Incidence and management of intraoperative and early postoperative complications in 1000 consecutive laser in situ keratomileusis cases

Incidence and Management of Intraoperative and Early Postoperative Complications in 1000 Consecutive Laser In Situ Keratomileusis Cases Howard V. Gimbel, MD, MPH, Ellen E. Anderson Penno, MD, MS, John A. van Westenbrugge, MD, Maria Ferensowicz, MA, Michael T. Furlong, MD Objective: To identify intraoperative and early postoperative complications of laser in situ keratomileusis (LASIK) surgery learning curve and to offer recommendations on prevention and management. Design: Retrospective noncomparative case series. Participants: The first 1000 consecutive myopic LASIK eyes (April 1995–February 1997) operated on by one surgeon (HVG) were examined. Intervention: Myopic LASIK surgery was performed with the Chiron Corneal Shaper and NIDEK EC-5000 excimer laser. Main Outcome Measures: The preoperative and 6-month postoperative spherical equivalent, best-corrected visual acuity, and corneal status were recorded, as was the incidence of intraoperative and early postoperative complications. The rate of retreatments was also recorded. Results: There were 32 (3.2%) intraoperative complications and surgical events recorded, including 19 (1.9%) microkeratome-related flap complications and 13 (1.3%) nonmicrokeratome-related surgical events such as inability to obtain sufficient suction. There were 18 (1.8%) postoperative complications requiring repositioning of microwrinkled or shifted flaps. Six-month spherical equivalent was ⫺0.52 diopter [D] ⫾ 1.19 D for eyes with microkeratome complications, ⫺0.56 D ⫾ 1.07 D for the group with nonmicrokeratome-related intraoperative events, and ⫺0.78 D ⫾ 0.92 for eyes requiring postoperative flap repositioning. None of the 32 eyes with intraoperative complications and surgical events lost 2 or more lines of vision. One eye in the postoperative complications group lost two lines of vision. The rate of microkeratome complications related to surgical technique and the overall surgery times decreased over the course of the first 1000 myopic LASIK cases. Conclusion: The complications encountered during the early learning curve of LASIK surgery have not in this series resulted in a significant loss of best-corrected visual acuity. With increasing surgical experience, the incidence of complications, along with surgical times, has decreased. Ophthalmology 1998;105:1839 –1848 Laser in situ keratomileusis (LASIK)1 is gaining in popularity worldwide for the correction of myopia, hyperopia, and astigmatism. The rapid recovery of vision and high patient satisfaction have led many surgeons to cite LASIK as their procedure of choice for both primary and repeat refractive surgeries. Because using an automated microkeratome to create a lamellar corneal incision is a new procedure for most surgeons, a definite learning curve associated with LASIK has been reported by our group and others.2– 4 Our current technique for standard LASIK surgery using the Chiron Corneal Shaper microkeratome (Chiron Vision Corp., Irvine, CA) has evolved since our first case on April 26, 1995. This article updates our technique

Originally received: October 26, 1997. Revision accepted: March 10, 1998. Manuscript no. 97543. From Gimbel Eye Centre, Calgary, Alberta, Canada. Reprint requests to Howard V. Gimbel, MD, MPH, 450, 4935 - 40 Avenue NW, Gimbel Eye Centre, Calgary, Alberta, Canada T3A 2N1.

and reports intraoperative and postoperative complications and surgery times of the first 1000 consecutive myopic LASIK cases performed by 1 surgeon (HVG). Recommendations are made for preventing and managing complications.

Materials and Methods Data Collection Charts for the first 1000 consecutive myopic LASIK cases, April 1995 to February 1997, performed by 1 surgeon (HVG) were reviewed for the surgical times and for the incidence of intraoperative and postoperative complications. This retrospective study was facilitated by an electronic online medical record system for recording preoperative, intraoperative, and postoperative patient data that has been in place since 1986. Outcome measures for this series included preoperative and postoperative spherical equivalents, targeted spherical equivalent, surgical times, intraoperative

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Ophthalmology Volume 105, Number 10, October 1998 surgical events and complications, postoperative complications, preoperative and postoperative best-corrected visual acuity (BCVA), and incidence of retreatments.

Preoperative Assessment and Criteria At our center, LASIK has been limited to patients 18 years of age or older. Patients with myopia were required to have had stable refractions. Preoperative BCVA was 20/40 or better in both eyes except in two eyes with myopic degeneration. A complete ocular and medical history was obtained with special attention to the presence of collagen vascular disease, hormonal changes such as pregnancy, previous refractive or other anterior segment surgery, ocular injuries, and vitreoretinal surgery or disease. Medications and allergies also were noted. In addition, an assessment of motivations and expectations was made to determine whether patient objectives would be satisfactorily addressed by LASIK. After detailed instruction and discussion, written consent was obtained. Patients wearing contact lenses were generally asked to leave soft lenses out for at least 48 hours and hard contact lenses including rigid gas-permeable lenses out for 2 weeks before surgery. All patients received the following tests before surgery: lensometry, autorefractometry, autokeratometry, manual keratometry, corneal topography, determination of eye dominance, visual acuity (VA) with and without correction, manifest and usually cycloplegic refraction with vertex distance measurement, measurements for ptosis, pupil diameter in normal and dim light, measurement of intraocular pressure (IOP), pachymetry (must be at least 500 ␮m to proceed if myopia is ⬎10 diopters [D]), notation of palpebral fissure size if narrow, corneal diameter measurements, slit-lamp examination, and dilated fundus examination including scleral-depressed peripheral retinal examination in patients with high myopia. Specular microscopy, pachymetry, and A-scan also were performed in cases of high myopia.

Surgical Technique The surgical techniques described below represent modifications made on the LASIK techniques as experience was gained. All 1000 cases reported in this article were done with the NIDEK EC-5000 Excimer Laser (Nidek Co. Ltd., Gamagari, Japan). All but one case was performed with the Chiron microkeratome, and all cuts were made at a corneal depth of 160 ␮m. Preoperative myopia ranged from ⫺1.00 D to ⫺23.00 D, and all patients received tobramycin– dexamethasone four times a day for 1 week after surgery. A gown, cap, mask, and sterile lint-free gloves were worn by the surgeon and assistant or assistants. Preoperative sedation was given as needed of either diazepam 10 mg orally, lorazepam 1 mg sublingual, or alprazolam 0.5 mg 30 minutes before the procedure. Proparacaine 0.5% was given in three applications starting not more than 10 minutes before LASIK. Inspection of the suction ring and microkeratome was performed by the assistant according to rigid criteria, followed by inspection under the microscope by the surgeon before proceeding with LASIK. Laser treatment parameter input was double checked, and the patient was prepared with povidone–iodine 5%, draped, and the speculum was inserted carefully. These steps were performed with particular attention to head and eye position and globe exposure, as will be discussed later. Gentian violet marking, suction ring placement, and microkeratome cut have been described previously.2 After the microkeratome cut, the flap was turned onto a cut tip of Merocel sponge (Merocel Corp., Mystic, CT) and smoothed before the ablation to avoid wrinkling. Care was taken to not waste time between turning the flap and starting the ablation and to standardize this time to

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Table 1. Demographic Data and Preoperative Refraction Profile Variable Total no. of patients Total primary myopic cases Gender Male Female Age at surgery (yrs) Mean Range Median Refractive error (D) Mean Range ⬎20.00 15.00–20.00 10.00–14.99 ⬍10.00

No. 523 1000 245 278 33.1 19–67 35 ⫺9.56 ⫺1.00 to ⫺23.00 8 55 319 618

avoid variability of results due to drying of the tissue. After the ablation, the flap was repositioned on the dry stromal bed and then floated with gentle irrigation after removal by irrigation of any large air bubbles. A dripping-wet Merocel sponge was then used to gently express fluid from the interface. The slit beam of the NIDEK laser (with coaxial and room lights off) was used to inspect carefully for wrinkles and interface debris. The patient was inspected again 25 to 45 minutes after LASIK with standard slit-lamp biomicroscopy to check for the presence of wrinkles or interface debris and to ensure continued good flap position after resumption of normal blinking. After surgery, the patient was reminded to not touch or rub the eye. Artificial tears were given to be used liberally, and tobramycin– dexamethasone every 6 hours for 1 week was prescribed. Patients were examined at 1 day, 1 week, 1 month, 3 months, and 6 months. If needed, enhancements were performed as early as 1 week; however, the time to enhancement averaged approximately 5 months after initial LASIK surgery. Visual and refractive results are reported with a minimum of 1 month after the last enhancement was done.

Results Patient Demographics One thousand primary myopic LASIK cases performed on 523 patients were reviewed (Table 1). There were similar numbers of males and females, and the mean age at time of surgery was 33.1 years. The mean preoperative spherical equivalent was ⫺9.56 D with a range of ⫺1.00 D to ⫺23.00 D. The majority of cases (93.7%) were ⫺15.00 D or less before surgery, with 618 of 1000 eyes less than ⫺10.00 D before surgery and 63 eyes with greater than ⫺14.99 D of preoperative myopia (Table 1). Two hundred forty-one patients had LASIK performed bilaterally on the same day, 236 patients had the second surgeries performed on different days with a mean time of 28.6 days between eyes, and 46 patients had unilateral LASIK performed (Table 2). The number of right and left eyes in the unilateral cases was roughly equal. There were 87 lateral canthotomy procedures performed.

Gimbel et al 䡠 Management of LASIK Complications Table 2. Characteristics of First 1000 Myopic Primary LASIK Cases Variable No. of eyes OD OS No. of bilateral cases Same day Different days (mean 28.6 days between eyes) No. of unilateral cases No. of lateral canthotomies

No. 496 504 241 patients (482 eyes) 236 patients (472 eyes) 46 patients (46 eyes) 87

Intraoperative and Early Postoperative Complications Thirty-two intraoperative complications and events were recorded in the first 1000 myopic LASIK cases. These included 19 microkeratome complications as well as 13 surgical events (Table 3). Thirteen (68.4%) of the 19 microkeratome complications involved the right eye (Fisher exact test, P ⫽ 0.025). The majority of microkeratome complications were incomplete passes (12) with a lower rate of thin flaps (3), and buttonholes (3), and only a single free cap. Intraoperative surgical events recorded included insufficient suction and IOP elevation (5), bleeding from cut limbal arcade vessels (3), epithelial bullae and torn epithelium (2), dislodged flap during speculum removal (2), and one flap shrinkage that was sutured. Of the 13 eyes with intraoperative surgical events and complications, LASIK proceeded as scheduled in 10 of these eyes (Table 4). The remaining three eyes, all with insufficient suction and IOP elevation, had LASIK canceled initially. Of those three eyes, the first eye had LASIK at a later date because the initial failure was caused by conjunctival entrapment in the suction port. Once this happens, the edematous conjunctiva keeps coming to the port and time is required before LASIK can be performed successfully. The second eye had PRK and the third eye had lensectomy. Both of these eyes had previous scleral buckling surgery—a high risk for not being able to get sufficient suction and IOP elevation (Table 4). For the group with microkeratome complications, surgery was discontinued initially in 10 of the 19 eyes: 8 of those 10 went on to have LASIK at a later date, and 2 currently are considering lensectomy or phakic IOLs (Table 4). The nine completed eyes had further dissection of the flap because the cut stopped within 1.0 mm of the edge of the planned ablation zone. The mean time between the initial failed surgery and later successful LASIK surgery was 3.25 months. Eighteen eyes in this series required flap repositioning within the first 24 hours after surgery. These included 12 shifted flaps (3 of which required suturing), 4 microwrinkles, and 2 edge folds (Table 5). Of the 12 shifted flaps, 1 was as a result of prominent exophthalmos with poor blink reflex, 1 was because of lagophTable 3. Microkeratome Complications and Surgical Events (n ⫽ 32; 3.2%) Microkeratome Complications (n ⴝ 19) Incomplete pass 12 Thin flap 3 Button hole 3 Free cap 1

Table 4. Microkeratome Complications and Surgical Events*

Surgical Events (n ⴝ 13) Insufficient suction 5 Bleeding pannus 3 Epithelial bullae 2 Flap dislodged 2 Flap shrinkage 1

Insufficient suction (n ⫽ 5) Incomplete pass (n ⫽ 12) Button hole (n ⫽ 3) Thin flap (n ⫽ 3)

Discontinued Initially

Successfully Performed Later

3/5 6/12 3/3 1/3

1/3 5/6 2/3 1/1

* In the group with surgical events 3 of the 13 had LASIK discontinued initially and 1 of those 3 had LASIK at a later date; all 3 cases in which surgery was halted were due to insufficient suction. Ten of the 19 cases with intraoperative microkeratome complications had surgery canceled and 8 of that 10 had LASIK at a later date. Of the total of 4 cases in which LASIK was not performed 1 had PRK, 1 had AK and lensectomy, and 2 have not had refractive surgery performed to date. The mean time between surgeries was 3.25 months for those cases who had LASIK discontinued initially and performed at a later date.

thalmos and an incomplete blink in an eye with previous trauma, and 2 eyes of 1 patient because of dislodged flaps subsequent to extremely loose and torn epithelium after the microkeratome pass. The latter 3 eyes ultimately required sutures to secure the flaps after repositioning. The quarterly report of complications shows a decrease in the incidence of intraoperative microkeratome complications in later surgeries (Table 6). This decline is even more evident when viewed per 200 cases; the rate of microkeratome complications decreased from 4.5% for the first 200 cases to 0.5% in the latest 200 eyes (chi-square, P ⫽ 0.01) (Fig 1). The incidence of 6 complications in the first 200 cases compared to 0 complication by the 800th case also was statistically significant (chi-square, P ⫽ 0.002). There was no statistically significant difference in the incidence of microkeratome complications between the last 3 groups of 200 cases. In addition, both the mean time and range of time from turning of the flap to onset of ablation declined from the first 200 to the last 200 eyes (Fig 2). The overall time to perform LASIK was also shortened (Fig 3). Twenty-nine percent of the first 950 myopic LASIK eyes without intraoperative or postoperative complications underwent retreatment procedures for refractive reasons with a mean time between initial surgery and enhancement of 5.1 months (range, 9 days–20.3 months; Table 7). Because of the early experience of LASIK with the NIDEK laser and lack of algorithm development, especially in the high myopic group, the majority of retreatments were performed for primary undercorrection. Two (10.5%) of the 19 eyes with microkeratome complications required retreatment: 1 was for undercorrection and 1 for epithelial ingrowth (mean time to retreatment, 7.5 months). In the group with other intraoperative events, 3 (23%) of 13 had refractive retreatments with a mean time to retreatment of 8 months, 2 of which were for undercorrection and 1 for overcorrection. Six (33.3%) of 18 eyes that required postoperative flap repositioning underwent retreatment with a mean time of 3.6 months; retreatment was done for 1 case each of regular astigmatism, irregular astigmatism, interface debris, overcorrection, and two eyes for undercorrection. Retreatment rates are summarized in Table 7. Reasons for retreatments in eyes without Table 5. Perioperative Flap Repositioning (n ⫽ 18; 1.8%) n Shifted flap Microwrinkles Edge fold

12 4 2

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Ophthalmology Volume 105, Number 10, October 1998 Table 6. Quarterly Rate of Microkeratome Complications* (n ⫽ 1000)

May–Jun 95 Jul–Sep 95 Oct–Dec 95 Jan–Mar 96 Apr–Jun 96 Jul–Sep 96 Oct–Dec 96 Jan–Feb 97 Total

No.

%

0/28 2/44 6/53 1/55 4/140 4/234 1/280 1/156 19/1000

0.0 4.6 11.3 1.8 2.9 1.7 0.4 0.6 1.9

* The rate of intraoperative microkeratome complications was tracked quarterly and shows a decreasing trend as experience is gained. The first and last quarters were only 2 months because of the timing of the study.

Figure 1. The quarterly rate of intraoperative microkeratome complications declined over the first 1000 myopic laser in situ keratomileusis cases.

Discussion intraoperative or postoperative complications are outlined in Table 8.

Postoperative Best-corrected Visual Acuity and Spherical Equivalent At 6 months after surgery, 26 (81.25%) of 32 eyes with intraoperative microkeratome complications or events maintained or gained 1 line of BCVA, with a total of 6 (18.75%) losing 1 line and none losing 2 or more lines of BCVA (Table 9). Sixteen (1.77%) eyes in the group without intraoperative or postoperative complications lost 2 or more lines of BCVA. The reasons for loss in BCVA were microwrinkling (n ⫽ 6), interface haze (n ⫽ 6), and corneal edema (n ⫽ 4). This was a cross-section review of 906 patients with a variant follow-up of 3.8 months ranging from 3 weeks’ to 17 months’ follow-up. All 16 cases presenting with loss of ⱖ2 lines of BCVA occurred less than 3 months after surgery. Similarly, the majority (77.8%) of eyes requiring postoperative flap repositioning maintained the same BCVA or gained one line of BCVA at 6 months (Table 9). The eye that lost two lines was one with extremely loose epithelium in both eyes that, despite a bandage contact lens, had a dislodged flap develop immediately after surgery that required suturing. The patient’s other eye also required suturing but has lost only one line. Both eyes have persistent punctate epithelial staining. Of the remaining 950 eyes without intraoperative events and complications or postoperative flap repositioning, follow-up was available in 906 eyes; mean follow-up in these 906 cases was 3.8 months (range, 1–22 months). The overall BCVA remained excellent in these 906 eyes with 93.3% of eyes maintaining or gaining lines of BCVA (Table 9). Overall, of these 906 eyes, 796 eyes (87.8%) were within ⫾1 D of targeted spherical equivalent, and 557 eyes (61.5%) were within ⫾0.5 D (Table 10). Of the eyes with microkeratome complications, 13 eyes (76.5%) also were within 1 D of intended correction (Table 10). In the cases with surgical events, 12 eyes (92.3%) were within ⫾1.0 D of targeted spherical equivalent as compared to 14 eyes (77.8%) with postoperative flap repositioning (Table 10). We also examined the mean preoperative corneal power and diameter. Of the 950 complication-free eyes, the mean preoperative average keratometries were 44.25 ⫾1.82 with a mean corneal diameter of 11.61 ⫾ 1.44. We found that 18 of 19 keratome complications had steeper-than-average corneas averaging 45.7 D. Thin flaps and buttonholes had the steepest corneas averaging 45.9 D and 46.7 D, respectively. The one free cap had a very flat cornea averaging 40.94 D.

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The safety of LASIK in our series was excellent (Table 9) with 93.3% of eyes maintaining or gaining lines of BCVA after uncomplicated surgery. Even in cases in which microkeratome complications or other intraoperative events occurred, the BCVA is preserved with no loss of two or more lines. The group in which postoperative flap repositioning was required showed only a single eye with loss of two lines of vision. This is the case presented previously in which both eyes had loose epithelium and postoperative flap dislocation requiring suturing. The flaps are in good position in both eyes, but superficial punctate keratitis persists yet at 8

Figure 2. The mean time between the time the flap was turned and ablation was begun declined over the course of 1000 cases. Note that the range narrowed considerably as well.

Gimbel et al 䡠 Management of LASIK Complications Table 8. Reasons for Re-treatment in 950 Myopic LASIK Cases* (without Intraoperative or Perioperative Complications) (n ⫽ 290) Reason

n

%

Undercorrection Overcorrection Microwrinkles Epithelial ingrowth Regular astigmatism Monovision revised Shifted flap

230 28 11 10 6 3 2

79.31 9.66 3.79 3.45 2.07 1.03 0.69

* Of 950 cases without intraoperative or postoperative complications, follow-up of 1 to 22 months was available on 906 eyes (mean 3.8 months). Shifted flaps reported in the group occurred outside the initial 24-hour postoperative period.

Figure 3. Mean overall surgery time decreased, as did the range of overall surgery time, over the course of 1000 cases.

months postrepositioning. In addition, the majority of eyes were within ⫾1 D of targeted spherical equivalent at latest follow-up (Table 10). The safety and efficacy, as measured by the postoperative BCVA and spherical equivalent, compare favorably with results from a series of similar sized samples (Waring et al. Invest Ophthalmol Vis Sci 1997;38:S231). The microkeratome complication rate (1.9%) and postoperative Table 7. Re-treatment Rates for 1000 Myopic LASIK Cases*

Group Uncomplicated LASIK Microkeratome complications Intraoperative events Perioperative flap repositionings

n

No. of Eyes Needing Re-treatment

%

Mean Time to Re-treatment (mos)

950

290

30.5

5.1

19

2

10.5

7.5

13

3

23.0

8.0

18

6

33.3

3.7

* In the group with other intraoperative events recorded, 3 of 13 (23%) had retreatments with a mean time to re-treatment of 8 months; 2 of these were for undercorrection and 1 was for overcorrection; 6 of 18 (33.3%) cases that required postoperative flap repositioning underwent re-treatment with a mean time of 3.6 months; re-treatment was done for one case each of astigmatism, irregular astigmatism, interface debris, halos, undercorrection, and overcorrection. Reasons for re-treatment in patients without intraoperative or postoperative complications are summarized in Table 8.

flap complication rate (1.8%) in this series also compare favorably with that reported in a series of similar size (Stulting et al. Invest Ophthalmol Vis Sci 1997;38:S231). In a smaller series (34 –143 eyes), the rate of microkeratome complications is reported to be 0.7% to 10%.3–5 Although 13 (40.6%) of the 32 cases with recorded intraoperative complications and events had the LASIK procedure discontinued at the initial time of surgery, 9 (69.2%) of those 13 had LASIK performed successfully at a later date. The remaining cases either had no refractive surgery to date or another procedure as reported. This emphasizes that with proper management, not only can BCVA be preserved despite intraoperative complications, but also LASIK usually can be performed successfully at a later date. The surgeon should not be averse to delaying the completion of the surgery when appropriate. There has been frequent mention in the literature of the learning curve of LASIK with particular attention to the need of becoming familiar with the automated microkeratome.2– 4 The LASIK series reported in the literature to date either are comprised of much smaller numbers of cases or involve many surgeons. This series was of the first 1000 cases performed by a single surgeon and shows that the microkeratome-related intraoperative complication of incomplete pass rate does decline with the individual surgeon’s experience (Table 6, Fig 1). This learning curve also is reflected in the data regarding time between flap turning and ablation (Fig 2) and overall surgery time (Fig 3). Thus, not only did the rate of microkeratome complications decline, but the surgeon also became more efficient as reflected in the decrease in overall surgery time. At our center, associates who have begun LASIK at a later date have benefited from the sharing of accumulated knowledge and mentoring; one associate has had an intraoperative microkeratome complication rate of 4 (1.28%) in the first 312 cases as compared to 12 (3.84%) in the first 312 of this 1000-case series. This confirms that novice LASIK surgeons can benefit from the extended interaction with more experienced surgeons beyond what one learns at a course. In addition, although the rate of microkeratomerelated complications for the second surgeon (JAV) was lower compared with that of the original surgeon (HVG) for

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Ophthalmology Volume 105, Number 10, October 1998 Table 9. Postoperative Best-corrected Visual Acuity 6 Months Postoperation Comparing Microkeratome Complications, Surgical Events, Flap Repositioning, and Complication-free Cases Microkeratome Complications (n ⴝ 19)

Surgical Events (n ⴝ 13)

Flap Repositioning (n ⴝ 18)

No Complications (n ⴝ 906)*

0 6 9 4 0

0 3 8 2 0

0 5 9 3 1

7 42 796 45 16

Gain of 2 lines Gain of 1 line Same Loss of 1 line Loss of ⱖ 2 lines

* Mean follow-up ⫽ 3.8 months.

the first 312 operations performed, it was not as low as in the most recent 312 (HVG) surgeries, in which there was only a single microkeratome complication in cases 688 to 1000 in this series. The last eye had a steep cornea that resulted in a thin flap. Thus, not only is shared knowledge and mentoring helpful in hastening the learning process for the novice LASIK surgeon, but there is also a degree of individual experience that is integral or essential in becoming proficient with the techniques involved.

LASIK Technique: Avoiding Complications The learning curve that occurs as experience performing LASIK is gained can be modified by carefully recording details of every surgery and analyzing the problems or complications and then modifying techniques accordingly in a process of continuous improvement. In these first 1000 myopic LASIK cases, the majority of complications were the result of 1 or more of the following: failure to achieve adequate exposure, failure to achieve adequate suction, loose epithelium, wrinkles or debris under flap, flap shrinkage, or dislodged flap. Failure to achieve adequate exposure can result from a number of causes. Speculum design and draping techniques are important elements in obtaining exposure for the suction ring and for the full pass of the microkeratome. An inadequately open palpebral fissure, particularly in a deep orbit, can lead to difficulty placing the suction ring. Although failure to achieve adequate suction may be the result of inadequate exposure, it may also be the result of poor technique in not pressing firmly or symmetrically on the globe before the suction is turned on and allowing conjunctiva to block the suction port. In addition, inadequate IOP

rise during suction may be the result of conjunctival scarring from previous scleral buckling for retinal detachment. Even when the ring can be placed properly, there may be difficulty obtaining or maintaining adequate suction for the microkeratome pass. Manipulations of the speculum or ring may also dislodge the suction ring. The lack of adequate IOP may result in poor flaps or buttonholes. Inadequate exposure may also result in the eyelid, speculum, or the drape interfering with the forward movement of the microkeratome and result in an incomplete pass. Interestingly, 13 (68.4%) of 19 intraoperative microkeratomerelated complications involved the right eye. We have found that exposure is even more critical when performing LASIK on the right eye because of the location of the stopper on the side of the Chiron microkeratome head. When performing LASIK in the right eye, the stopper will be located superiorly and is more likely to catch on the upper lid, speculum, or drape. It is important to keep this in mind when assessing adequacy of exposure. In 87 of these first 1000 eyes, a lateral canthotomy was performed to achieve adequate exposure (Table 2). None of these eyes had a microkeratome complication. One eye did, however, have a dislodged flap in the first hour after surgery, probably because of the reduced activity of the orbicularis and poor blinking. Avoiding buttonholes, thin flaps, and free caps may mean appreciating the relationship between anatomy and microkeratome mechanics. Figures 4 and 5 are schematics of our theory as to why corneas with significant steepening may be prone to buttonholes or thin flaps. Our theory is that these complications occur as a result of excess tissue being compressed beyond applanation by the keratome foot plate, causing buckling of the cornea. The microkeratome makes

Table 10. Deviation from Targeted SE 6 Months Postoperation Comparing Microkeratome Complications, Surgical Events, Flap Repositioning, and Complication-free Cases

⫾0.50 ⫾1.00 ⫾2.00

Microkeratome Complications (n ⴝ 17)*

Surgical Events (n ⴝ 13)

Flap Repositionings (n ⴝ 18)

No Complications (n ⴝ 906)†

10 13 16

9 12 13

11 14 17

557 795 906

* Two canceled surgeries to be rescheduled. † Mean followup ⫽ 3.8 months.

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Gimbel et al 䡠 Management of LASIK Complications

Figure 4. A schematic showing applanation of normal and steep cornea by microkeratome. The steep cornea buckles under the microkeratome foot plate.

a complete pass with a normal size flap, but the central area is thinned or buttonholed. Even though these cases are categorized as microkeratome complications, we conclude that these are not related to learning curve or faulty technique but rather are related to the anatomy and mechanics. A different suction ring design and/or a foot plate to make a deeper cut is suggested for these steep corneas to avoid thin flaps and buttonholes. The free cap may also be an issue of anatomic and mechanical relationship and not related to learning the LASIK technique. Further microkeratome design modifications are required for the option of selecting the appropriate suction ring and depth plate for extremes in corneal curvature. Loose epithelium (especially on the superior aspect of the cornea) is a common finding in PRK and LASIK surgery. The overuse of preoperative anesthetic drops can soften the epithelium and contribute to epithelial adherence problems during surgery. As a rule, preoperative topical medications should be used sparingly. Despite precaution, stretched, torn, and wrinkled epithelia can result from the keratome pass. Two of the cases with epithelial bullae were managed successfully by carefully repositioning the epithelium and then protecting it with bandage contact lenses for 12 to 24 hours, resulting in no loss of BCVA. Flap wrinkles or debris under the flap may result from poor fluid management and from flap and epithelium problems. Too much irrigation may draw debris from the cul-de-sac into the interface. Prolonged or repeated irrigation under the flap can cause tissue swelling and retraction of the edges of the flap. Rather than irrigating under the whole flap for debris that is not central, we irrigate only under the edge where the debris is located. This minimizes flap and stromal hydration with the added risk of poor adherence. Excessive drying may result in flap shrinkage. Touching or stroking the flap with any more than a feather-light touch with a very wet sponge may stretch the flap and cause microwrinkles, adversely affecting the quality of vision. Proper management of the flap requires a very delicate touch. Intraoperatively dislodged flaps occurred in two cases when patients squeezed and the eye turned up as the speculum and drapes were removed. We now ask patients to look straight ahead and to not squeeze as the speculum is lifted

away from the globe, and we hold the eyelids open as the drape is removed. If the flap should become dislodged within the first hour after surgery while the patient is waiting in recovery, the repositioning is usually straightforward. There may be some wrinkles in the epithelium, but the flap wrinkles can usually be smoothed out during the repositioning. In one of our cases with previous orbital trauma and lagophthalmos, the flap became dislodged while the patient was waiting in the recovery room, probably because of drying from incomplete blinking. A lateral canthotomy was required. The flap was repositioned but dislodged again despite a bandage contact lens that was placed. The epithelium was so edematous at the time of the second repositioning that much of it abraded when the flap was repositioned. Because of this and swelling of the flap, the flap was sutured into position to avoid repeated shifting. Unfortunately, some epithelial ingrowth appeared at the temporal edge of the flap, requiring further surgery. The epithelial ingrowth was removed successfully, and the patient has recovered with 20/15 visual acuity 6 months after surgery. We learned from this case that a moisture chamber is mandatory until topical and regional anesthetic wear off and also when replacing edematous flaps. A forceps at the edge rather than touching the epithelium may avoid this epithelial abrasion. Since the introduction (April 1997) of routinely using a postoperative plastic shield moisture chamber for a few hours after surgery, the incidence of flap repositioning has decreased to 1 in the latest 600 cases. In the early postoperative period, 18 cases required flap repositioning within the first 24 hours after LASIK surgery. These repositionings were related to significant microwrinkles in the flap, poor adherence of the edge of the flap resulting in edge folds from eyelid pressure, or shifted flap due to dehydration, lid pressure, or other factors. Sixteen of the 18 repositionings were done within a few hours of surgery, whereas 2 flaps shifted after discharge and were only noted to be shifted at the first day postoperative visit. Two of the 12 shifted flaps required suturing after multiple attempts at repositioning. Lagophthalmos in one patient and lid retraction with a poor blink in another patient probably were responsible factors. We have learned over time that not only does surgery time and adherence affect flaps shifting, but so does relative humidity, blink reflex, exophthalmos,

Figure 5. A schematic showing applanation of normal and flat corneas by microkeratome. The flat cornea produces a free cap in with a small diameter.

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Ophthalmology Volume 105, Number 10, October 1998 lagophthalmos, extra irrigation, and lateral canthotomy in which the local anesthetic affects the orbicularis. With proper attention to these factors, we have noticed a significant decrease in the flap repositions by the 600th case. If the flap is dislodged for a longer period of time and not reported or noticed until the first postoperative appointment, the wrinkles in the flap stroma will not smooth out without using techniques to stretch them out. The tips of dry Merocel sponges can be used to manipulate the flap after it begins to adhere to the stromal bed. This technique can be used only if the epithelium is firmly adherent to the flap or if the epithelium is removed purposely for this maneuver. Alternatively, the flap edges can be sutured to stretch out the wrinkles. In all cases of repositioning, the epithelium must be removed carefully from the stromal bed and from the edges of the flap to avoid ingrowth and for adequate visualization to be able to precisely approximate the tissue. When there is a curled edge of the flap due to squeezing the eyelids or rubbing the eye and the gentian violet marks are still lined up (within the first half hour of the immediate postoperative period), the whole flap does not have to be lifted again. In the quadrant in which this occurs (it usually happens superiorly), the small area where there are wrinkles because the edge has been bunched up a little bit can be stretched back into position using the tip of a dry Merocel sponge. If this does not work or if the epithelium is loose, not allowing this procedure, then one has to refloat at least that section of the flap to get it back into position. If the flap dislocation is not noted or reported until the patient comes in the first day after surgery, a Paton spatula is used to clear epithelium from the very edge of the flap. Then the flap is lifted and the epithelium is removed from the stromal bed at the edges where the stromal bed has been exposed. There is usually epithelium growing over the exposed stroma. Any other epithelium at the edge of the stromal bed needs to be either wiped back or scraped off with the spatula. The reason for all this management of the epithelium is not only to prevent epithelial ingrowth but also so that one can see the edges to position the flap properly because the gentian violet marks are no longer there. In these situations, one can float the flap to make it supple and then verify the correct position by seeing the stromal edge of the flap properly approximated around the circumference of the flap. For visually significant central wrinkles without dislocation noted 24 hours or more after surgery, simply refloating the flap will not eliminate the wrinkles. In these cases, one must clear the edges again, refloat, and stretch out the flap with sutures that are left in place long enough for good flap stroma adhesion. For the individual surgeon, it is important to become facile in the handling of the microkeratome through practice in the wet laboratory. One of the difficulties often encountered by the beginning LASIK surgeon is getting the two components of the Chiron microkeratome to interact properly; some surgeons find that practicing the insertion of the microkeratome head into the suction ring with eyes closed is helpful in learning tactile clues that will augment visual clues. As in any surgical procedure, there are nuances to performing LASIK in a highly efficient and safe manner that can be appreciated only through observing an experienced

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surgeon and then gaining experience personally. It is helpful to run through the exact steps while observing and then mentally rehearse the entire procedure. Learning how to manage problems such as buttonhole, free cap, incomplete cuts, or failure of the flap to adhere is essential to the overall safety and satisfaction of LASIK patients. This is an area in which the novice surgeon can benefit greatly from observing an experienced surgeon. It also is beneficial to the surgeon during his or her learning curve to monitor the surgeon’s progress through detailed documentation of measurements, surgical steps, and events in a medical database and to record and review surgical video footage. The skills gained in the learning curve of myopic eyes have been transferred to our hyperopic LASIK learning curve. When hyperopic LASIK began in May 1996, the incidence of microkeratome complications was 2 (0.88%) in the first 226 eyes (HVG) compared to 11 (4.87%) complications in the first 226 myopic eyes (HVG). These two complications were free caps in flat corneas, average keratometry 39.9 D and 42.0 D. The anatomy of these two corneas probably accounts for the complication rather than the lack of skill on the part of the surgeon. What we have learned by analyzing our data on the first 1000 cases and supported by additional experience is that large, very steep corneas should be cut with a deeper than 160-␮m depth plate and that very flat corneas should be cut either with the Chiron Hansatome (Chiron Vision Corp., Irvine, CA) or a microkeratome with adjustable stop to be set for a larger hinge. Another alternative is to visually control the stop of the microkeratome. This is used routinely by some surgeons, but it takes practice and does, even after skills are developed, result in an occasional free cap. In conclusion, there is a consensus among the majority of surgeons performing LASIK that there is a definite learning curve to becoming proficient in this technique. This retrospective analysis of the first 1000 myopic LASIK cases performed by a single surgeon confirms this and further emphasizes the need for continual assessment and refinement of surgical techniques and skill transfer methods. There were no sight-threatening complications in this series, underscoring the fact that proper management of intraoperative and postoperative complications preserves BCVA. The most commonly encountered complications can generally be avoided if the following fundamental principles are kept in mind: attention to detail, quick surgery, delicate handling of tissues, consistent timing, and careful fluid use and management (Fig 5). The experience at our center shows that there is both an individual learning curve and a learning process that occurs between surgeons. Novice LASIK surgeons can benefit from more experienced surgeons through the sharing of accumulated knowledge and by taking advantage of mentoring opportunities.

References 1. Pallikaris IG, Papatzanaki ME, Stathi EZ, et al. Laser in situ keratomileusis. Lasers Surg Med 1990;10:463– 8.

Gimbel et al 䡠 Management of LASIK Complications 2. Gimbel HV, Basti S, Kaye GB, Ferensowicz M. Experience during the learning curve of laser in situ keratomileusis. J Cataract Refract Surg 1996;22:542–50. 3. Perez–Santonja JJ, Bellot J, Claramonte P, et al. Laser in situ keratomileusis to correct high myopia. J Cataract Refract Surg 1997;23:372– 85.

4. Marinho A, Pinto MC, Pinto R, et al. LASIK for high myopia: one year experience. Ophthalmic Surg Lasers 1996;27(5 Suppl):S517–20. 5. Fiander DC, Tayfour F. Excimer laser in situ keratomileusis in 124 myopic eyes. J Refract Surg 1995;11(3 Suppl): S234 – 8.

Discussion by Thomas E. Clinch, MD The initial emphasis with excimer laser surgery was on photorefractive keratectomy (PRK), which has been the subject of numerous clinical studies. The visual results and complications of PRK have been well established in the literature. This provides clinicians with a knowledge base to counsel and treat patients. Just as many surgeons were becoming comfortable with PRK, laser in situ keratomileusis (LASIK) rapidly emerged to become a more popular procedure. The appeal of rapid visual recovery, negligible discomfort, and substantially less postoperative care has made the procedure the overwhelming choice for many surgeons and patients. In most geographic regions, public perception is that LASIK has replaced an older, inferior procedure. Although there has been a stampede toward LASIK, a paucity of peer review literature exists to substantiate the safety and efficacy of the procedure.1–7 This comprehensive review by Gimbel is a welcome, and necessary, addition to the ophthalmic literature. It quantifies the effect of surgical experience on the rate of LASIK complications and provides insightful suggestions on how to reduce the risk of these problems. Because the report encompasses 1000 cases, it provides information on the incidence of complications by a novice, intermediate, and experienced LASIK surgeon. Despite extensive experience with anterior segment procedures, Gimbel reported a 9-fold higher complication rate in his first 200 cases when compared to his later cases. This supports the impression of other surgeons that the procedure has a definite learning curve.1,2 LASIK requires substantial training and education. All laser centers should establish stringent criteria to credential physicians as well as provide proctoring of initial cases. When mentored by an experienced surgeon, Gimbel’s associate had a 3-fold reduction in microkeratome complications in his first 312 cases. Although proctoring of these cases was quite important, greater staff experience with the assembly and care of the microkeratome may also have played a role. Because LASIK is a relatively new procedure, often both surgeon and staff undergo the microkeratome learning curve together. The lack of experience in caring for the microkeratome also may have contributed to the higher complication rate seen in Gimbel’s initial cases. When novice surgeons are assisted by a well-trained, knowledgeable staff, the rate of operative complications should continue to be reduced. As new microkeratomes are used by experienced surgeons, it also will be interesting to determine whether a higher incidence of complications occurs in their initial cases. Corneal topography was reported to be one of the parameters measured during the initial evaluation. Reporting on the postoperative topography was unfortunately beyond the scope of this comprehensive review. Decentration has been reported to occur more frequently with myopic LASIK procedures than with PRK procedures.3 Comparison of the centration in the initial 200 cases versus later cases would benefit our understanding of the surgeon

John Moran Eye Center, University of Utah, Salt Lake City, Utah. Address correspondence to Thomas E. Clinch, MD, John Moran Eye Center, 50 N. Medical Drive, Salt Lake City, UT 84132.

learning curve. Patients with flap complications such as thin flaps, flap shrinkage, and buttonholes are at a greater risk of visual dysfunction. Qualitative disturbances in day or night vision; reduced contrast sensitivity; and/or glare, halos, ghost images, or frank diplopia may occur. Analysis of the corneal topography of these patients might add further insight into how these complications affect the corneal surface. Patients with high levels of myopia are at risk of having corneal ectasia develop if there is an insufficient amount of undisturbed posterior cornea. In this study, myopia levels up to ⫺22.0 diopters were treated with a 160-␮m plate. Although the authors have most likely abandoned LASIK in high myopia, a future evaluation on the incidence of corneal ectasia in the 63 eyes with high myopia (ⱖ15 diopters) would be beneficial. In high myopia, corneal topography and pachymetry are essential to planning enhancement surgery for residual myopia. If residual myopia is caused by ectasia, further ablation will only exacerbate the situation. The rapid visual recovery with the LASIK procedure provides an opportunity to perform bilateral simultaneous surgery. In this study, 241 patients underwent bilateral surgery. A comparison of the incidence of intraoperative and perioperative complications between unilateral and bilateral cases would be beneficial. It also would be valuable to evaluate the risk of complications and ablation centration between the first and second eye treated during bilateral surgery. In our center, a number of microkeratome complications, especially incomplete passes, occurred during treatment of the second eye. Although I did not personally have this experience, it caused me to alter my technique for bilateral surgery. The Automated Corneal Shaper (ACS) unit appeared to be more prone to jamming in the second eye. Balanced saline solution may form crystals in the microkeratome gears or suction ring or both, or there may be excess fluid in the tract or motor shaft. When using the ACS, I now cut the flap in each eye before performing stromal ablation (flap, flap, zap, zap). The gears and suction plate are carefully cleaned between eyes, and the head is detached from the motor shaft to remove any fluid. Since adopting this technique, we have had no further episodes of incomplete passes during treatment of second eyes. Whereas the emphasis of this report was on the 50 patients in whom complications developed, the results of the remaining 950 patients deserve further discussion. A large percentage of these cases (290 [30%] of 950) required retreatment. The majority of these revisions (264 [28%] of 290) were because of an unintended residual refractive error. Gimbel reports an incidence of retreatment that is higher than that of many published studies.1,2,4 –7 Many of the patients (38%) had moderate or high myopia, which may partially account for the lack of precision of the primary LASIK procedure. The software installed in most laser systems is calibrated for PRK. This forces many surgeons, such as in this study, to undercorrect their initial cases until a personal nomogram can be calculated. With the rapid emergence of LASIK, it is critical for the laser manufacturers to expedite the creation of LASIK software.

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Ophthalmology Volume 105, Number 10, October 1998 Improvements in microkeratome technology will most likely decrease, but not eliminate, intraoperative complications. The technical suggestions in the LASIK technique: Avoiding Complications section provide excellent clinical pearls. Operative complications were more frequent in the right eye, and this is the dominant eye for most patients. Although attention to the superiorly located ACS gear tract and stopper is important when making the flap in the right eye, it is also critical to ensure that the suction port is not occluded by the redundant conjunctiva of the inferior fornix. With the PRK procedure, the role of the surgeon was often downplayed. This well-written, comprehensive study clearly shows that when discussing LASIK surgery, the greatest emphasis should be placed on the word surgery. References 1. Marinho A, Pinto MC, Pinto R, et al. LASIK for high myopia: one year experience. Ophthalmic Surg Lasers 1996;27(5 Suppl):S517–20.

2. Perez–Santonja JJ, Bellot J, Claramonte P, et al. Laser in situ keratomileusis to correct high myopia. J Cataract Refract Surg 1997;23:372– 85. 3. Mulhern MG, Foley–Nolan A, O’Keefe M, Condon PI. Topographical analysis of ablation centration after excimer laser photorefractive keratectomy and laser in situ keratomileusis for high myopia. J Cataract Refract Surg 1997;23:488 –94. 4. Condon PI, Mulhern M, Fulcher T, et al. Laser intrastromal keratomileusis for high myopia and myopic astigmatism. Br J Ophthalmol 1997;81:199 –206. 5. Gu¨ell JL, Muller A. Laser in situ keratomileusis (LASIK) for myopia from ⫺7 to ⫺18 diopters. J Refract Surg 1996;12: 222– 8. 6. Knorz MC, Liermann A, Seiberth V, et al. Laser in situ keratomileusis to correct myopia from ⫺6.00 to ⫺29.00 diopters. J Refract Surg 1996;12:575– 84. 7. Fiander DC, Tayfour F. Excimer laser in situ keratomileusis in 124 myopic eyes. J Refract Surg 1995;11(3 Suppl):S234 – 8.

Request for Proposals The Glaucoma Research Foundation (GRF) is a national nonprofit organization dedicated to protecting the sight of persons with glaucoma, with the ultimate goal of finding a cure. We are soliciting grant requests for pilot projects. These one-page requests are a precursor to a formal grant application, and they are forwarded on approval of our Scientific Advisory Committee. To be considered, all projects must meet one or more of the five GRF strategic research goals listed below: • • • • •

Protect and restore the optic nerve Accurately monitor glaucoma progression Find the genes responsible for the glaucomas Understand intraocular pressure system and develop better treatments Determine the risk factors for glaucoma damage

For a copy of our research grant guidelines and a grant request form, please call (415) 986-3162, or write to the attention of Mel Garrett, Research Manager, Glaucoma Research Foundation, 490 Post Street, Suite 830, San Francisco, CA 94102. You can also complete a grant request form on our website at http://www.glaucoma.org/research.html. Request forms must be received and approved before our grant application deadline, which is December 15, 1998.

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