month, and 1-year examinations. Nine patients had repeat specular microscopy performed 3 months after surgery.
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Results Twenty-three eyes of 22 patients (14 female, 8 male) underwent LASIK for visual rehabilitation after penetrating keratoplasty in a prospective, nonmasked clinical study. Mean age at the time of the LASIK surgery was 52.9 years (range, 27– 80 years). Mean time from penetrating keratoplasty to LASIK was 44.1 months (range, 8 –120 months), and mean time from suture removal of the penetrating keratoplasty to LASIK was 35.3 months (range, 3–108 months). All patients were spectacle correction-intolerant, and eight patients had attempted gas-permeable contact lens wear without success. The most common indication for the penetrating keratoplasty was keratoconus (13 eyes), followed by pseudophakic bullous keratopathy (5 eyes), Fuchs endothelial dystrophy with combined cataract extraction (3 eyes), herpes simplex keratitis (1 eye), and herpes zoster keratitis (1 eye). Fifteen eyes were phakic and 8 eyes were pseudophakic. There were no statistically significant differences in spherical or cylindrical correction among the three groups. Three patients had undergone corneal relaxing incisions for high cylinder after penetrating keratoplasty and antecedent to their LASIK surgery. The relaxing incisions were all performed more than 6 months before LASIK. The patients were followed for a mean of 7.6 months after LASIK (range, 1–14 months). All 23 patients were seen at 1-month follow-up, 22 patients at 3 months, 16 patients at 6 months, and 7 patients at 1 year. One patient was lost to follow-up after 1 month, and his data were included in the analysis. Patients were treated based on their refractive myopia and cylinder. Patients were treated with a range of 75% to 90% of their refractive sphere based on surgeon discretion. For the first eight cases, the patients were treated with between 75% and 82% of refractive sphere. When the surgeons recognized that these patients were being undercorrected, the patients were treated with between 84% and 90% of their preoperative sphere for subsequent cases. Patients were treated with 90% to 100% of their refractive cylinder to the maximum level of cylinder treatable with the VISX Star laser (Visx Inc, Santa Clara, CA) with current software limitations. In one case, the patient had 8.5 D of cylinder, and this patient was treated in a sequential manner, with 6 D being treated on the original treatment and 2.75 D treated with a subsequent enhancement. A total of two patients underwent enhancement: one patient was treated for residual cylinder and one patient was treated for myopic undercorrection. In both of these cases, the visual results after enhancement were used in the analysis of postoperative results.
Refractive Spherical Equivalent All patients were myopic in the operative eye, with a mean refractive spherical equivalent of ⫺7.58 ⫾ 4.42 D on cycloplegic or pseudophakic refraction. Patients were evaluated at 1 month, 3 months, 6 months, and 1 year after LASIK. Results are summarized in Figure 1. Twenty-three eyes had a mean sphere of ⫺1.09 D ⫾ 2.01 D at 1 month, 22 eyes had a mean sphere of ⫺0.79 D ⫾ 1.84 D at 3 months, 16 eyes had a mean sphere of ⫺0.77 D ⫾ 1.25 D at 6 months, and 7 eyes had a mean sphere of ⫺1.57 D ⫾ 1.20 D at 1 year. There was no statistical difference in the postoperative spherical equivalents at these four times (P ⫽ 0.632). At 3 months, two patients were greater than 1-D hyperopic, one patient was greater than 1-D hyperopic at 6 months, and none of the eight patients were hyperopic at the 1-year follow-up. Forty-three percent (10 of 23 eyes) were within 1 D of targeted sphere and 74% (17 of 23 eyes) were within 2 D of targeted sphere at 1-month follow-up. Fifty-nine percent (13 of 22 eyes) were
Donnenfeld et al 䡠 LASIK for Myopia and Astigmatism after Corneal Transplant
Figure 1. Mean deviation from intended spherical equivalent correction shown before surgery and at postoperative examinations. Numbers of patients examined at each visit are shown.
within 1 D of targeted sphere at 3 months after surgery, and 73% (16 of 22 eyes) were within 2 D of targeted sphere. At 6 months after surgery, 63% (10 of 16 eyes) were within 1 D of targeted sphere, and 88% (14 of 16 eyes) were within 2 D of targeted sphere. At 1 year, 43% (3 of 7 eyes) were within 1 D of targeted sphere, and 71% (5 of 7 eyes) were within 2 D of targeted sphere (Fig 2). In 2 of 22 patients, the targeted refraction was plano. In two patients, the goal of treatment was not plano due to myopia in the untreated eye and the desire to avoid anisometropia. In these two cases, the target refraction was 1 D of myopia less than the fellow eye. In these two patients, the spherical equivalent of the fellow eye was ⫺7.25 D and ⫺3.5 D. The last spherical equivalent of the treated eye in these two cases was ⫺6.75 D and ⫺2.8 D, respectively. In Figure 3, the spherical equivalent is based on the target refraction. In this figure, the target refraction is plano in 21 eyes and ⫺6.25 and ⫺2.5 in the 2 eyes that were purposely undercorrected.
Refractive Cylinder Mean refractive cylinder before surgery was 3.64 D ⫾ 1.72 D. Mean cylinder in 23 eyes is summarized in Figures 4 and 5. At 1-month follow-up, mean cylinder in 23 eyes was 1.98 D ⫾ 1.15 D. Mean cylinder at 3 months after surgery in 22 eyes was ⫺1.64
Figure 2. Percentage of patients within 1, 2, and 3 diopters of intended refractive spherical equivalent at given postoperative intervals. Emmetropia was the goal for all but two patients.
Figure 3. Scattergram of target vs. actual correction of spherical equivalent at final postoperative examination after laser in situ keratomileusis.
D ⫾ 1.14 D. Mean cylinder at 6 months after surgery was 1.48 D ⫾ 0.92 D in 16 eyes. At 1-year postoperative, mean cylinder was ⫺1.29 D ⫾ 1.04 D in seven eyes. There was no statistical difference between the postoperative cylinder results at the four time intervals (P ⫽ 0.543). At 3 months after surgery, 9 of 22 eyes had a refractive cylinder of less than 1 D, 18 of 22 eyes had a refractive cylinder of less than 2 D, and 20 of 22 eyes had a refractive cylinder of less than 3 D. At 6 months after surgery, 8 of 16 eyes had a refractive cylinder of less than 1 D, 12 of 16 eyes had a refractive cylinder of less than 2 D, and 16 of 16 eyes had a refractive cylinder of less than 3 D. At 1-year follow-up, four of seven patients had a refractive cylinder of less than 1 D, five of seven patients had a refractive cylinder of less than 2 D, and seven of seven eyes had a refractive cylinder of less than 3 D (Fig 6). Three patients had an increase in cylinder at their final examination compared to their preoperative cylinder. In no case was a decentered ablation based on corneal topography responsible for the increase in postoperative cylinder, and in all three of these cases, there was no progression of the cylinder during the postoperative course. These three patients had a preoperative mean cylinder of 1.83 D, which increased to a mean of 2.58 at the final examination after LASIK.
Visual Acuity Sixteen (70%) of 23 patients had best spectacle-corrected visual acuity (BSCVA) of 20/40 or greater before surgery. At 1 month
Figure 4. Mean cylinder shown before surgery and at postoperative examinations. Numbers of patients examined at each visit are shown.
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Figure 5. Scattergram of target vs. actual correction of cylinder at final postoperative examination after laser in situ keratomileusis.
after LASIK, 16 (70%) of 23 had a BSCVA of 20/40 or greater. At 3 months, 15 (68%) of 22 eyes had a BSCVA of 20/40 or greater. At 6 months, 13 (81%) of 16 eyes had a BSCVA of 20/40 or greater. At 1 year, four (57%) of seven eyes had a BSCVA of 20/40 or greater. No patient lost UCVA. The preoperative UCVA ranged from 20/200 to counting fingers. At the final examination recorded, 8 (36%) of 22 eyes had a UCVA of 20/40 or greater, and 15 (68%) of 22 eyes had a UCVA of 20/70 or greater. In 9 eyes, BSCVA remained unchanged at the last visit after LASIK, while 12 eyes showed an improvement in BSCVA and 2 eyes showed a loss of BSCVA. Figure 7 shows lines of BSCVA and UCVA lost or gained. Figure 8 shows the percentage of patients with BSCVA of 20/25 or better, 20/40 or better, and 20/70 or better before LASIK and at their last visit after LASIK.
Anisometropia Before surgery, the mean difference in spherical equivalent between the patients’ operative eye and the fellow eye was 6.88 D ⫾ 4.4 D. The corneal transplant eye was always the more myopic eye. At the final postoperative refraction, this difference was reduced to 1.42 D ⫾ 1.05 D, a decrease of 79% (Fig 9). Eleven (50%) of 22 eyes were within 1 D, 17 eyes (77%) were within 2 D, 20 eyes (91%) were within 3 D, and all operative eyes were within 3.5 D of the untreated fellow eye (Fig 10).
Figure 6. Percentage of patients within 1, 2, and 3 diopters of intended refractive cylinder at given postoperative intervals. Zero cylinder was the goal for all patients.
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Figure 7. Gain and loss of visual acuity (Snellen lines). BSCVA ⫽ best spectacle-corrected visual acuity; UCVA ⫽ uncorrected visual acuity.
Corneal Transplant Complications The mean preoperative endothelial cell count in 9 patients was 1357, and at 3 months after surgery, the endothelial cell count in the same 9 patients was 1329. The endothelial cell counts are listed in Table 1. Mean endothelial cell loss was 2.1%, which is not statistically significant (P ⫽ 0.449). There were no wound dehiscences or flap complications. Specifically, there was no epithelial ingrowth, flap striae, free-flaps, or flap melts. No patient experienced a graft rejection episode after the LASIK surgery, and no patient had a loss of graft clarity. Two patients lost one or more lines of best-corrected visual acuity. One patient lost one line of visual acuity due to formation of a nuclear sclerotic cataract. The other patient lost three lines of visual acuity secondary to an increase in irregular astigmatism, which could not be spectacle corrected. This patient can now achieve 20/25 visual acuity with a gas-permeable contact lens.
Discussion The goal of therapeutic LASIK for visual rehabilitation after penetrating keratoplasty is not necessarily the same as LASIK for the correction of myopia, astigmatism, or both.
Figure 8. Percentage of patients within given ranges of best spectaclecorrected visual acuity before surgery and at final examination after laser in situ keratomileusis.
Donnenfeld et al 䡠 LASIK for Myopia and Astigmatism after Corneal Transplant Table 1. Pre- and Postoperative Endothelial Cell Counts
Figure 9. Mean anisometropia at preoperative and final postoperative examinations after laser in situ keratomileusis.
The primary goal of LASIK after penetrating keratoplasty is resolution of sufficient myopia and astigmatism to allow spectacle correction of the residual refractive error. The UCVA remains a secondary goal with LASIK after penetrating keratoplasty, whereas UCVA is clearly the primary objective of cosmetic LASIK. For this reason, return to binocularity and optimized best-corrected visual acuity with spectacles is the true endpoint for success with LASIK after penetrating keratoplasty. In our series, 21 of 22 patients were able to function binocularly with spectacles (17 of 22) or without correction (4 of 22). A major concern in performing LASIK after penetrating keratoplasty is the risk of damage to the corneal transplant or the graft– host–wound interface or both. Wound dehiscence after penetrating keratoplasty is a well-described phenomenon and can occur years after penetrating keratoplasty. In LASIK, the IOP is elevated to more than 65 mmHg, and there is a very small but very real risk of wound dehiscence with the possibility of extrusion of the intraocular contents. We recommend LASIK after penetrating keratoplasty be performed by experienced LASIK surgeons who can minimize the suction time needed during surgery. In our series, we experienced no wound complications. Unfortunately,
Figure 10. Distribution of anisometropia at the final postoperative examination after laser in situ keratomileusis.
Patient
Preoperative Endothelial Cell Count
Postoperative Endothelial Cell Count
1 2 3 4 5 6 7 8 9 Mean Standard deviation % Change P
1120 2040 975 1070 870 1450 890 1700 2100 1357.2 485.4 ⫺2.1 0.449753
1100 2100 850 1050 870 1400 870 1650 2070 1328.9 504.1
irregular as well as regular astigmatism is a common finding after penetrating keratoplasty. A potential advantage of LASIK is that there is evidence that the flap in LASIK creates a more regular ocular surface than occurs in PRK.28 Although irregular astigmatism can be a significant problem after LASIK for visual rehabilitation following penetrating keratoplasty, we believe there is less irregular astigmatism compared to PRK (Figs 11 and 12). In our series, one patient lost visual acuity due to increased irregular astigmatism. A second potential advantage of LASIK over surface excimer laser photoablation is that there is better corneal sensation after LASIK than after PRK.34 In LASIK, the 2 to 3 clock-hours of hinge nasally allows the passage of corneal nerves into the central cornea. This has been shown to provide improved sensation. One of the main predictors of graft survivability is corneal sensation. There is always a diminution of corneal sensation after penetrating keratoplasty due to trephination of the corneal nerves. LASIK offers an additional advantage over PRK in that there is less loss of corneal sensation. In our series, 19 of 23 patients continued to be myopic after LASIK. In two eyes, this was done purposefully to prevent anisometropia with the fellow eye. Additionally, our nomogram was less aggressive with our first eight patients. In general, we were comfortable leaving our patients mildly myopic and allowing them to be visually rehabilitated with spectacles, particularly when they wore spectacles for the other eye. The most common indication in the United States for penetrating keratoplasty is pseudophakic bullous keratopathy.35–37 There is a high incidence of macular pathology after penetrating keratoplasty for pseudophakic bullous keratopathy. Patients whose final visual rehabilitation is limited by macular pathology often are less motivated to wear contact lenses. Chronic cystoid macular edema is seen in 42% to 50% of cases of pseudophakic bullous keratopathy,38,39 and there is a 6% to 24% incidence of involutional macular degeneration after penetrating keratoplasty,40,41 both of which can severely limit visual rehabilitation. These patients may have a best-corrected visual acuity ranging from 20/25 to counting fingers, with the majority having
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Ophthalmology Volume 106, Number 10, October 1999 visual acuities of 20/40 or less. Price et al14 reported that only 50% of patients with grafts for pseudophakic bullous keratopathy achieved a visual acuity of 20/40 or better, whereas Zaidman and Goldman42 reported 31% and Speaker et al43 reported a 22% incidence of visual acuity of 20/40 or better after penetrating keratoplasty for pseudophakic bullous keratopathy. Pseudophakic bullous keratopathy occurs overwhelmingly in an elderly population. Assuming these patients have good visual acuity in their fellow eye, there may be little motivation for an elderly individual, with no possibility of visual rehabilitation to the level of the fellow eye, to wear a soft or gas-permeable contact lens. These patients have had previous cataract surgery, penetrating keratoplasty, approximately 1 year of postoperative visits before suture removal, and, often, a vitreoretinal consultation. When they are ready for their visual rehabilitation, patients are told they cannot be improved with spectacles because of significant anisometropia. Even though their central visual acuity may be diminished, these patients would benefit greatly from the expanded peripheral visual field. These patients are excellent candidates for postpenetrating keratoplasty LASIK, which can offer permanent rehabilitation of their refractive error. There are several alterations of our normal LASIK technique when treating myopia or astigmatism or both after penetrating keratoplasty. An accurate assessment of the patient’s true refraction depends on the donor cornea returning to its normal shape after suture removal. With gaspermeable contact lens wear, most LASIK surgeons recommend a minimum of 1 month to allow resolution of corneal warpage, and with long-term gas-permeable contact lens wear, the corneal warpage may take several months to abate. We chose to wait a minimum of 6 months after suture removal before LASIK in all but one patient. In our series, the mean time from penetrating keratoplasty to LASIK was 44 months, and the mean time from suture removal was 34 months. We recommend this prolonged period to allow the corneal wound to equilibrate completely. More important, we are concerned with the ability of the corneal transplant
wound to withstand the elevated IOP of the suction head. In LASIK, IOP is elevated to at least 65 mmHg to draw the cornea into the circular opening and firmly hold it in place while the microkeratome creates a surgical flap. Inadequate pressure will predispose to flap complications, such as free flaps, thin flaps, and buttonholes. A corneal transplant wound is never as secure as a normal cornea, but we suggest that allowing 6 months after suture removal will provide additional time for wound healing to occur. In our series, there were no complications related to the increased IOP of LASIK and, specifically, no wound dehiscences. The surgical LASIK procedure we used was our standard technique, altered only to avoid initiating the incision at the corneal transplant graft– host interface. The patients’ donor corneas ranged in size from 7.75 to 8.5 mm in diameter. The flap diameter created by the automated corneal shaper is approximately 8.5 mm. Therefore, the flap is almost exactly the same size as the donor cornea. We avoided initiating the flap temporally at the graft– host interface while attempting to center the flap over the pupil. We also tried to begin the incision 1 mm temporal or 1 mm nasal to the temporal aspect of the graft– host interface based on centration of the corneal transplant over the pupil. Doing this allowed the flap to drape over the wound. We believe this creates better wound apposition of the flap to the recipient bed. The corneal scar tissue at the penetrating keratoplasty wound tends to be less pliable than normal corneal tissue. In addition, initiating the LASIK incision temporally prevents applying additional pressure directly to the corneal transplant wound and may decrease the risk of wound dehiscence. After repositioning the corneal flap, we generally wait 2 minutes for the flap to adhere to the underlying stromal bed. This is altered in LASIK after penetrating keratoplasty, where we wait 5 minutes for flap adherence before removing the speculum. We are also more liberal with our use of postoperative corticosteroids than in our normal LASIK patients. We use fluorometholone 0.1% four times daily for 5 days after conventional LASIK surgery. In LASIK after penetrating keratoplasty, we used prednisolone acetate 1% four times daily for 1 week and then pred-
Figure 11. Corneal topography of a patient before undergoing laser in situ keratomileusis.
Figure 12. Post laser in situ keratomileusis corneal topography for same patient shown in Figure 11.
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Donnenfeld et al 䡠 LASIK for Myopia and Astigmatism after Corneal Transplant nisolone acetate 1% once daily for 2 weeks. We believe the additional use of corticosteroids is indicated because of the potential risk of graft rejection after any surgical procedure on a penetrating keratoplasty. In our series, we experienced no episodes of graft rejection. After penetrating keratoplasty, many patients will have irregular astigmatism, which, although not amenable to spectacle correction, can be rehabilitated with a gas-permeable contact lens. We discourage these patients if they are at all contact lens-tolerant from having LASIK performed, as the Excimer Laser (VISX, Inc) currently is not successful in treating irregular astigmatism. The VISX Star Laser creates a 6-mm-ablation zone for up to 6 D of myopia in the corneal plane, decreasing to 5 mm with a single-pass multizone technology. Although this technology is excellent for regular astigmatism and myopia, it cannot currently treat irregular astigmatism. We anticipate that the development of flying spot Excimer Lasers guided by corneal topography will successfully treat some forms of irregular astigmatism in the next several years. This will allow even more accurate treatment of postpenetrating keratoplasty refractive errors. Although we only treated myopia and myopic astigmatism, LASIK also may be effective in the treatment of hyperopia and hyperopic astigmatism, although their larger peripheral ablations may impact directly on the corneal transplant wound. In conclusion, LASIK is successful in treating postkeratoplasty myopia and astigmatism in most patients. Patients were overwhelmingly able to resolve their anisometropia and achieve binocular function. LASIK was more effective in treating residual myopia than astigmatism. We advocate a conservative approach to treating refractive errors after penetrating keratoplasty with LASIK. Contact lenses remain the standard of care and are to be encouraged whenever feasible. When contact lens use is not possible, we suggest slightly undercorrecting the myopia, especially when the fellow eye is myopic. Return to binocularity is the primary goal of treatment. In addition, LASIK offers the advantage of allowing enhancements at a later date for residual refractive errors. LASIK offers the corneal surgeon an additional tool in the visual rehabilitation of the corneal transplant patient.
References 1. Statistical Report, Eye Bank Association of America, 101 Connecticut Avenue, N.W., Suite 601, Washington, DC 20306, 1993. 2. Brooks SE, Johnson D, Fischer N. Anisometropia and binocularity. Ophthalmology 1996;103:1139 – 43. 3. Rubin ML. Anisometropia. In: Fraunfelder FT, Hampton Roy F, eds; Grove J, assoc. ed. Current Ocular Therapy 4. Philadelphia: Saunders, 1995;757– 8. 4. Perl T, Charlton KH, Binder PS. Disparate diameter grafting. Astigmatism, intraocular pressure, and visual acuity. Ophthalmology 1981;88:774 – 81. 5. Flowers CW, McCleod SD, McDonnell PJ, et al. Evaluation of intraocular lens power calculation formulas in the triple procedure. J Cataract Refract Surg 1996;22:116 –22.
6. Perlman EM. An analysis and interpretation of refractive errors after penetrating keratoplasty. Ophthalmology 1981;88: 39 – 45. 7. Clinch TE, Thompson HW, Gardner BP, et al. An adjustable double running suture technique for keratoplasty. Am J Ophthalmol 1993;116:201– 6. 8. Binder PS. The effect of suture removal on postkeratoplasty astigmatism. Am J Ophthalmol 1988;105:637– 45. 9. Samples JR, Binder PS. Visual acuity, refractive error, and astigmatism following corneal transplantation for pseudophakic bullous keratopathy. Ophthalmology 1985;92:1554 – 60. 10. Assil KK, Zarnegar SR, Schanzlin DJ. Visual outcome after penetrating keratoplasty with double continuous or combined interrupted and continuous suture wound closure. Am J Ophthalmol 1992;114:63–71. 11. Binder PS. Intraocular lens powers used in the triple procedure. Effect on visual acuity and refractive error. Ophthalmology 1985;92:1561– 6. 12. Davis EA, Azar DT, Jakobs FM, Stark WJ. Refractive and keratometric results after the triple procedure. Experience with early and late suture removal. Ophthalmology 1998;105:624 – 30. 13. Lopatynsky MO, Cohen EJ. Post-keratoplasty fitting for visual rehabilitation. In: Kastl PR, ed. Contact Lenses: The CLAO Guide to Basic Science and Clinical Practice. Dubuque, Iowa: Kendall/Hunt Pub. Co., 1995;79 –90. 14. Price FW Jr, Whitson WE, Marks RG. Progression of visual acuity after penetrating keratoplasty. Ophthalmology 1991;98: 1177– 85. 15. Speaker MG, Cohen EJ, Edelhauser HF, et al. Effect of gas-permeable contact lenses on the endothelium of corneal transplants. Arch Ophthalmol 1991;109:1703– 6. 16. Troutman RC. Corneal wedge resections and relaxing incisions for postkeratoplasty astigmatism. Int Ophthalmol Clin 1983;23:161– 8. 17. Lugo M, Donnenfeld ED, Arentsen JJ. Corneal wedge resection for high astigmatism following penetrating keratoplasty. Ophthalmic Surg 1987;18:650 –3. 18. Maguire LJ, Bourne WM. Corneal topography of transverse keratotomies for astigmatism after penetrating keratoplasty. Am J Ophthalmol 1989;107:323–30. 19. Kirkness CM, Ficker LA, Steele AD, Rice NS. Refractive surgery for graft-induced astigmatism after penetrating keratoplasty for keratoconus. Ophthalmology 1991;98:1786 –92. 20. Waring GO III, Lynn MJ, Gelender H, et al. Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study one year after surgery. Ophthalmology 1985;92:177–98, 307. 21. Gothard TW, Agapitos PJ, Bowers RA, et al. Four-incision radial keratotomy for high myopia after penetrating keratoplasty. Refract Corneal Surg 1993;9:51–7. 22. Ficker LA, Kirkness CM, Steele AD. Intraocular surgery following penetrating keratoplasty: the risks and advantages. Eye 1990;4:693–7. 23. Campos M, Hertzog L, Garbus J, et al. Photorefractive keratectomy for severe post-keratoplasty astigmatism. Am J Ophthalmol 1992;114:429 –36. 24. Amm M, Duncker GI, Schroder E. Excimer laser correction of high astigmatism after keratoplasty. J Cataract Refract Surg 1996;22:313–7. 25. Maloney RK, Chan WK, Steinert R, et al. A multicenter trial of photorefractive keratectomy for residual myopia after previous ocular surgery. Summit Therapeutic Refractive Study Group. Ophthalmology 1995;102:1042–52; discussion, 1052–3.
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Ophthalmology Volume 106, Number 10, October 1999 26. Lazzaro DR, Haight DH, Belmont SC, et al. Excimer laser keratectomy for astigmatism occurring after penetrating keratoplasty. Ophthalmology 1996;103:458 – 64. 27. Pallikaris IG, Papatzanaki ME, Stathi EZ, et al. Laser in situ keratomileusis. Lasers Surg Med 1990;10:463– 8. 28. Hersh PS, Brint SF, Maloney RK, et al. Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia. A randomized prospective study. Ophthalmology 1998;105:1512–22; discussion, 1522–3. 29. Helmy SA, Salah A, Badawy TT, Sidky AN. Photorefractive keratectomy and laser in situ keratomileusis for myopia between 6.00 and 10.00 diopters. J Refract Surg 1996;12:417– 21. 30. Salah T, Waring GO III, el-Maghraby A, et al. Excimer laser in-situ keratomileusis (LASIK) under a corneal flap for myopia of 2 to 20 D. Trans Am Ophthalmol Soc 1995;93:163– 83; discussion, 184 –90. 31. Azar DT, Farah SG. Laser in situ keratomileusis versus photorefractive keratectomy. An update on indications and safety. Ophthalmology 1998;105:1357– 8. 32. Arenas E, Maglione A. Laser in situ keratomileusis for astigmatism and myopia after penetrating keratoplasty. J Refract Surg 1997;13:27–32. 33. Zaldivar R, Davidorf J, Oscherow S. LASIK for myopia and astigmatism after penetrating keratoplasty. J Refract Surg 1997;13:501–2. 34. Kanellopoulos AJ, Pallikaris IG, Donnenfeld ED, et al. Comparison of corneal sensation following photorefractive keratectomy and laser in situ keratomileusis. J Cataract Refract Surg 1997;23:34 – 8.
35. Corneal Transplant Recipient Diagnosis Report. 1993; 1993 Statistical Report. Eye Bank Association of America, 1001 Connecticut Avenue, N.W., Suite 601, Washington, DC 20030. 36. Brady SE, Rapuano CJ, Arentsen JJ, et al. Clinical indications for and procedures associated with penetrating keratoplasty, 1983–1988. Am J Ophthalmol 1989;108:118 –22. 37. Mamalis N, Anderson CW, Kreisler KR, et al. Changing trends in the indications for penetrating keratoplasty. Arch Ophthalmol 1992;110:1409 –11. 38. Heidemann DG, Dunn SP. Transsclerally sutured intraocular lenses in penetrating keratoplasty. Am J Ophthalmol 1992; 113:619 –25. 39. Kornmehl EW, Steinert RF, Odrich MG, Stevens JB. Penetrating keratoplasty for pseudophakic bullous keratopathy associated with closed-loop anterior chamber intraocular lenses. Ophthalmology 1990;97:407–12; discussion, 413– 4. 40. Holland EJ, Daya SM, Evangelista A, et al. Penetrating keratoplasty and transscleral fixation of posterior chamber lens. Am J Ophthalmol 1992;114:182–7. 41. Gaster RN, Ong HV. Results of penetrating keratoplasty with posterior chamber intraocular lens implantation in the absence of a lens capsule. Cornea 1991;10:498 –506. 42. Zaidman GW, Goldman S. A prospective study on the implantation of anterior chamber intraocular lenses during keratoplasty for pseudophakic and aphakic bullous keratopathy. Ophthalmology 1990;97:757– 62. 43. Speaker MG, Lugo M, Laibson PR, et al. Penetrating keratoplasty for pseudophakic bullous keratopathy. Management of the intraocular lens. Ophthalmology 1988;95:1260 – 8.
Discussion by Jonathan H. Talamo, MD Donnenfeld and colleagues report data from the first sizable series of laser in situ keratomileusis (LASIK) treatments after penetrating keratoplasty (PK). In doing so, the authors provide preliminary evidence that LASIK is an effective tool to reduce post-PK ametropia, particularly if the clinical endpoint is improved spectacle tolerance rather than excellent uncorrected visual acuity. However, before discussing the promising implications of these results, it is important to remind the reader of the limitations of this type of clinical study. As with many case series, it is not prospective, nonrandomized, and has a small sample size. Because follow-up is limited (the majority of eyes were examined for only 3 months after surgery), the refractive stability of the procedure and the subsequent health of the corneal graft in this setting have not been unequivocally established. Additional shortcomings of this case series include the very wide range of refractive errors studied and the variation in best spectacle-corrected visual acuity (BSCVA) recorded before surgery. Thirty percent of eyes had BSCVA of 20/40 or worse before LASIK, and as such, it may have been difficult to obtain an accurate preoperative manifest refraction. Although such findings are not unexpected in eyes that have undergone corneal transplantation, it is difficult to draw conclusions about exactly when and how LASIK is most effective in this setting.
From Cornea Consultants, Boston, and the Laser Eye Center of Boston, Boston, Massachusetts. Address correspondence to Jonathan H. Talamo, MD, Cornea Consultants, 100 Charles River Plaza, Boston, MA 02114. E-mail: [email protected].
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Table 1. Surgery for Ametropia after PK BSCVA Loss ⱖ 2 Lines Author Lazzaro Amm Campos Donnenfeld Hersh
Procedure
Percent
Reference
PRK/PARK
0–38
Ophtha 1996 JCRS 1996 AJO 1992
LASIK PRK/PARK LASIK
4.3 12 3
Ophth 1998
Previous reports have established that photorefractive keratectomy (PRK) and photoastigmatic refractive keratectomy (PARK) can significantly reduce residual ametropia after PK.1–3 However, the safety, efficacy, and predictability of surface ablation decrease when used for the high degrees of refractive correction necessary,4 which may render PRK/PARK much less useful in this setting. As the authors demonstrate, the incidence of BSCVA loss of two or more Snellen lines generally is much higher after PRK than for LASIK, regardless of whether the procedure is performed after PK or for naturally occurring refractive error (Table 1). In addition to BSCVA loss, other safety issues raised by the authors include the risk of wound rupture and graft rejection. The possibility of suction-related retinal vascular or optic nerve compromise should also be considered, particularly if the patient is older or has a history of such conditions. The treatment of surgically induced astigmatism after PK remains a major challenge, and the results presented in this article do not represent a significant improvement in this area. Table 2
Donnenfeld et al 䡠 LASIK for Myopia and Astigmatism after Corneal Transplant Table 2. Surgery for Ametropia after PK Astigmatism Reduction Author Lazzaro Amm Campos Donnenfeld Kirkness
Procedure PRK/PARK LASIK AK/CS
Percent 38–57 55 46
Eyes (n) 7 16 12 22 (3 mo) 42
provides a summary of mean postkeratoplasty astigmatism after incisional5 and photorefractive procedures1–3 as reported in representative studies in the peer-reviewed literature. I agree with the authors that difficulties in accurately measuring refractive cylinder due to irregular astigmatism and decreased BSCVA as well as the long-term instability of PK wounds continue to be major obstacles to improved results. Hopefully, the ability to perform larger diameter lamellar keratectomy resections and custom ablations with flying spot lasers will yield progress. It seems reasonable to conclude that in carefully selected patients with well-healed corneal transplant wounds and minimal irregular astigmatism, LASIK performed by an experienced sur-
geon will safely and effectively reduce ametropia after PK for the purpose of improved spectacle tolerance. A much larger cohort of patients will be necessary to establish the true incidence of flap and graft-related complications. References 1. Campos M, Hertzog L, Garbus J, et al. Photorefractive keratectomy for severe postkeratoplasty astigmatism. Am J Ophthalmol 1992;114:429 –36. 2. Lazzaro DR, Haight DH, Belmont SC, et al. Excimer laser keratectomy for astigmatism occurring after penetrating keratoplasty. Ophthalmology 1996;103:458 – 64. 3. Amm M, Duncker GI, Schroder E. Excimer laser correction of high astigmatism after keratoplasty. J Cataract Refract Surg 1996;22:313–7. 4. Hersh PS, Brint SF, Maloney RK, et al. Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia. A randomized prospective study. Ophthalmology 1998;105:1512–22; discussion, 1522–3. 5. Kirkness CM, Ficker LA, Steele AD, Rice NS. Refractive surgery for graft-induced astigmatism after penetrating keratoplasty for keratoconus. Ophthalmology 1991;98:1786 –92.
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Manuscript no. 98526.
1
Department of Ophthalmology, North Shore University Hospital, Manhasset, New York, and New York University Medical Center, New York, New York. 2
Department of Ophthalmology, New York Eye and Ear Infirmary, New York, and New York Medical College, New York, New York. Presented in part at the American Academy of Ophthalmology Annual Meeting, New Orleans, Louisiana, November 1998. Supported in part by a grant from the Lions Club International Foundation, Oakbrook, Illinois. Reprint requests to Eric D. Donnenfeld, MD, Lions Eye Bank for Long Island at North Shore University Hospital, 300 Community Drive, Manhasset, NY 11530.
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ular function. Anisometropia in the undercorrected eye may result in headache, photophobia, burning, tearing, diplopia, and blurred vision.2 Binder11 reported in a series of patients after corneal transplant and cataract extraction that only 21 of 43 eyes achieved refractive errors within 2 D of emmetropia. Davis et al12 evaluated patients having combined cataract extraction with penetrating keratoplasty. Only 75% of patients fell between ⫺4.00 and ⫹2.00 when emmetropia was the goal. Flowers et al5 evaluated intraocular lens power calculation in combined corneal transplant and cataract extraction and reported that only 39% of patients had a refractive error within 2 D of emmetropia. The range of ametropia was from ⫺9.75 to 12.88 D, with 65% of the patients having myopic errors. Many of these patients who cannot be rehabilitated with spectacle correction can be aided by contact lenses.13 Contact lenses are vital to the rehabilitation of the postkeratoplasty patient. Ten percent to 30% of patients who have penetrating keratoplasty wear contact lenses for visual rehabilitation. The incidence of contact lens wear after penetrating keratoplasty for keratoconus is 25% to 50%.13,14 Both soft and gas-permeable contact lenses are extremely effective and remain the primary technique of visual rehabilitation after penetrating keratoplasty for patients who cannot tolerate spectacles.13–15 Their use is successful in 80% to 90% of cases.13 For myopia with low degrees of
Donnenfeld et al 䡠 LASIK for Myopia and Astigmatism after Corneal Transplant astigmatism, soft contact lenses are highly effective. Fitting with a gas-permeable contact lens may be required for patients with greater levels of regular astigmatism and any level of irregular astigmatism. Contact lens wear is not successful in all patients requiring visual correction after penetrating keratoplasty. The topographic abnormalities created by the penetrating keratoplasty wound can limit contact lens wear. In addition, contact lens intolerance may be caused by ocular, occupational, and systemic factors. Patients with dry eyes, blepharitis, lid abnormalities, and corneal neovascularization may not tolerate contact lenses. Occupational concerns include exposure to environmental factors such as wind, water, smoke, and poor sanitary conditions. Patients with poor manual dexterity, tremors, arthritis, or decreased visual acuity may be unable to manipulate a contact lens. Finally, unmotivated patients and patients unwilling or unable to practice good contact lens hygiene will be contact lens failures. In these patients, surgical alternatives may be the only option. The surgical alternatives for correction of postkeratoplasty astigmatism include corneal relaxing incisions and wedge resections.16 –18 Kirkness et al19 reported a series of 201 corneal transplants for keratoconus and found that 36 (18%) of patients required refractive surgery for the correction of astigmatism. These procedures can significantly decrease corneal cylinder and are highly effective procedures. However, they have minimal effect on spherical equivalent. Radial keratotomy can decrease low-to-intermediate levels of myopia. In a large clinical trial, radial keratotomy has been shown to be effective but is associated with glare, significant inaccuracy, refractive instability, increased risk of traumatic ruptured globe, and progressive hyperopia.20 Most series document poor visual rehabilitation with radial keratotomy for postkeratoplasty myopia, and radial keratotomy is not considered effective in its treatment.21 Pseudophakic patients with significant anisometropia can consider an intraocular lens exchange or a piggyback intraocular lens. Unfortunately, these patients have already often undergone a significant number of intraocular procedures. This alternative requires an additional intraocular procedure, which increases the risk of endothelial decompensation and glaucoma and may incite a graft rejection.22 Excimer laser photorefractive keratectomy (PRK) has been successful in the treatment of myopia and astigmatism but has a high incidence of complications when performed after penetrating keratoplasty.23,24 Postpenetrating keratoplasty myopic PRK is associated with increased incidence of irregular astigmatism and corneal scarring. In a multicenter trial, Maloney et al25 reported a 29% rate of two lines or more visual acuity loss in patients treated with a PRK after prior ocular surgery. In addition, significant regression limits the effectiveness of PRK after keratoplasty.26 Laser in situ keratomileusis (LASIK) was first described by Pallikaris et al27 in 1990. This procedure involves the use of a microkeratome to create a corneal flap. A suction ring is first placed around the cornea. Suction is applied, fixates the globe, and elevates the intraocular pressure (IOP). The microkeratome is passed through the fixated cornea, creating a lamellar incision with a nasal hinge. The corneal flap
is displaced nasally, and the excimer laser photoablation is then applied directly to the corneal stromal bed. The flap is replaced and realigned and is then allowed to adhere for several minutes. LASIK offers several advantages over PRK in the treatment of myopia and astigmatism. These advantages include, but are not limited to, rapid visual rehabilitation, decreased stromal scarring, less irregular astigmatism, minimal regression, and the ability to treat a greater range of refractive disorders.27–31 The major disadvantage of LASIK is the risk of complications related to the creation of the lamellar flap. LASIK has become increasingly popular over the past several years in treating myopia, astigmatism, and, more recently, hyperopia. There have been several case reports of LASIK after penetrating keratoplasty.32,33 In all of these cases, the patients had previously undergone penetrating keratoplasty for keratoconus, and the LASIK procedure resulted in an excellent visual outcome with no significant postoperative complications. The purpose of this study is to evaluate the effectiveness of LASIK in a series of patients for the treatment of myopia and astigmatism after penetrating keratoplasty.
Patients and Methods The study is a nonmasked, noncontrolled prospective clinical trial of LASIK for visual rehabilitation of significant myopia or astigmatism or both after penetrating keratoplasty. All patients were myopic or astigmatic or both after penetrating keratoplasty, and all but one patient were at least 6 months post suture removal. Patients were all spectacle correction-intolerant and were all offered contact lens visual rehabilitation. Nine eyes of eight patients had attempted gas-permeable contact lens fitting and were unsuccessful. All contact lenses had been removed for a minimum of 3 months before the LASIK procedure. Preoperative evaluation included uncorrected visual acuity (UCVA) and spectacle-corrected visual acuity by manifest refraction. Phakic patients underwent cycloplegic refraction (cyclopentolate hydrochloride 1%). All patients had preoperative videokeratography (Tomey Topographic Modeling System, Computed Anatomy, Inc, New York, NY), pachymetry (Humphrey ultrasound pachometer model 855; Humphrey Instruments, San Leandro, CA), slit-lamp examination, applanation tonometry, and dilated funduscopic examination. Nine patients also had preoperative and 3-month postoperative specular microscopy (Konan Noncon Robo Specular Microscope, Konan, Japan). Before treatment, all patients received two drops of proparacaine hydrochloride 1% to the treatment eye followed by one drop of prophylactic antibiotic ofloxacin 0.3% (Allergan Pharmaceuticals, Irvine, CA) or ciprofloxacin hydrochloride 0.3% (Alcon, Fort Worth, TX). At the slit lamp, the 6-o’clock meridian was marked at the limbus with a gentian violet marker. The patient was then prepared in the laser suite with 10% Betadine solution (Purdue Frederick, Norwalk, CT) applied to the closed lid and lashes of the operative eye. The Betadine was wiped away with a sterile gauze pad, and the lashes of the operative eye were isolated with a sterile plastic drape. The lid was held open with a locking lid speculum. The temporal cornea was then marked with either a radial or circular marker stained with gentian violet. All surgery was performed in either of two locations by three surgeons (EDD, JAS, or MDS). At both locations, the microkera-
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Ophthalmology Volume 106, Number 10, October 1999 tome was an automated corneal shaper (Chiron Vision, Claremont, CA) used in conjunction with an Argon Fluoride 193-nm Excimer Laser (VISX Star; VISX, Inc, Santa Clara, CA). The automated corneal shaper suction ring was placed on the eye concentric to the pupil with an attempt to avoid the temporal wound of the penetrating keratoplasty. The suction pump was activated to a pressure of 24 mmHg, and the IOP was elevated to at least 65 mmHg, verified by digital pressure and an applanation lens. Several drops of balanced salt solution (Alcon, Fort Worth, TX) were placed on the temporal cornea before the placement of the automated corneal shaper microkeratome head in the track of the suction ring. In all cases, a 160-m spacer was used. Using a foot control, the automated corneal shaper head was advanced on the suction ring track until it struck the permanent stop, at which time the direction was reversed. The microkeratome head returned to the beginning of the track, and suction was discontinued. The microkeratome head and suction ring were then removed. The flap was elevated with a cyclodialysis spatula, and the integrity of the flap was verified visually. The cyclodialysis spatula was used to wipe the stromal bed to ensure symmetric hydration. Before surgery, the desired myopic and cylindrical parameters were entered into the laser computer. Target refraction was emmetropia in all patients but two. In these two patients, the target refraction was 1 D less myopia than the myopic refraction of the fellow eye, with a goal of complete resolution of cylinder. Surgical discretion, based on patient age, humidity, and temperature in the room, was used for the LASIK treatment parameters, with a range of 10% to 25% reduction of myopic treatment, and a 0% to 10% reduction of cylindrical treatment. All patients had the fellow eye patched and were instructed to follow the helium–neon beam to facilitate centration. All ablations were performed with a fluence of 160 mJ/cm2 and at a repetition rate of 6 Hz. All ablations used a 6-mm ablation zone for up to 6 D of myopia in the corneal plane. For patients with greater than 6 D of myopia in the corneal plane, the ablation zone was decreased to 5.5 mm after the initial 6 D of treatment with a 6-mm ablation zone. The ablation was completed and the flap was replaced using a cyclodialysis spatula. The interface was irrigated copiously with balanced salt solution (Alcon, Fort Worth, TX), and attention was paid to ensure good flap apposition and the absence of flap folds and interface debris. The periphery of the flap was then dried with a surgical sponge, and the flap was allowed to adhere for 5 minutes. Adequate apposition was again ensured, and one drop of antibiotic (ofloxacin 0.3% or ciprofloxacin 0.3%) and one drop of nonsteroidal anti-inflammatory drug ketorolac tromethamine 0.5% (Acular; Allergan Pharmaceuticals, Irvine, CA) or diclofenac sodium 0.1% (Voltaren; Ciba, Atlanta, GA) were placed in the operative eye. The lid speculum was removed, the patient was brought to a slit lamp, and the postoperative eye was observed 5 minutes after speculum removal to verify good flap position. The patient then received an additional drop each of antibiotic and nonsteroidal anti-inflammatory drug, followed by the placement of a hard plastic external shield. The patient was requested to wear the shield for 3 nights. The patient was instructed to use prednisolone acetate 1% (Pred Forte; Allergan Pharmaceuticals, Irvine, CA) and antibiotic (ofloxacin 0.3% or ciprofloxacin 0.3%) four times daily for 1 week followed by prednisolone acetate 1% alone once daily for 2 weeks. Routine postoperative examinations were scheduled at 1 day, 1 week, 1 month, 3 months, 6 months, and 1 year after surgery. The UCVA, spectacle-corrected visual acuity, and slit-lamp biomicroscopy were performed at the time of these examinations. Corneal topography was performed at the 1-month, 3-month, 6-month, and 1-year examinations. Nine patients had repeat specular microscopy performed 3 months after surgery.
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Results Twenty-three eyes of 22 patients (14 female, 8 male) underwent LASIK for visual rehabilitation after penetrating keratoplasty in a prospective, nonmasked clinical study. Mean age at the time of the LASIK surgery was 52.9 years (range, 27– 80 years). Mean time from penetrating keratoplasty to LASIK was 44.1 months (range, 8 –120 months), and mean time from suture removal of the penetrating keratoplasty to LASIK was 35.3 months (range, 3–108 months). All patients were spectacle correction-intolerant, and eight patients had attempted gas-permeable contact lens wear without success. The most common indication for the penetrating keratoplasty was keratoconus (13 eyes), followed by pseudophakic bullous keratopathy (5 eyes), Fuchs endothelial dystrophy with combined cataract extraction (3 eyes), herpes simplex keratitis (1 eye), and herpes zoster keratitis (1 eye). Fifteen eyes were phakic and 8 eyes were pseudophakic. There were no statistically significant differences in spherical or cylindrical correction among the three groups. Three patients had undergone corneal relaxing incisions for high cylinder after penetrating keratoplasty and antecedent to their LASIK surgery. The relaxing incisions were all performed more than 6 months before LASIK. The patients were followed for a mean of 7.6 months after LASIK (range, 1–14 months). All 23 patients were seen at 1-month follow-up, 22 patients at 3 months, 16 patients at 6 months, and 7 patients at 1 year. One patient was lost to follow-up after 1 month, and his data were included in the analysis. Patients were treated based on their refractive myopia and cylinder. Patients were treated with a range of 75% to 90% of their refractive sphere based on surgeon discretion. For the first eight cases, the patients were treated with between 75% and 82% of refractive sphere. When the surgeons recognized that these patients were being undercorrected, the patients were treated with between 84% and 90% of their preoperative sphere for subsequent cases. Patients were treated with 90% to 100% of their refractive cylinder to the maximum level of cylinder treatable with the VISX Star laser (Visx Inc, Santa Clara, CA) with current software limitations. In one case, the patient had 8.5 D of cylinder, and this patient was treated in a sequential manner, with 6 D being treated on the original treatment and 2.75 D treated with a subsequent enhancement. A total of two patients underwent enhancement: one patient was treated for residual cylinder and one patient was treated for myopic undercorrection. In both of these cases, the visual results after enhancement were used in the analysis of postoperative results.
Refractive Spherical Equivalent All patients were myopic in the operative eye, with a mean refractive spherical equivalent of ⫺7.58 ⫾ 4.42 D on cycloplegic or pseudophakic refraction. Patients were evaluated at 1 month, 3 months, 6 months, and 1 year after LASIK. Results are summarized in Figure 1. Twenty-three eyes had a mean sphere of ⫺1.09 D ⫾ 2.01 D at 1 month, 22 eyes had a mean sphere of ⫺0.79 D ⫾ 1.84 D at 3 months, 16 eyes had a mean sphere of ⫺0.77 D ⫾ 1.25 D at 6 months, and 7 eyes had a mean sphere of ⫺1.57 D ⫾ 1.20 D at 1 year. There was no statistical difference in the postoperative spherical equivalents at these four times (P ⫽ 0.632). At 3 months, two patients were greater than 1-D hyperopic, one patient was greater than 1-D hyperopic at 6 months, and none of the eight patients were hyperopic at the 1-year follow-up. Forty-three percent (10 of 23 eyes) were within 1 D of targeted sphere and 74% (17 of 23 eyes) were within 2 D of targeted sphere at 1-month follow-up. Fifty-nine percent (13 of 22 eyes) were
Donnenfeld et al 䡠 LASIK for Myopia and Astigmatism after Corneal Transplant
Figure 1. Mean deviation from intended spherical equivalent correction shown before surgery and at postoperative examinations. Numbers of patients examined at each visit are shown.
within 1 D of targeted sphere at 3 months after surgery, and 73% (16 of 22 eyes) were within 2 D of targeted sphere. At 6 months after surgery, 63% (10 of 16 eyes) were within 1 D of targeted sphere, and 88% (14 of 16 eyes) were within 2 D of targeted sphere. At 1 year, 43% (3 of 7 eyes) were within 1 D of targeted sphere, and 71% (5 of 7 eyes) were within 2 D of targeted sphere (Fig 2). In 2 of 22 patients, the targeted refraction was plano. In two patients, the goal of treatment was not plano due to myopia in the untreated eye and the desire to avoid anisometropia. In these two cases, the target refraction was 1 D of myopia less than the fellow eye. In these two patients, the spherical equivalent of the fellow eye was ⫺7.25 D and ⫺3.5 D. The last spherical equivalent of the treated eye in these two cases was ⫺6.75 D and ⫺2.8 D, respectively. In Figure 3, the spherical equivalent is based on the target refraction. In this figure, the target refraction is plano in 21 eyes and ⫺6.25 and ⫺2.5 in the 2 eyes that were purposely undercorrected.
Refractive Cylinder Mean refractive cylinder before surgery was 3.64 D ⫾ 1.72 D. Mean cylinder in 23 eyes is summarized in Figures 4 and 5. At 1-month follow-up, mean cylinder in 23 eyes was 1.98 D ⫾ 1.15 D. Mean cylinder at 3 months after surgery in 22 eyes was ⫺1.64
Figure 2. Percentage of patients within 1, 2, and 3 diopters of intended refractive spherical equivalent at given postoperative intervals. Emmetropia was the goal for all but two patients.
Figure 3. Scattergram of target vs. actual correction of spherical equivalent at final postoperative examination after laser in situ keratomileusis.
D ⫾ 1.14 D. Mean cylinder at 6 months after surgery was 1.48 D ⫾ 0.92 D in 16 eyes. At 1-year postoperative, mean cylinder was ⫺1.29 D ⫾ 1.04 D in seven eyes. There was no statistical difference between the postoperative cylinder results at the four time intervals (P ⫽ 0.543). At 3 months after surgery, 9 of 22 eyes had a refractive cylinder of less than 1 D, 18 of 22 eyes had a refractive cylinder of less than 2 D, and 20 of 22 eyes had a refractive cylinder of less than 3 D. At 6 months after surgery, 8 of 16 eyes had a refractive cylinder of less than 1 D, 12 of 16 eyes had a refractive cylinder of less than 2 D, and 16 of 16 eyes had a refractive cylinder of less than 3 D. At 1-year follow-up, four of seven patients had a refractive cylinder of less than 1 D, five of seven patients had a refractive cylinder of less than 2 D, and seven of seven eyes had a refractive cylinder of less than 3 D (Fig 6). Three patients had an increase in cylinder at their final examination compared to their preoperative cylinder. In no case was a decentered ablation based on corneal topography responsible for the increase in postoperative cylinder, and in all three of these cases, there was no progression of the cylinder during the postoperative course. These three patients had a preoperative mean cylinder of 1.83 D, which increased to a mean of 2.58 at the final examination after LASIK.
Visual Acuity Sixteen (70%) of 23 patients had best spectacle-corrected visual acuity (BSCVA) of 20/40 or greater before surgery. At 1 month
Figure 4. Mean cylinder shown before surgery and at postoperative examinations. Numbers of patients examined at each visit are shown.
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Ophthalmology Volume 106, Number 10, October 1999
Figure 5. Scattergram of target vs. actual correction of cylinder at final postoperative examination after laser in situ keratomileusis.
after LASIK, 16 (70%) of 23 had a BSCVA of 20/40 or greater. At 3 months, 15 (68%) of 22 eyes had a BSCVA of 20/40 or greater. At 6 months, 13 (81%) of 16 eyes had a BSCVA of 20/40 or greater. At 1 year, four (57%) of seven eyes had a BSCVA of 20/40 or greater. No patient lost UCVA. The preoperative UCVA ranged from 20/200 to counting fingers. At the final examination recorded, 8 (36%) of 22 eyes had a UCVA of 20/40 or greater, and 15 (68%) of 22 eyes had a UCVA of 20/70 or greater. In 9 eyes, BSCVA remained unchanged at the last visit after LASIK, while 12 eyes showed an improvement in BSCVA and 2 eyes showed a loss of BSCVA. Figure 7 shows lines of BSCVA and UCVA lost or gained. Figure 8 shows the percentage of patients with BSCVA of 20/25 or better, 20/40 or better, and 20/70 or better before LASIK and at their last visit after LASIK.
Anisometropia Before surgery, the mean difference in spherical equivalent between the patients’ operative eye and the fellow eye was 6.88 D ⫾ 4.4 D. The corneal transplant eye was always the more myopic eye. At the final postoperative refraction, this difference was reduced to 1.42 D ⫾ 1.05 D, a decrease of 79% (Fig 9). Eleven (50%) of 22 eyes were within 1 D, 17 eyes (77%) were within 2 D, 20 eyes (91%) were within 3 D, and all operative eyes were within 3.5 D of the untreated fellow eye (Fig 10).
Figure 6. Percentage of patients within 1, 2, and 3 diopters of intended refractive cylinder at given postoperative intervals. Zero cylinder was the goal for all patients.
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Figure 7. Gain and loss of visual acuity (Snellen lines). BSCVA ⫽ best spectacle-corrected visual acuity; UCVA ⫽ uncorrected visual acuity.
Corneal Transplant Complications The mean preoperative endothelial cell count in 9 patients was 1357, and at 3 months after surgery, the endothelial cell count in the same 9 patients was 1329. The endothelial cell counts are listed in Table 1. Mean endothelial cell loss was 2.1%, which is not statistically significant (P ⫽ 0.449). There were no wound dehiscences or flap complications. Specifically, there was no epithelial ingrowth, flap striae, free-flaps, or flap melts. No patient experienced a graft rejection episode after the LASIK surgery, and no patient had a loss of graft clarity. Two patients lost one or more lines of best-corrected visual acuity. One patient lost one line of visual acuity due to formation of a nuclear sclerotic cataract. The other patient lost three lines of visual acuity secondary to an increase in irregular astigmatism, which could not be spectacle corrected. This patient can now achieve 20/25 visual acuity with a gas-permeable contact lens.
Discussion The goal of therapeutic LASIK for visual rehabilitation after penetrating keratoplasty is not necessarily the same as LASIK for the correction of myopia, astigmatism, or both.
Figure 8. Percentage of patients within given ranges of best spectaclecorrected visual acuity before surgery and at final examination after laser in situ keratomileusis.
Donnenfeld et al 䡠 LASIK for Myopia and Astigmatism after Corneal Transplant Table 1. Pre- and Postoperative Endothelial Cell Counts
Figure 9. Mean anisometropia at preoperative and final postoperative examinations after laser in situ keratomileusis.
The primary goal of LASIK after penetrating keratoplasty is resolution of sufficient myopia and astigmatism to allow spectacle correction of the residual refractive error. The UCVA remains a secondary goal with LASIK after penetrating keratoplasty, whereas UCVA is clearly the primary objective of cosmetic LASIK. For this reason, return to binocularity and optimized best-corrected visual acuity with spectacles is the true endpoint for success with LASIK after penetrating keratoplasty. In our series, 21 of 22 patients were able to function binocularly with spectacles (17 of 22) or without correction (4 of 22). A major concern in performing LASIK after penetrating keratoplasty is the risk of damage to the corneal transplant or the graft– host–wound interface or both. Wound dehiscence after penetrating keratoplasty is a well-described phenomenon and can occur years after penetrating keratoplasty. In LASIK, the IOP is elevated to more than 65 mmHg, and there is a very small but very real risk of wound dehiscence with the possibility of extrusion of the intraocular contents. We recommend LASIK after penetrating keratoplasty be performed by experienced LASIK surgeons who can minimize the suction time needed during surgery. In our series, we experienced no wound complications. Unfortunately,
Figure 10. Distribution of anisometropia at the final postoperative examination after laser in situ keratomileusis.
Patient
Preoperative Endothelial Cell Count
Postoperative Endothelial Cell Count
1 2 3 4 5 6 7 8 9 Mean Standard deviation % Change P
1120 2040 975 1070 870 1450 890 1700 2100 1357.2 485.4 ⫺2.1 0.449753
1100 2100 850 1050 870 1400 870 1650 2070 1328.9 504.1
irregular as well as regular astigmatism is a common finding after penetrating keratoplasty. A potential advantage of LASIK is that there is evidence that the flap in LASIK creates a more regular ocular surface than occurs in PRK.28 Although irregular astigmatism can be a significant problem after LASIK for visual rehabilitation following penetrating keratoplasty, we believe there is less irregular astigmatism compared to PRK (Figs 11 and 12). In our series, one patient lost visual acuity due to increased irregular astigmatism. A second potential advantage of LASIK over surface excimer laser photoablation is that there is better corneal sensation after LASIK than after PRK.34 In LASIK, the 2 to 3 clock-hours of hinge nasally allows the passage of corneal nerves into the central cornea. This has been shown to provide improved sensation. One of the main predictors of graft survivability is corneal sensation. There is always a diminution of corneal sensation after penetrating keratoplasty due to trephination of the corneal nerves. LASIK offers an additional advantage over PRK in that there is less loss of corneal sensation. In our series, 19 of 23 patients continued to be myopic after LASIK. In two eyes, this was done purposefully to prevent anisometropia with the fellow eye. Additionally, our nomogram was less aggressive with our first eight patients. In general, we were comfortable leaving our patients mildly myopic and allowing them to be visually rehabilitated with spectacles, particularly when they wore spectacles for the other eye. The most common indication in the United States for penetrating keratoplasty is pseudophakic bullous keratopathy.35–37 There is a high incidence of macular pathology after penetrating keratoplasty for pseudophakic bullous keratopathy. Patients whose final visual rehabilitation is limited by macular pathology often are less motivated to wear contact lenses. Chronic cystoid macular edema is seen in 42% to 50% of cases of pseudophakic bullous keratopathy,38,39 and there is a 6% to 24% incidence of involutional macular degeneration after penetrating keratoplasty,40,41 both of which can severely limit visual rehabilitation. These patients may have a best-corrected visual acuity ranging from 20/25 to counting fingers, with the majority having
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Ophthalmology Volume 106, Number 10, October 1999 visual acuities of 20/40 or less. Price et al14 reported that only 50% of patients with grafts for pseudophakic bullous keratopathy achieved a visual acuity of 20/40 or better, whereas Zaidman and Goldman42 reported 31% and Speaker et al43 reported a 22% incidence of visual acuity of 20/40 or better after penetrating keratoplasty for pseudophakic bullous keratopathy. Pseudophakic bullous keratopathy occurs overwhelmingly in an elderly population. Assuming these patients have good visual acuity in their fellow eye, there may be little motivation for an elderly individual, with no possibility of visual rehabilitation to the level of the fellow eye, to wear a soft or gas-permeable contact lens. These patients have had previous cataract surgery, penetrating keratoplasty, approximately 1 year of postoperative visits before suture removal, and, often, a vitreoretinal consultation. When they are ready for their visual rehabilitation, patients are told they cannot be improved with spectacles because of significant anisometropia. Even though their central visual acuity may be diminished, these patients would benefit greatly from the expanded peripheral visual field. These patients are excellent candidates for postpenetrating keratoplasty LASIK, which can offer permanent rehabilitation of their refractive error. There are several alterations of our normal LASIK technique when treating myopia or astigmatism or both after penetrating keratoplasty. An accurate assessment of the patient’s true refraction depends on the donor cornea returning to its normal shape after suture removal. With gaspermeable contact lens wear, most LASIK surgeons recommend a minimum of 1 month to allow resolution of corneal warpage, and with long-term gas-permeable contact lens wear, the corneal warpage may take several months to abate. We chose to wait a minimum of 6 months after suture removal before LASIK in all but one patient. In our series, the mean time from penetrating keratoplasty to LASIK was 44 months, and the mean time from suture removal was 34 months. We recommend this prolonged period to allow the corneal wound to equilibrate completely. More important, we are concerned with the ability of the corneal transplant
wound to withstand the elevated IOP of the suction head. In LASIK, IOP is elevated to at least 65 mmHg to draw the cornea into the circular opening and firmly hold it in place while the microkeratome creates a surgical flap. Inadequate pressure will predispose to flap complications, such as free flaps, thin flaps, and buttonholes. A corneal transplant wound is never as secure as a normal cornea, but we suggest that allowing 6 months after suture removal will provide additional time for wound healing to occur. In our series, there were no complications related to the increased IOP of LASIK and, specifically, no wound dehiscences. The surgical LASIK procedure we used was our standard technique, altered only to avoid initiating the incision at the corneal transplant graft– host interface. The patients’ donor corneas ranged in size from 7.75 to 8.5 mm in diameter. The flap diameter created by the automated corneal shaper is approximately 8.5 mm. Therefore, the flap is almost exactly the same size as the donor cornea. We avoided initiating the flap temporally at the graft– host interface while attempting to center the flap over the pupil. We also tried to begin the incision 1 mm temporal or 1 mm nasal to the temporal aspect of the graft– host interface based on centration of the corneal transplant over the pupil. Doing this allowed the flap to drape over the wound. We believe this creates better wound apposition of the flap to the recipient bed. The corneal scar tissue at the penetrating keratoplasty wound tends to be less pliable than normal corneal tissue. In addition, initiating the LASIK incision temporally prevents applying additional pressure directly to the corneal transplant wound and may decrease the risk of wound dehiscence. After repositioning the corneal flap, we generally wait 2 minutes for the flap to adhere to the underlying stromal bed. This is altered in LASIK after penetrating keratoplasty, where we wait 5 minutes for flap adherence before removing the speculum. We are also more liberal with our use of postoperative corticosteroids than in our normal LASIK patients. We use fluorometholone 0.1% four times daily for 5 days after conventional LASIK surgery. In LASIK after penetrating keratoplasty, we used prednisolone acetate 1% four times daily for 1 week and then pred-
Figure 11. Corneal topography of a patient before undergoing laser in situ keratomileusis.
Figure 12. Post laser in situ keratomileusis corneal topography for same patient shown in Figure 11.
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Donnenfeld et al 䡠 LASIK for Myopia and Astigmatism after Corneal Transplant nisolone acetate 1% once daily for 2 weeks. We believe the additional use of corticosteroids is indicated because of the potential risk of graft rejection after any surgical procedure on a penetrating keratoplasty. In our series, we experienced no episodes of graft rejection. After penetrating keratoplasty, many patients will have irregular astigmatism, which, although not amenable to spectacle correction, can be rehabilitated with a gas-permeable contact lens. We discourage these patients if they are at all contact lens-tolerant from having LASIK performed, as the Excimer Laser (VISX, Inc) currently is not successful in treating irregular astigmatism. The VISX Star Laser creates a 6-mm-ablation zone for up to 6 D of myopia in the corneal plane, decreasing to 5 mm with a single-pass multizone technology. Although this technology is excellent for regular astigmatism and myopia, it cannot currently treat irregular astigmatism. We anticipate that the development of flying spot Excimer Lasers guided by corneal topography will successfully treat some forms of irregular astigmatism in the next several years. This will allow even more accurate treatment of postpenetrating keratoplasty refractive errors. Although we only treated myopia and myopic astigmatism, LASIK also may be effective in the treatment of hyperopia and hyperopic astigmatism, although their larger peripheral ablations may impact directly on the corneal transplant wound. In conclusion, LASIK is successful in treating postkeratoplasty myopia and astigmatism in most patients. Patients were overwhelmingly able to resolve their anisometropia and achieve binocular function. LASIK was more effective in treating residual myopia than astigmatism. We advocate a conservative approach to treating refractive errors after penetrating keratoplasty with LASIK. Contact lenses remain the standard of care and are to be encouraged whenever feasible. When contact lens use is not possible, we suggest slightly undercorrecting the myopia, especially when the fellow eye is myopic. Return to binocularity is the primary goal of treatment. In addition, LASIK offers the advantage of allowing enhancements at a later date for residual refractive errors. LASIK offers the corneal surgeon an additional tool in the visual rehabilitation of the corneal transplant patient.
References 1. Statistical Report, Eye Bank Association of America, 101 Connecticut Avenue, N.W., Suite 601, Washington, DC 20306, 1993. 2. Brooks SE, Johnson D, Fischer N. Anisometropia and binocularity. Ophthalmology 1996;103:1139 – 43. 3. Rubin ML. Anisometropia. In: Fraunfelder FT, Hampton Roy F, eds; Grove J, assoc. ed. Current Ocular Therapy 4. Philadelphia: Saunders, 1995;757– 8. 4. Perl T, Charlton KH, Binder PS. Disparate diameter grafting. Astigmatism, intraocular pressure, and visual acuity. Ophthalmology 1981;88:774 – 81. 5. Flowers CW, McCleod SD, McDonnell PJ, et al. Evaluation of intraocular lens power calculation formulas in the triple procedure. J Cataract Refract Surg 1996;22:116 –22.
6. Perlman EM. An analysis and interpretation of refractive errors after penetrating keratoplasty. Ophthalmology 1981;88: 39 – 45. 7. Clinch TE, Thompson HW, Gardner BP, et al. An adjustable double running suture technique for keratoplasty. Am J Ophthalmol 1993;116:201– 6. 8. Binder PS. The effect of suture removal on postkeratoplasty astigmatism. Am J Ophthalmol 1988;105:637– 45. 9. Samples JR, Binder PS. Visual acuity, refractive error, and astigmatism following corneal transplantation for pseudophakic bullous keratopathy. Ophthalmology 1985;92:1554 – 60. 10. Assil KK, Zarnegar SR, Schanzlin DJ. Visual outcome after penetrating keratoplasty with double continuous or combined interrupted and continuous suture wound closure. Am J Ophthalmol 1992;114:63–71. 11. Binder PS. Intraocular lens powers used in the triple procedure. Effect on visual acuity and refractive error. Ophthalmology 1985;92:1561– 6. 12. Davis EA, Azar DT, Jakobs FM, Stark WJ. Refractive and keratometric results after the triple procedure. Experience with early and late suture removal. Ophthalmology 1998;105:624 – 30. 13. Lopatynsky MO, Cohen EJ. Post-keratoplasty fitting for visual rehabilitation. In: Kastl PR, ed. Contact Lenses: The CLAO Guide to Basic Science and Clinical Practice. Dubuque, Iowa: Kendall/Hunt Pub. Co., 1995;79 –90. 14. Price FW Jr, Whitson WE, Marks RG. Progression of visual acuity after penetrating keratoplasty. Ophthalmology 1991;98: 1177– 85. 15. Speaker MG, Cohen EJ, Edelhauser HF, et al. Effect of gas-permeable contact lenses on the endothelium of corneal transplants. Arch Ophthalmol 1991;109:1703– 6. 16. Troutman RC. Corneal wedge resections and relaxing incisions for postkeratoplasty astigmatism. Int Ophthalmol Clin 1983;23:161– 8. 17. Lugo M, Donnenfeld ED, Arentsen JJ. Corneal wedge resection for high astigmatism following penetrating keratoplasty. Ophthalmic Surg 1987;18:650 –3. 18. Maguire LJ, Bourne WM. Corneal topography of transverse keratotomies for astigmatism after penetrating keratoplasty. Am J Ophthalmol 1989;107:323–30. 19. Kirkness CM, Ficker LA, Steele AD, Rice NS. Refractive surgery for graft-induced astigmatism after penetrating keratoplasty for keratoconus. Ophthalmology 1991;98:1786 –92. 20. Waring GO III, Lynn MJ, Gelender H, et al. Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study one year after surgery. Ophthalmology 1985;92:177–98, 307. 21. Gothard TW, Agapitos PJ, Bowers RA, et al. Four-incision radial keratotomy for high myopia after penetrating keratoplasty. Refract Corneal Surg 1993;9:51–7. 22. Ficker LA, Kirkness CM, Steele AD. Intraocular surgery following penetrating keratoplasty: the risks and advantages. Eye 1990;4:693–7. 23. Campos M, Hertzog L, Garbus J, et al. Photorefractive keratectomy for severe post-keratoplasty astigmatism. Am J Ophthalmol 1992;114:429 –36. 24. Amm M, Duncker GI, Schroder E. Excimer laser correction of high astigmatism after keratoplasty. J Cataract Refract Surg 1996;22:313–7. 25. Maloney RK, Chan WK, Steinert R, et al. A multicenter trial of photorefractive keratectomy for residual myopia after previous ocular surgery. Summit Therapeutic Refractive Study Group. Ophthalmology 1995;102:1042–52; discussion, 1052–3.
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Ophthalmology Volume 106, Number 10, October 1999 26. Lazzaro DR, Haight DH, Belmont SC, et al. Excimer laser keratectomy for astigmatism occurring after penetrating keratoplasty. Ophthalmology 1996;103:458 – 64. 27. Pallikaris IG, Papatzanaki ME, Stathi EZ, et al. Laser in situ keratomileusis. Lasers Surg Med 1990;10:463– 8. 28. Hersh PS, Brint SF, Maloney RK, et al. Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia. A randomized prospective study. Ophthalmology 1998;105:1512–22; discussion, 1522–3. 29. Helmy SA, Salah A, Badawy TT, Sidky AN. Photorefractive keratectomy and laser in situ keratomileusis for myopia between 6.00 and 10.00 diopters. J Refract Surg 1996;12:417– 21. 30. Salah T, Waring GO III, el-Maghraby A, et al. Excimer laser in-situ keratomileusis (LASIK) under a corneal flap for myopia of 2 to 20 D. Trans Am Ophthalmol Soc 1995;93:163– 83; discussion, 184 –90. 31. Azar DT, Farah SG. Laser in situ keratomileusis versus photorefractive keratectomy. An update on indications and safety. Ophthalmology 1998;105:1357– 8. 32. Arenas E, Maglione A. Laser in situ keratomileusis for astigmatism and myopia after penetrating keratoplasty. J Refract Surg 1997;13:27–32. 33. Zaldivar R, Davidorf J, Oscherow S. LASIK for myopia and astigmatism after penetrating keratoplasty. J Refract Surg 1997;13:501–2. 34. Kanellopoulos AJ, Pallikaris IG, Donnenfeld ED, et al. Comparison of corneal sensation following photorefractive keratectomy and laser in situ keratomileusis. J Cataract Refract Surg 1997;23:34 – 8.
35. Corneal Transplant Recipient Diagnosis Report. 1993; 1993 Statistical Report. Eye Bank Association of America, 1001 Connecticut Avenue, N.W., Suite 601, Washington, DC 20030. 36. Brady SE, Rapuano CJ, Arentsen JJ, et al. Clinical indications for and procedures associated with penetrating keratoplasty, 1983–1988. Am J Ophthalmol 1989;108:118 –22. 37. Mamalis N, Anderson CW, Kreisler KR, et al. Changing trends in the indications for penetrating keratoplasty. Arch Ophthalmol 1992;110:1409 –11. 38. Heidemann DG, Dunn SP. Transsclerally sutured intraocular lenses in penetrating keratoplasty. Am J Ophthalmol 1992; 113:619 –25. 39. Kornmehl EW, Steinert RF, Odrich MG, Stevens JB. Penetrating keratoplasty for pseudophakic bullous keratopathy associated with closed-loop anterior chamber intraocular lenses. Ophthalmology 1990;97:407–12; discussion, 413– 4. 40. Holland EJ, Daya SM, Evangelista A, et al. Penetrating keratoplasty and transscleral fixation of posterior chamber lens. Am J Ophthalmol 1992;114:182–7. 41. Gaster RN, Ong HV. Results of penetrating keratoplasty with posterior chamber intraocular lens implantation in the absence of a lens capsule. Cornea 1991;10:498 –506. 42. Zaidman GW, Goldman S. A prospective study on the implantation of anterior chamber intraocular lenses during keratoplasty for pseudophakic and aphakic bullous keratopathy. Ophthalmology 1990;97:757– 62. 43. Speaker MG, Lugo M, Laibson PR, et al. Penetrating keratoplasty for pseudophakic bullous keratopathy. Management of the intraocular lens. Ophthalmology 1988;95:1260 – 8.
Discussion by Jonathan H. Talamo, MD Donnenfeld and colleagues report data from the first sizable series of laser in situ keratomileusis (LASIK) treatments after penetrating keratoplasty (PK). In doing so, the authors provide preliminary evidence that LASIK is an effective tool to reduce post-PK ametropia, particularly if the clinical endpoint is improved spectacle tolerance rather than excellent uncorrected visual acuity. However, before discussing the promising implications of these results, it is important to remind the reader of the limitations of this type of clinical study. As with many case series, it is not prospective, nonrandomized, and has a small sample size. Because follow-up is limited (the majority of eyes were examined for only 3 months after surgery), the refractive stability of the procedure and the subsequent health of the corneal graft in this setting have not been unequivocally established. Additional shortcomings of this case series include the very wide range of refractive errors studied and the variation in best spectacle-corrected visual acuity (BSCVA) recorded before surgery. Thirty percent of eyes had BSCVA of 20/40 or worse before LASIK, and as such, it may have been difficult to obtain an accurate preoperative manifest refraction. Although such findings are not unexpected in eyes that have undergone corneal transplantation, it is difficult to draw conclusions about exactly when and how LASIK is most effective in this setting.
From Cornea Consultants, Boston, and the Laser Eye Center of Boston, Boston, Massachusetts. Address correspondence to Jonathan H. Talamo, MD, Cornea Consultants, 100 Charles River Plaza, Boston, MA 02114. E-mail: [email protected].
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Table 1. Surgery for Ametropia after PK BSCVA Loss ⱖ 2 Lines Author Lazzaro Amm Campos Donnenfeld Hersh
Procedure
Percent
Reference
PRK/PARK
0–38
Ophtha 1996 JCRS 1996 AJO 1992
LASIK PRK/PARK LASIK
4.3 12 3
Ophth 1998
Previous reports have established that photorefractive keratectomy (PRK) and photoastigmatic refractive keratectomy (PARK) can significantly reduce residual ametropia after PK.1–3 However, the safety, efficacy, and predictability of surface ablation decrease when used for the high degrees of refractive correction necessary,4 which may render PRK/PARK much less useful in this setting. As the authors demonstrate, the incidence of BSCVA loss of two or more Snellen lines generally is much higher after PRK than for LASIK, regardless of whether the procedure is performed after PK or for naturally occurring refractive error (Table 1). In addition to BSCVA loss, other safety issues raised by the authors include the risk of wound rupture and graft rejection. The possibility of suction-related retinal vascular or optic nerve compromise should also be considered, particularly if the patient is older or has a history of such conditions. The treatment of surgically induced astigmatism after PK remains a major challenge, and the results presented in this article do not represent a significant improvement in this area. Table 2
Donnenfeld et al 䡠 LASIK for Myopia and Astigmatism after Corneal Transplant Table 2. Surgery for Ametropia after PK Astigmatism Reduction Author Lazzaro Amm Campos Donnenfeld Kirkness
Procedure PRK/PARK LASIK AK/CS
Percent 38–57 55 46
Eyes (n) 7 16 12 22 (3 mo) 42
provides a summary of mean postkeratoplasty astigmatism after incisional5 and photorefractive procedures1–3 as reported in representative studies in the peer-reviewed literature. I agree with the authors that difficulties in accurately measuring refractive cylinder due to irregular astigmatism and decreased BSCVA as well as the long-term instability of PK wounds continue to be major obstacles to improved results. Hopefully, the ability to perform larger diameter lamellar keratectomy resections and custom ablations with flying spot lasers will yield progress. It seems reasonable to conclude that in carefully selected patients with well-healed corneal transplant wounds and minimal irregular astigmatism, LASIK performed by an experienced sur-
geon will safely and effectively reduce ametropia after PK for the purpose of improved spectacle tolerance. A much larger cohort of patients will be necessary to establish the true incidence of flap and graft-related complications. References 1. Campos M, Hertzog L, Garbus J, et al. Photorefractive keratectomy for severe postkeratoplasty astigmatism. Am J Ophthalmol 1992;114:429 –36. 2. Lazzaro DR, Haight DH, Belmont SC, et al. Excimer laser keratectomy for astigmatism occurring after penetrating keratoplasty. Ophthalmology 1996;103:458 – 64. 3. Amm M, Duncker GI, Schroder E. Excimer laser correction of high astigmatism after keratoplasty. J Cataract Refract Surg 1996;22:313–7. 4. Hersh PS, Brint SF, Maloney RK, et al. Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia. A randomized prospective study. Ophthalmology 1998;105:1512–22; discussion, 1522–3. 5. Kirkness CM, Ficker LA, Steele AD, Rice NS. Refractive surgery for graft-induced astigmatism after penetrating keratoplasty for keratoconus. Ophthalmology 1991;98:1786 –92.
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