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Laser in situ keratomileusis after intracorneal rings
Laser in situ keratomileusis after intracorneal rings Report of 5 cases Elizabeth A. Davis, MD, David R. Hardten, MD, Richard L. Lindstrom, MD ABSTRACT Purpose: To examine the results of laser in situ keratomileusis (LASIK) after removal of intracorneal ring (ICR) segments. Setting: Active refractive surgery practice. Methods: The effect of ICR (0.45 mm) placement, the rapidity of refractive recovery after explantation, and the results of subsequent LASIK were examined in 5 eyes. Results: Four eyes developed induced astigmatism after ICR implantation. In 2 of these eyes, retained astigmatism was evident by manifest refraction or corneal topography even after ICR explantation. In 1 eye, the ICR procedure was aborted because of an intraoperative complication. All 5 eyes had subsequent uneventful LASIK. Conclusions: Intracorneal rings can induce astigmatism that may be retained even after explantation. Careful wound manipulation may reduce the incidence of this complication. Laser in situ keratomileusis after ICR removal appears to be safe and effective. J Cataract Refract Surg 2000; 26:1733–1741 © 2000 ASCRS and ESCRS
T
he recent United States Food and Drug Administration (FDA) approval of Intacs should allow increased use of these intracorneal ring (ICR) segments for the treatment of low myopia. Intracorneal rings add to existing refractive procedures such as laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and radial keratotomy (RK) that can now be offered to patients. Intracorneal rings have several distinct advantages over other refractive procedures. Unlike LASIK and PRK, ICRs spare the visual axis. There is essentially no risk of central corneal haze or scarring. Furthermore, no tissue is removed from the cornea. Instead, 2 poly(methyl methacrylate) ring segments are Accepted for publication August 15, 2000. Reprint requests to David R. Hardten, MD, 710 East 24th Street, Suite 106, Minneapolis, Minnesota 55404, USA. © 2000 ASCRS and ESCRS Published by Elsevier Science Inc.
inserted into the peripheral stroma. No flap is created, eliminating potential complications such as aberrant flaps, flap displacement, diffuse lamellar keratitis, and epithelial ingrowth.1 KeraVision reports that a high percentage (53%) of Intacs patients achieve an uncorrected visual acuity (UCVA) of 20/16 at 12 months (FDA report of premarket approval cohort; G.O. Waring, MD, “One-Year Results of the ICRS from the Phase III Study for the Correction of Myopia,” presented at the annual meeting of the American Academy of Ophthalmology, New Orleans, Louisiana, USA, November 1998). Furthermore, ICRs allow many patients to return to myopia; the manifest refraction (MR) returns rapidly to the preoperative measurement in most patients once the ICR segments are removed. When the refraction has stabilized after explantation, patients can return to spectacles or 0886-3350/00/$–see front matter PII S0886-3350(00)00704-5
LASIK AFTER ICRS
contact lenses or have one of the other refractive procedures. At present, the FDA has approved the use of Intacs in eyes with ⱕ3.00 diopters (D) of myopia and ⱕ1.00 D of astigmatism only. Three segment thicknesses (0.25 mm, 0.30 mm, and 0.35 mm) are available for this range of refractive error. An expanded Phase III trial of 2 larger segments (0.40 mm and 0.45 mm) and 1 smaller segment (0.21 mm) is being conducted. If the trial is successful, KeraVision may receive FDA approval for correction of an expanded range of – 0.75 to –5.00 D of myopia. Laser in situ keratomileusis is currently the most frequently used surgical method to treat refractive errors. It has been used as a primary refractive procedure and as an enhancement procedure following previous LASIK, automated lamellar keratoplasty, RK, PRK, astigmatic keratotomy (AK), cataract surgery, and penetrating keratoplasty.2–7 With the addition of ICRs to the refractive surgery armamentarium, there is an interest in whether LASIK can be performed in an eye in which ICRs were implanted and subsequently removed. In this study, we examined the results of 1 eye in each of 5 patients who had LASIK following an ICR procedure. In 4 patients, ICRs were explanted because of unsatisfactory postoperative vision. In 1 eye of 1 patient, the ICR procedure was aborted because of an intraoperative complication. We examined the refractive effect of the ICR procedure, the rapidity of refractive recovery after explantation, and the results of subsequent LASIK.
Patients and Methods Intracorneal Ring Insertion A drop of an antibiotic agent and diclofenac sodium (Voltaren威) were instilled in the eye 30 minutes before surgery. A topical anesthetic drop was then administered. The eye was prepped with povidone–iodine on the lids (5%) and in the conjunctival cul-de-sac (2.5%). The lids and lashed were draped sterilely, and a lid speculum was placed. Additional topical anesthetic drops were instilled. An inked procedure marker was used to mark the incision site at 12 o’clock along the circumference of an 8.0 mm optical zone. Ultrasonic pachymetry was used to measure corneal thickness at this location. 1734
A 1.9 mm radial incision was fashioned with a diamond knife set at 68% of the corneal thickness. Blunt dissection was performed to create a small lamellar pocket at the depth of the incision on each side. An additional anesthetic drop was applied to the conjunctiva. A vacuum guide was then aligned and suction applied. A glide was placed in the incision and a blunttipped counterclockwise dissector rotated in the vacuum guide 210 degrees. This was repeated in the clockwise direction. After the vacuum was released, the appropriate-size ICR segments were inserted into the tunnels. Finally, the wound was closed with 1 or 2 interrupted 10-0 nylon sutures. A drop of diclofenac sodium and an antibiotic and steroid ointment were administered. A hard clear plastic shield was placed over the operative eye. Postoperative Regimen A drop of tobramycin and dexamethasone (TobraDex威) was administered to the eye 4 times a day for 1 week. The patient was seen frequently in the postoperative period to monitor progress. The sutures were removed at 3 to 4 weeks or sooner if they became loose or the patient had a high level of astigmatism. Enhancements An enhancement procedure was performed in 2 eyes for progressive astigmatism. This was done by reincising the original superior wound for a length of 2.0 mm at 68% of the corneal thickness to attempt to reverse cicatrization of the wound. Intracorneal Ring Explantation Intracorneal ring segments were removed by prepping and draping the patient as described. The original incision was reopened with a 15 degree diamond blade. The proximal end of the tunnel was bluntly opened with a Sinskey hook. Adhesions and fibrous tissue were dissected with the Sinskey hook for 360 degrees around the circumference of the superior end of the segment and within the positioning holes. The Sinskey hook was placed beneath 1 segment and rotated into the positioning hole. The segment was rotated out of the channel. This was repeated for the second segment. The wound was irrigated and closed with either stromal hydration or a 10-0 nylon suture. The postoperative regi-
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men was the same as that following the original insertion. Laser In Situ Keratomileusis Procedure Surgery was performed in a particle-free environment with patients under topical proparacaine anesthesia. Merocel威 sponges (Xomed) and powderless gloves were used to reduce interface debris. A Hansatome keratome (Bausch & Lomb Surgical) was used to construct a 180 m superiorly hinged flap. Adequate suction was confirmed by verifying intraocular pressure to be ⱖ65 mm Hg with a Barraquer tonometer. Balanced salt solution (BSS威) or Refresh威 Tears was then used to lubricate the cornea. After the flap was created, suction was broken and the keratome reversed out of the ring. The flap was lifted with a forceps or spatula. Ablation was performed with the VISX Star 193 nm excimer laser using a maximum optical zone of 6.0 mm. Hydration was monitored visually during the ablation and modified as needed by the surgeon. For astigmatic treatments, an elliptical ablation was performed with the optical zone along the minor axis of 4.5 to 6.0 mm. The flap and bed were irrigated with BSS, and the flap was repositioned. The gutter around the edge of the flap was dried with a Merocel sponge while the central epithelium was kept moist. The flap was allowed to adhere for 5 minutes before the lid speculum was removed. A hard clear plastic shield was placed over the operative eye. Ofloxacin (Ocuflox威) and fluorometholone (FML威) were used 4 times daily for 2 weeks postoperatively. One drop of Voltaren was given preoperatively and postoperatively. The antibiotic and steroid were continued for 2 weeks. Follow-up Examinations At all follow-up examinations, UCVA, best corrected visual acuity (BCVA), MR, keratometry measure-
ments, and corneal topography were obtained. A careful slitlamp examination was also performed.
Results In cases 1 to 4, the vision after placement of ICRs was unsatisfactory because of induced astigmatism. In case 5, the procedure was aborted because the dissection was too shallow to allow ICR placement (Tables 1 to 4). Case 1 This 21-year-old woman had 0.45 mm ICR implantation in the right eye. The preoperative MR was –5.25 ⫹0.25 ⫻ 128 with keratometry readings of 46.75 ⫻ 100 and 47.00 ⫻ 10. There were no intraoperative complications. Postoperatively, the patient remained undercorrected with induced astigmatism. She was bothered by halos, glare, and poor night vision. Twelve months postoperatively, she had ICR explantation. The refraction reverted toward preoperative measurements by 1 week after ICR removal, although some induced astigmatism remained. Eighteen months after explantation, the patient had LASIK. On the first postoperative day, the UCVA was 20/20; by day 10, the refraction was plano. Case 2 This 35-year-old man had 0.45 mm ICR implantation in the right eye. The preoperative MR was –5.00 ⫹0.25 ⫻ 15 with keratometry readings of 45.25 ⫻ 180 and 46.87 ⫻ 90. There were no intraoperative complications. Postoperatively, the patient had residual myopia and astigmatism. He complained of glare in the evenings. Twelve months after surgery, he had an enhancement procedure for the astigmatism, with placement of a relaxing incision in the wound. The refraction and UCVA improved initially but by 1 month had reverted
Table 1. Summary of cases.
Case
Age
Sex
Date of ICR
ICR Thickness (mm)
Date of Incisional Enhancement
Date of ICR Explantation
Date of LASIK
Date of LASIK Enhancement
1
21
F
2 /21/96
0.45
—
2/19/97
8/14/98
—
2
35
M
2 /21/96
0.45
2/18/97
5/6/97
12/15/97
—
3
32
F
3 /27/96
0.45
2/20/97
6/11/97
12/29/97
9 /26/99
4
36
F
5 /14/96
0.45
—
2/12/97
3/26/99
—
5
37
F
3 /27/96
—
—
—
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—
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Table 2. Measurements before and after ICR implantation. Preoperative
Day 1 Post-ICR
Day 7 Post-ICR
Case
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
UCVA
1
8 /400
20 /20
⫺5.25
46.75 ⫻ 100
20/32
20/20
⫺4.50
—
20/40
⫹0.25
47.00 ⫻ 100
10 /200 20 /20
45.25 ⫻ 180
⫹0.25
46.87 ⫻ 90
20/40
20/16
4
5
20 /400 20 /20
20 /400 20 /20
20 /300 20 /15
⫺5.50
44.62 ⫻ 180 45.37 ⫻ 90
⫺5.00
44.75 ⫻ 180
sphere
45.62 ⫻ 90
⫺3.00
45.87 ⫻ 175
⫹0.25
46.95 ⫻ 85
20/25
20/100
20/200
20/16
20/63
20/20
⫻20
K Values
⫺4.00
—
⫻85
⫺1.00
40.25 ⫻ 180
⫹0.75
41.00 ⫻ 90
20/25
20/16
⫻120
sphere
MR
⫹2.50
⫻85
⫺5.00 ⫻15
3
20/25
⫹3.00
⫻128 2
BCVA
⫺2.00
⫺2.00
41.50 ⫻ 170
⫹0.75
43.50 ⫻ 80
⫻150 ⫺2.50
40.37 ⫻ 180
⫹1.00
⫹1.75
43.50 ⫻ 90
⫻105
⫻93
⫺2.00
—
20/63
20/25
⫺3.50
36.62 ⫻ 100
⫹1.50
⫹2.00
38.75 ⫻ 10
⫻180
⫻10
⫺2.75
—
20/100
20/40
⫺2.75
45.50 ⫻ 178
⫹0.50
⫹0.50
46.25 ⫻ 88
⫻90
⫻165
—
20/80
20/12.5
UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity; MR ⫽ manifest refraction; K ⫽ keratometry
to preenhancement values (Figure 1). Because of fluctuating vision, poor night vision, glare, and halos, the patient had ICR explantation 15 months after implantation. The refraction reverted to preimplantation levels in 2 weeks, although the corneal topography showed persistent asymmetric astigmatism (Figure 2). Seven months after ICR explantation, the patient had LASIK. On the first postoperative day, the UCVA was 20/25; at 3 months, it was 20/20.
Case 3 This 32-year-old woman had 0.45 mm ICR implantation in the right eye. The preoperative MR was –5.50 sphere with keratometry readings of 44.62 ⫻ 180 and 45.37 ⫻ 90. The slitlamp examination was notable for fleck dystrophy, which was not considered a contraindication for the surgery. There were no intraoperative complications. Postoperatively, the patient remained undercorrected with induced astigmatism. Eleven
Figure 1. (Davis) Corneal topography of case 2 after placement of ICRs and a corneal relaxing incision.
Figure 2.
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(Davis) Corneal topography of case 2 after ICR removal shows persistent asymmetric astigmatism.
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Table 2. (cont) Month 3 Post-ICR UCVA 20/25
Month 6 Post-ICR
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
20/20
⫺1.00
40.75 ⫻ 175
20/25
20/16
⫺2.50
41.75 ⫻ 176
20/20
20/16
⫺1.00
41.00 ⫻ 180
⫹2.75
43.00 ⫻ 85
⫹3.25
43.75 ⫻ 86
⫹2.25
43.75 ⫻ 90
⫻90 20/25
20/16
⫻89
⫺1.75
41.25 ⫻ 180
⫹2.00
44.00 ⫻ 90
20/32
20/25
⫻105 20/50
—
20/32
⫺1.75
40.00 ⫻ 180
⫹2.75
43.25 ⫻ 90
20/60
20/20
20/16
42.00 ⫻ 180
⫹1.50
45.25 ⫻ 90
20/32
20/20
⫺2.25
41.25 ⫻ 15
⫹2.00
44.75 ⫻ 105
⫻95
⫺2.50
39.50 ⫻ 11
⫹3.75
43.00 ⫻ 101
—
—
—
—
—
—
—
—
—
—
—
—
⫻99
⫺3.75
37.12 ⫻ 176
⫹1.75
40.00 ⫻ 86
20/100
20/25
⫻130 20/160
⫻85
⫺2.00 ⫻95
⫻93 20/100
Year 1 Post-ICR
⫺3.25
40.50 ⫻ 25
⫹2.50
45.50 ⫻ 135
⫻120
⫺3.00
45.75 ⫻ 180
⫹0.25
46.50 ⫻ 90
20/200
20/20
⫺2.75
45.62 ⫻ 176
sphere
46.50 ⫻ 86
⫻10
Table 3. Postenhancement measurements in cases 2 and 3. Day 1
Day 7
Month 1
Case
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
2
20/25
20/16
Plano
41.00 ⫻ 10
20/32
20/20
⫺2.00
39.75 ⫻ 12
20/40
20/16
⫺2.25
41.25 ⫻ 10
⫹0.75
44.00 ⫻ 100
⫹2.00
44.00 ⫻ 102
⫹2.00
44.50 ⫻ 100
⫻105 3
20/32
20/20
⫻100
⫹0.75
38.25 ⫻ 5
⫹2.00
41.50 ⫻ 95
20/40
20/63
⫻100
⫻90
⫺1.00
40.50 ⫻ 15
⫹0.75
43.75 ⫻ 105
20/50
20/25
⫻125
⫺2.25
41.75 ⫻ 180
⫹1.25
43.75 ⫻ 90
⫻105
UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity; MR ⫽ manifest refraction; K ⫽ keratometry
months postoperatively, she had an enhancement procedure. The refraction and UCVA improved initially but by 1 month regressed to near the preenhancement levels. Because her quality of vision was borderline, the patient had ICR explantation 15 months after implantation. The refraction reverted toward preimplantation measurements in 1 week, but she retained some induced astigmatism. Six and a half months after ICR explantation, she had LASIK (Figure 3). Initially, the UCVA was 20/25 with a MR of –1.00 ⫹0.50 ⫻ 140. However, it subsequently regressed to an MR of –2.00 ⫹0.75 ⫻ 135 with a UCVA of 20/70. The patient had an enhancement procedure 21 months later without complication.
One month after the enhancement, the UCVA was 20/25 with an MR of ⫹0.50 ⫹0.25 ⫻ 180. Three months after, the UCVA was 20/20 with an MR of plano. Case 4 This 36-year-old woman had 0.45 mm ICR implantation in the left eye. The preoperative MR was –5.00 sphere with keratometry readings of 44.75 ⫻ 180 and 45.62 ⫻ 90. Surgery was uneventful. However, early in the postoperative period, the ring segments migrated superiorly. They were repositioned in the third week. Nevertheless, the patient remained undercor-
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Table 4. Measurements before and after ICR explantation in cases 1 to 4. Preexplantation
Day 1 Postexplantation
Day 7 Postexplantation
Case
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
1
20/20
20/16
⫺1.00
41.00 ⫻ 180
20/20
20/20
⫺1.00
42.50 ⫻ 10
20/200
20/25
⫺5.50
44.50 ⫻ 5
⫹2.25
43.75 ⫻ 90
⫹2.50
46.50 ⫻ 100
⫹1.50
48.00 ⫻ 95
⫻85 2
20/25
20/20
⫻105
⫺2.00
41.75 ⫻ 10
⫹1.75
45.00 ⫻ 100
20/40
20/20
⫻90 3
20/50
20/26
20/63
20/32
⫻95
⫺2.50
43.75 ⫻ 180
⫹1.50
46.25 ⫻ 90
20/160
20/20
⫺4.00
45.00 ⫻ 5
sphere
46.25 ⫻ 95
⫻90
⫺2.00
39.25 ⫻ 180
⫹2.25
42.50 ⫻ 90
20/25
20/20
⫻90 4
K Values
⫺2.00
42.50 ⫻ 180
⫹1.00
43.75 ⫻ 90
20/200
20/15
⫻90
⫺2.00
37.75 ⫻ 20
⫹1.75
44.25 ⫻ 110
20/100
20/30
⫻120
⫺5.25
44.00 ⫻ 180
⫹2.50
47.37 ⫻ 90
⫻100
⫺3.50
41.75 ⫻ 10
⫹3.50
46.50 ⫻ 100
20/200
20/32
⫺4.00
—
sphere
⫻108
UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity; MR ⫽ manifest refraction; K ⫽ keratometry
Figure 3. (Davis) Slitlamp photograph of case 3 following LASIK.
Figure 4. (Davis) Corneal topography of case 4 following ICR
Top arrow points to ICR scar and bottom arrow, to LASIK flap edge.
placement shows induced astigmatism.
rected and had induced astigmatism (Figure 4). Because her vision was unsatisfactory, she had ICR explantation 9 months postoperatively. The refraction reverted quickly toward preoperative measurements. Despite this, the corneal topography continued to show superior steepening (Figure 5). Eleven months after ICR explantation, the patient had LASIK. The corneal topography continued to show the same superior steepening. One month after LASIK, the UCVA was 20/30 with an MR of – 0.75 ⫹0.75 ⫻ 120.
Case 5 This 37-year-old woman had attempted ICR surgery in the left eye in March 1996. The preoperative MR was –3.00 ⫹0.25 ⫻ 20. Intraoperatively, the procedure was aborted because an anterior perforation of the cornea occurred during construction of the second channel. No ICR segments were placed. The patient recovered uneventfully, with essentially no change in the MR and no loss of BCVA. Eight months after attempted ICR placement, she had LASIK. On the first postoperative
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Table 4. (cont) Month 1 Postexplantation
Month 3 Postexplantation
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
20/200
20/16
⫺6.00
46.25 ⫻ 10
20/200
20/16
⫺6.00
46.50 ⫻ 180
⫹1.00
46.50 ⫻ 100
⫹2.00
47.00 ⫻ 90
⫻95 20/200
20/16
10/160
20/16
⫻95
⫺5.00
46.00 ⫻ 10
sphere
47.00 ⫻ 100
⫺5.50
44.75 ⫻ 15
⫹1.25
45.25 ⫻ 105
20/200
20/16
20/200
20/16
⫻100 20/20
20/25
⫺4.50
45.50 ⫻ 180
sphere
46.50 ⫻ 70
⫺5.50
44.75 ⫻ 180
⫹1.25
45.50 ⫻ 90
⫻105
⫺4.50
44.50 ⫻ 180
sphere
45.50 ⫻ 90
20/200
20/25
⫺4.75
45.50 ⫻ 180
sphere
46.25 ⫻ 90
UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity; MR ⫽ manifest refraction; K ⫽ keratometry
day, the UCVA was 20/15 with an MR of ⫹0.50 sphere. At 1 year, it was 20/20 with an MR of –1.00 ⫹0.50 ⫻ 6.
Discussion Intacs ICR segments are now available in the U.S. for use in refractive surgery. The Phase II clinical trials,
in which the patients presented here were enrolled, included patients with spherical equivalents of –1.00 to – 6.00 D and no more than 1.00 D of astigmatism. However, Intacs are currently approved by the FDA for treatment of only –1.00 to –3.00 D of myopia spherical equivalent with 1.00 D or less of astigmatism.
Table 5. Measurements before and after LASIK. Post-LASIK Pre-LASIK
Day 1
Last Follow-up
Case
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
1
20/200
20/16
⫺5.25
46.50 ⫻ 35
20/20
20/20
⫹0.50
40.87 ⫻ 44
20/20
⫹1.00
47.00 ⫻ 125
⫹0.25
41.62 ⫻ 134
(10 days)
⫹0.75
41.50 ⫻ 177
20/20
⫹0.50
42.00 ⫻ 87
(3 mo)
⫻95 2
20/300
20/20
UCVA
BCVA
MR
K Values
20/20
Plano
42.12 ⫻ 30 43.00 ⫻ 120
⫻168
⫺4.50
45.75 ⫻ 180
sphere
47.00 ⫻ 90
20/25
20/20
20/15
20/200
20/16
⫺5.50
44.75 ⫻ 180
⫹1.00
45.50 ⫻ 90
20/25
20/20
CF
20/20
20/200
20/20
—
20/70
20/20
⫺5.50
46.00 ⫻ 180
⫹0.75
47.00 ⫻ 90
20/50
20/30
⫹0.75
45.62 ⫻ 176
—
⫹0.50
sphere
46.50 ⫻ 86
20/15
20/15
—
⫻135 20/30
20/30
⫺0.75
—
⫹0.75
(1 mo)
⫻135
⫺2.75
⫺2.00 ⫹0.75
(20.5 mo)
⫻140
⫻40 5
⫻100
⫹0.50
⫻105 4
⫺1.00
—
⫹0.25
⫻141 3
Plano
⫻120
⫹0.50
43.00 ⫻ 180
20/20
sphere
43.50 ⫻ 90
(12 mo)
20/15
⫺1.00
44.50 ⫻ 12
⫹0.50
45.00 ⫻ 101
⫻6 UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity; MR ⫽ manifest refraction; K ⫽ keratometry; mo ⫽ month; CF ⫽ counting fingers
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LASIK AFTER ICRS
Figure 5. (Davis) Corneal topography of case 4 following ICR removal shows persistent superior steepening.
In this series, all patients who required explantation had myopia of –5.00 D or more and had ICR segments that are thicker than those currently approved by the FDA. Intracorneal rings were removed for undercorrection as well as induced astigmatism. Explantation was performed after 9 months (range 9 to 15 months) according to the study protocol. In addition to poor UCVA, these patients complained of poor quality of vision (halos, glare, fluctuations, decreased night vision). This finding is in keeping with the predictions of a mathematical model constructed by Patel and coauthors.8 The study concluded that ICRs cannot correct more than – 4.00 D of myopia without significantly increasing ocular spherical aberration, which in turn compromises the final visual outcome. It is yet to be determined whether patients who receive the larger segment thicknesses in the extended Phase III clinical trials will have more visual side effects. Although keratometry readings and MR reverted rapidly toward preoperative levels, 2 patients retained some astigmatism. Topographically evident astigmatism was also seen in 2 other patients. Data from KeraVision on 34 patients in Phase II and III clinical trials who had Intacs removed showed that 7% of these patients retained 0.50 to 1.00 D of astigmatism at 3 months (FDA report of premarket approval cohort). This retained astigmatism may be more frequent in eyes with high myopia and may depend on the duration for which the segments have been in situ. This phenomenon is most likely due to corneal distortion near the superior wound as a result of wound contracture. Much of this may be 1740
due to extensive wound manipulation during implantation or the use of a 10-0 nylon suture. This results in corneal steepening in this meridian and with-the-rule (WTR) astigmatism, as found in all 4 cases of ICR implantation. This was best demonstrated by the post-ICR topography in cases 2 and 4. Currently, minimal wound manipulation and 11-0 nylon closure are recommended to decrease the incidence of induced astigmatism. Astigmatism may also be induced by central migration of the ICRs along the horizontal corneal diameter. The segments thus lie closer to the center in one meridian than the other. Since the early trials, the frequency of induced astigmatism has decreased as a result of careful and minimal wound manipulation during surgery. Additionally, sutures, which can induce astigmatism if tight, are no longer thought to be necessary if the wound edges can be approximated by stromal hydration with BSS. If sutures are needed to close a gaping wound, 11-0 nylon sutures are recommended to minimize fibrosis and wound contracture. Dissection that creates a smaller channel may reduce central migration of the segments, limiting induced astigmatism on this basis. Other causes of induced astigmatism include decentration of the segments, wound placement too close to the limbus with subsequent fibrovascular ingrowth, and proliferation of epithelial cysts with wound gape and against-the-rule astigmatism. The typical ICR patient develops about 0.50 D of steepening in the meridian of the incision. Hence, the surgeon might plan wound placement based on any preoperative astigmatism. In patients with preoperative WTR astigmatism, this can be reduced approximately 0.50 D by placing the incision in a temporal location. Although enhancements to reduce astigmatism were attempted by reopening and lengthening the wound, this procedure had only a short-term effect. It is not known whether other refractive procedures such as AK within the circumference of the ICR segments would be effective for treating induced astigmatism. Some patients had good UCVA despite having very ametropic refractions. For example, cases 1 and 2 had a UCVA of 20/25 3 months after ICR insertion with refractions of –1.00 ⫹2.75 ⫻ 90 and –1.75 ⫹2.00 ⫻ 105, respectively. This might be attributed to a multifocal cornea, which could also account for the patient’s complaints of glare, halos, and poor night vision.
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All 5 patients had successful LASIK. There were no cases of intraoperative flap complications, epithelial ingrowth, haze, diffuse lamellar keratitis, or infection. No patient had a loss of BCVA. All but case 3 had a UCVA of 20/30 or better at the last follow-up (although duration of follow-up varied greatly). In case 3, the UCVA was good initially but then regressed. A LASIK enhancement procedure was subsequently performed. We were able to achieve good results without adjustments to our typical LASIK procedure. Although no definitive study has been conducted to determine when it is safe to perform LASIK after ICR removal, it is probably best to wait at least 6 months after explantation before performing LASIK. Asbell and coauthors9 describe a case in which the excimer laser was used to perform an enhancement after ICR explantation. In this case, PRK was performed rather than LASIK. An excellent result was achieved. In conclusion, we found that in some cases, ICRs can induce astigmatism that may be retained even after explantation. In the range of correction clinically approved for use in the U.S. and with careful handling of the wound, these complications may be less likely. Additionally, LASIK after ICR removal appears to be a safe and effective procedure when ICRs do not achieve the desired result.
References 1. Hardten DR, Lindstrom RL. Management of LASIK complications. Oper Tech Cataract Refract Surg 1998; 1:32–39 2. Hardten DR, Lindstrom RL. Surgical correction of re-
3.
4.
5.
6.
7.
8.
9.
fractive errors after penetrating keratoplasty. Int Ophthalmol Clin 1997; 37(1):1–35 Webber SK, Lawless MA, Sutton GI, Rogers CM. LASIK for post penetrating keratoplasty astigmatism and myopia. Br J Ophthalmol 1999; 83:1013–1018 Forseto AS, Francesconi CM, Nose´ RA, Nose´ W. Laser in situ keratomileusis to correct refractive errors after keratoplasty. J Cataract Refract Surg 1999; 25:479 – 485 Arenas E, Maglione A. Laser in situ keratomileusis for astigmatism and myopia after penetrating keratoplasty. J Refract Surg 1997; 13:27–32 Parisi A, Salchow DJ, Zirm ME, Stieldorf C. Laser in situ keratomileusis after automated lamellar keratoplasty and penetrating keratoplasty. J Cataract Refract Surg 1997; 23:1114 –1118 Gu¨ell JJ, Gris O, de Mueller A, Corcostegui B. LASIK for the correction of residual refractive errors from previous surgical procedures. Ophthalmic Surg Lasers 1999; 30: 341–349 Patel S, Marshall J, Fitzke FW III. Model for deriving the optical performance of the myopic eye corrected with an intracorneal ring. J Refract Surg 1995; 11:248 –252 ¨O ¨ , Odrich M. Photorefractive kerAsbell PA, Uc¸akhan O atectomy after intrastromal corneal ring segment explantation. Am J Ophthalmol 1999; 128:755–756
From Minnesota Eye Laser and Surgery Centers, Minneapolis (Davis, Hardten, Lindstrom), Regions Medical Center, St. Paul (Hardten), and the University of Minnesota, Minneapolis (Davis, Hardten, Lindstrom), Minnesota, USA. Drs. Davis, Hardten, and Lindstrom are paid instructors for VISX and Bausch & Lomb LASIK surgery courses and for KeraVision Intacs training courses.
J CATARACT REFRACT SURG—VOL 26, DECEMBER 2000
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T
he recent United States Food and Drug Administration (FDA) approval of Intacs should allow increased use of these intracorneal ring (ICR) segments for the treatment of low myopia. Intracorneal rings add to existing refractive procedures such as laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and radial keratotomy (RK) that can now be offered to patients. Intracorneal rings have several distinct advantages over other refractive procedures. Unlike LASIK and PRK, ICRs spare the visual axis. There is essentially no risk of central corneal haze or scarring. Furthermore, no tissue is removed from the cornea. Instead, 2 poly(methyl methacrylate) ring segments are Accepted for publication August 15, 2000. Reprint requests to David R. Hardten, MD, 710 East 24th Street, Suite 106, Minneapolis, Minnesota 55404, USA. © 2000 ASCRS and ESCRS Published by Elsevier Science Inc.
inserted into the peripheral stroma. No flap is created, eliminating potential complications such as aberrant flaps, flap displacement, diffuse lamellar keratitis, and epithelial ingrowth.1 KeraVision reports that a high percentage (53%) of Intacs patients achieve an uncorrected visual acuity (UCVA) of 20/16 at 12 months (FDA report of premarket approval cohort; G.O. Waring, MD, “One-Year Results of the ICRS from the Phase III Study for the Correction of Myopia,” presented at the annual meeting of the American Academy of Ophthalmology, New Orleans, Louisiana, USA, November 1998). Furthermore, ICRs allow many patients to return to myopia; the manifest refraction (MR) returns rapidly to the preoperative measurement in most patients once the ICR segments are removed. When the refraction has stabilized after explantation, patients can return to spectacles or 0886-3350/00/$–see front matter PII S0886-3350(00)00704-5
LASIK AFTER ICRS
contact lenses or have one of the other refractive procedures. At present, the FDA has approved the use of Intacs in eyes with ⱕ3.00 diopters (D) of myopia and ⱕ1.00 D of astigmatism only. Three segment thicknesses (0.25 mm, 0.30 mm, and 0.35 mm) are available for this range of refractive error. An expanded Phase III trial of 2 larger segments (0.40 mm and 0.45 mm) and 1 smaller segment (0.21 mm) is being conducted. If the trial is successful, KeraVision may receive FDA approval for correction of an expanded range of – 0.75 to –5.00 D of myopia. Laser in situ keratomileusis is currently the most frequently used surgical method to treat refractive errors. It has been used as a primary refractive procedure and as an enhancement procedure following previous LASIK, automated lamellar keratoplasty, RK, PRK, astigmatic keratotomy (AK), cataract surgery, and penetrating keratoplasty.2–7 With the addition of ICRs to the refractive surgery armamentarium, there is an interest in whether LASIK can be performed in an eye in which ICRs were implanted and subsequently removed. In this study, we examined the results of 1 eye in each of 5 patients who had LASIK following an ICR procedure. In 4 patients, ICRs were explanted because of unsatisfactory postoperative vision. In 1 eye of 1 patient, the ICR procedure was aborted because of an intraoperative complication. We examined the refractive effect of the ICR procedure, the rapidity of refractive recovery after explantation, and the results of subsequent LASIK.
Patients and Methods Intracorneal Ring Insertion A drop of an antibiotic agent and diclofenac sodium (Voltaren威) were instilled in the eye 30 minutes before surgery. A topical anesthetic drop was then administered. The eye was prepped with povidone–iodine on the lids (5%) and in the conjunctival cul-de-sac (2.5%). The lids and lashed were draped sterilely, and a lid speculum was placed. Additional topical anesthetic drops were instilled. An inked procedure marker was used to mark the incision site at 12 o’clock along the circumference of an 8.0 mm optical zone. Ultrasonic pachymetry was used to measure corneal thickness at this location. 1734
A 1.9 mm radial incision was fashioned with a diamond knife set at 68% of the corneal thickness. Blunt dissection was performed to create a small lamellar pocket at the depth of the incision on each side. An additional anesthetic drop was applied to the conjunctiva. A vacuum guide was then aligned and suction applied. A glide was placed in the incision and a blunttipped counterclockwise dissector rotated in the vacuum guide 210 degrees. This was repeated in the clockwise direction. After the vacuum was released, the appropriate-size ICR segments were inserted into the tunnels. Finally, the wound was closed with 1 or 2 interrupted 10-0 nylon sutures. A drop of diclofenac sodium and an antibiotic and steroid ointment were administered. A hard clear plastic shield was placed over the operative eye. Postoperative Regimen A drop of tobramycin and dexamethasone (TobraDex威) was administered to the eye 4 times a day for 1 week. The patient was seen frequently in the postoperative period to monitor progress. The sutures were removed at 3 to 4 weeks or sooner if they became loose or the patient had a high level of astigmatism. Enhancements An enhancement procedure was performed in 2 eyes for progressive astigmatism. This was done by reincising the original superior wound for a length of 2.0 mm at 68% of the corneal thickness to attempt to reverse cicatrization of the wound. Intracorneal Ring Explantation Intracorneal ring segments were removed by prepping and draping the patient as described. The original incision was reopened with a 15 degree diamond blade. The proximal end of the tunnel was bluntly opened with a Sinskey hook. Adhesions and fibrous tissue were dissected with the Sinskey hook for 360 degrees around the circumference of the superior end of the segment and within the positioning holes. The Sinskey hook was placed beneath 1 segment and rotated into the positioning hole. The segment was rotated out of the channel. This was repeated for the second segment. The wound was irrigated and closed with either stromal hydration or a 10-0 nylon suture. The postoperative regi-
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men was the same as that following the original insertion. Laser In Situ Keratomileusis Procedure Surgery was performed in a particle-free environment with patients under topical proparacaine anesthesia. Merocel威 sponges (Xomed) and powderless gloves were used to reduce interface debris. A Hansatome keratome (Bausch & Lomb Surgical) was used to construct a 180 m superiorly hinged flap. Adequate suction was confirmed by verifying intraocular pressure to be ⱖ65 mm Hg with a Barraquer tonometer. Balanced salt solution (BSS威) or Refresh威 Tears was then used to lubricate the cornea. After the flap was created, suction was broken and the keratome reversed out of the ring. The flap was lifted with a forceps or spatula. Ablation was performed with the VISX Star 193 nm excimer laser using a maximum optical zone of 6.0 mm. Hydration was monitored visually during the ablation and modified as needed by the surgeon. For astigmatic treatments, an elliptical ablation was performed with the optical zone along the minor axis of 4.5 to 6.0 mm. The flap and bed were irrigated with BSS, and the flap was repositioned. The gutter around the edge of the flap was dried with a Merocel sponge while the central epithelium was kept moist. The flap was allowed to adhere for 5 minutes before the lid speculum was removed. A hard clear plastic shield was placed over the operative eye. Ofloxacin (Ocuflox威) and fluorometholone (FML威) were used 4 times daily for 2 weeks postoperatively. One drop of Voltaren was given preoperatively and postoperatively. The antibiotic and steroid were continued for 2 weeks. Follow-up Examinations At all follow-up examinations, UCVA, best corrected visual acuity (BCVA), MR, keratometry measure-
ments, and corneal topography were obtained. A careful slitlamp examination was also performed.
Results In cases 1 to 4, the vision after placement of ICRs was unsatisfactory because of induced astigmatism. In case 5, the procedure was aborted because the dissection was too shallow to allow ICR placement (Tables 1 to 4). Case 1 This 21-year-old woman had 0.45 mm ICR implantation in the right eye. The preoperative MR was –5.25 ⫹0.25 ⫻ 128 with keratometry readings of 46.75 ⫻ 100 and 47.00 ⫻ 10. There were no intraoperative complications. Postoperatively, the patient remained undercorrected with induced astigmatism. She was bothered by halos, glare, and poor night vision. Twelve months postoperatively, she had ICR explantation. The refraction reverted toward preoperative measurements by 1 week after ICR removal, although some induced astigmatism remained. Eighteen months after explantation, the patient had LASIK. On the first postoperative day, the UCVA was 20/20; by day 10, the refraction was plano. Case 2 This 35-year-old man had 0.45 mm ICR implantation in the right eye. The preoperative MR was –5.00 ⫹0.25 ⫻ 15 with keratometry readings of 45.25 ⫻ 180 and 46.87 ⫻ 90. There were no intraoperative complications. Postoperatively, the patient had residual myopia and astigmatism. He complained of glare in the evenings. Twelve months after surgery, he had an enhancement procedure for the astigmatism, with placement of a relaxing incision in the wound. The refraction and UCVA improved initially but by 1 month had reverted
Table 1. Summary of cases.
Case
Age
Sex
Date of ICR
ICR Thickness (mm)
Date of Incisional Enhancement
Date of ICR Explantation
Date of LASIK
Date of LASIK Enhancement
1
21
F
2 /21/96
0.45
—
2/19/97
8/14/98
—
2
35
M
2 /21/96
0.45
2/18/97
5/6/97
12/15/97
—
3
32
F
3 /27/96
0.45
2/20/97
6/11/97
12/29/97
9 /26/99
4
36
F
5 /14/96
0.45
—
2/12/97
3/26/99
—
5
37
F
3 /27/96
—
—
—
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11/6/96
—
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Table 2. Measurements before and after ICR implantation. Preoperative
Day 1 Post-ICR
Day 7 Post-ICR
Case
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
UCVA
1
8 /400
20 /20
⫺5.25
46.75 ⫻ 100
20/32
20/20
⫺4.50
—
20/40
⫹0.25
47.00 ⫻ 100
10 /200 20 /20
45.25 ⫻ 180
⫹0.25
46.87 ⫻ 90
20/40
20/16
4
5
20 /400 20 /20
20 /400 20 /20
20 /300 20 /15
⫺5.50
44.62 ⫻ 180 45.37 ⫻ 90
⫺5.00
44.75 ⫻ 180
sphere
45.62 ⫻ 90
⫺3.00
45.87 ⫻ 175
⫹0.25
46.95 ⫻ 85
20/25
20/100
20/200
20/16
20/63
20/20
⫻20
K Values
⫺4.00
—
⫻85
⫺1.00
40.25 ⫻ 180
⫹0.75
41.00 ⫻ 90
20/25
20/16
⫻120
sphere
MR
⫹2.50
⫻85
⫺5.00 ⫻15
3
20/25
⫹3.00
⫻128 2
BCVA
⫺2.00
⫺2.00
41.50 ⫻ 170
⫹0.75
43.50 ⫻ 80
⫻150 ⫺2.50
40.37 ⫻ 180
⫹1.00
⫹1.75
43.50 ⫻ 90
⫻105
⫻93
⫺2.00
—
20/63
20/25
⫺3.50
36.62 ⫻ 100
⫹1.50
⫹2.00
38.75 ⫻ 10
⫻180
⫻10
⫺2.75
—
20/100
20/40
⫺2.75
45.50 ⫻ 178
⫹0.50
⫹0.50
46.25 ⫻ 88
⫻90
⫻165
—
20/80
20/12.5
UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity; MR ⫽ manifest refraction; K ⫽ keratometry
to preenhancement values (Figure 1). Because of fluctuating vision, poor night vision, glare, and halos, the patient had ICR explantation 15 months after implantation. The refraction reverted to preimplantation levels in 2 weeks, although the corneal topography showed persistent asymmetric astigmatism (Figure 2). Seven months after ICR explantation, the patient had LASIK. On the first postoperative day, the UCVA was 20/25; at 3 months, it was 20/20.
Case 3 This 32-year-old woman had 0.45 mm ICR implantation in the right eye. The preoperative MR was –5.50 sphere with keratometry readings of 44.62 ⫻ 180 and 45.37 ⫻ 90. The slitlamp examination was notable for fleck dystrophy, which was not considered a contraindication for the surgery. There were no intraoperative complications. Postoperatively, the patient remained undercorrected with induced astigmatism. Eleven
Figure 1. (Davis) Corneal topography of case 2 after placement of ICRs and a corneal relaxing incision.
Figure 2.
1736
(Davis) Corneal topography of case 2 after ICR removal shows persistent asymmetric astigmatism.
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Table 2. (cont) Month 3 Post-ICR UCVA 20/25
Month 6 Post-ICR
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
20/20
⫺1.00
40.75 ⫻ 175
20/25
20/16
⫺2.50
41.75 ⫻ 176
20/20
20/16
⫺1.00
41.00 ⫻ 180
⫹2.75
43.00 ⫻ 85
⫹3.25
43.75 ⫻ 86
⫹2.25
43.75 ⫻ 90
⫻90 20/25
20/16
⫻89
⫺1.75
41.25 ⫻ 180
⫹2.00
44.00 ⫻ 90
20/32
20/25
⫻105 20/50
—
20/32
⫺1.75
40.00 ⫻ 180
⫹2.75
43.25 ⫻ 90
20/60
20/20
20/16
42.00 ⫻ 180
⫹1.50
45.25 ⫻ 90
20/32
20/20
⫺2.25
41.25 ⫻ 15
⫹2.00
44.75 ⫻ 105
⫻95
⫺2.50
39.50 ⫻ 11
⫹3.75
43.00 ⫻ 101
—
—
—
—
—
—
—
—
—
—
—
—
⫻99
⫺3.75
37.12 ⫻ 176
⫹1.75
40.00 ⫻ 86
20/100
20/25
⫻130 20/160
⫻85
⫺2.00 ⫻95
⫻93 20/100
Year 1 Post-ICR
⫺3.25
40.50 ⫻ 25
⫹2.50
45.50 ⫻ 135
⫻120
⫺3.00
45.75 ⫻ 180
⫹0.25
46.50 ⫻ 90
20/200
20/20
⫺2.75
45.62 ⫻ 176
sphere
46.50 ⫻ 86
⫻10
Table 3. Postenhancement measurements in cases 2 and 3. Day 1
Day 7
Month 1
Case
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
2
20/25
20/16
Plano
41.00 ⫻ 10
20/32
20/20
⫺2.00
39.75 ⫻ 12
20/40
20/16
⫺2.25
41.25 ⫻ 10
⫹0.75
44.00 ⫻ 100
⫹2.00
44.00 ⫻ 102
⫹2.00
44.50 ⫻ 100
⫻105 3
20/32
20/20
⫻100
⫹0.75
38.25 ⫻ 5
⫹2.00
41.50 ⫻ 95
20/40
20/63
⫻100
⫻90
⫺1.00
40.50 ⫻ 15
⫹0.75
43.75 ⫻ 105
20/50
20/25
⫻125
⫺2.25
41.75 ⫻ 180
⫹1.25
43.75 ⫻ 90
⫻105
UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity; MR ⫽ manifest refraction; K ⫽ keratometry
months postoperatively, she had an enhancement procedure. The refraction and UCVA improved initially but by 1 month regressed to near the preenhancement levels. Because her quality of vision was borderline, the patient had ICR explantation 15 months after implantation. The refraction reverted toward preimplantation measurements in 1 week, but she retained some induced astigmatism. Six and a half months after ICR explantation, she had LASIK (Figure 3). Initially, the UCVA was 20/25 with a MR of –1.00 ⫹0.50 ⫻ 140. However, it subsequently regressed to an MR of –2.00 ⫹0.75 ⫻ 135 with a UCVA of 20/70. The patient had an enhancement procedure 21 months later without complication.
One month after the enhancement, the UCVA was 20/25 with an MR of ⫹0.50 ⫹0.25 ⫻ 180. Three months after, the UCVA was 20/20 with an MR of plano. Case 4 This 36-year-old woman had 0.45 mm ICR implantation in the left eye. The preoperative MR was –5.00 sphere with keratometry readings of 44.75 ⫻ 180 and 45.62 ⫻ 90. Surgery was uneventful. However, early in the postoperative period, the ring segments migrated superiorly. They were repositioned in the third week. Nevertheless, the patient remained undercor-
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LASIK AFTER ICRS
Table 4. Measurements before and after ICR explantation in cases 1 to 4. Preexplantation
Day 1 Postexplantation
Day 7 Postexplantation
Case
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
1
20/20
20/16
⫺1.00
41.00 ⫻ 180
20/20
20/20
⫺1.00
42.50 ⫻ 10
20/200
20/25
⫺5.50
44.50 ⫻ 5
⫹2.25
43.75 ⫻ 90
⫹2.50
46.50 ⫻ 100
⫹1.50
48.00 ⫻ 95
⫻85 2
20/25
20/20
⫻105
⫺2.00
41.75 ⫻ 10
⫹1.75
45.00 ⫻ 100
20/40
20/20
⫻90 3
20/50
20/26
20/63
20/32
⫻95
⫺2.50
43.75 ⫻ 180
⫹1.50
46.25 ⫻ 90
20/160
20/20
⫺4.00
45.00 ⫻ 5
sphere
46.25 ⫻ 95
⫻90
⫺2.00
39.25 ⫻ 180
⫹2.25
42.50 ⫻ 90
20/25
20/20
⫻90 4
K Values
⫺2.00
42.50 ⫻ 180
⫹1.00
43.75 ⫻ 90
20/200
20/15
⫻90
⫺2.00
37.75 ⫻ 20
⫹1.75
44.25 ⫻ 110
20/100
20/30
⫻120
⫺5.25
44.00 ⫻ 180
⫹2.50
47.37 ⫻ 90
⫻100
⫺3.50
41.75 ⫻ 10
⫹3.50
46.50 ⫻ 100
20/200
20/32
⫺4.00
—
sphere
⫻108
UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity; MR ⫽ manifest refraction; K ⫽ keratometry
Figure 3. (Davis) Slitlamp photograph of case 3 following LASIK.
Figure 4. (Davis) Corneal topography of case 4 following ICR
Top arrow points to ICR scar and bottom arrow, to LASIK flap edge.
placement shows induced astigmatism.
rected and had induced astigmatism (Figure 4). Because her vision was unsatisfactory, she had ICR explantation 9 months postoperatively. The refraction reverted quickly toward preoperative measurements. Despite this, the corneal topography continued to show superior steepening (Figure 5). Eleven months after ICR explantation, the patient had LASIK. The corneal topography continued to show the same superior steepening. One month after LASIK, the UCVA was 20/30 with an MR of – 0.75 ⫹0.75 ⫻ 120.
Case 5 This 37-year-old woman had attempted ICR surgery in the left eye in March 1996. The preoperative MR was –3.00 ⫹0.25 ⫻ 20. Intraoperatively, the procedure was aborted because an anterior perforation of the cornea occurred during construction of the second channel. No ICR segments were placed. The patient recovered uneventfully, with essentially no change in the MR and no loss of BCVA. Eight months after attempted ICR placement, she had LASIK. On the first postoperative
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Table 4. (cont) Month 1 Postexplantation
Month 3 Postexplantation
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
20/200
20/16
⫺6.00
46.25 ⫻ 10
20/200
20/16
⫺6.00
46.50 ⫻ 180
⫹1.00
46.50 ⫻ 100
⫹2.00
47.00 ⫻ 90
⫻95 20/200
20/16
10/160
20/16
⫻95
⫺5.00
46.00 ⫻ 10
sphere
47.00 ⫻ 100
⫺5.50
44.75 ⫻ 15
⫹1.25
45.25 ⫻ 105
20/200
20/16
20/200
20/16
⫻100 20/20
20/25
⫺4.50
45.50 ⫻ 180
sphere
46.50 ⫻ 70
⫺5.50
44.75 ⫻ 180
⫹1.25
45.50 ⫻ 90
⫻105
⫺4.50
44.50 ⫻ 180
sphere
45.50 ⫻ 90
20/200
20/25
⫺4.75
45.50 ⫻ 180
sphere
46.25 ⫻ 90
UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity; MR ⫽ manifest refraction; K ⫽ keratometry
day, the UCVA was 20/15 with an MR of ⫹0.50 sphere. At 1 year, it was 20/20 with an MR of –1.00 ⫹0.50 ⫻ 6.
Discussion Intacs ICR segments are now available in the U.S. for use in refractive surgery. The Phase II clinical trials,
in which the patients presented here were enrolled, included patients with spherical equivalents of –1.00 to – 6.00 D and no more than 1.00 D of astigmatism. However, Intacs are currently approved by the FDA for treatment of only –1.00 to –3.00 D of myopia spherical equivalent with 1.00 D or less of astigmatism.
Table 5. Measurements before and after LASIK. Post-LASIK Pre-LASIK
Day 1
Last Follow-up
Case
UCVA
BCVA
MR
K Values
UCVA
BCVA
MR
K Values
1
20/200
20/16
⫺5.25
46.50 ⫻ 35
20/20
20/20
⫹0.50
40.87 ⫻ 44
20/20
⫹1.00
47.00 ⫻ 125
⫹0.25
41.62 ⫻ 134
(10 days)
⫹0.75
41.50 ⫻ 177
20/20
⫹0.50
42.00 ⫻ 87
(3 mo)
⫻95 2
20/300
20/20
UCVA
BCVA
MR
K Values
20/20
Plano
42.12 ⫻ 30 43.00 ⫻ 120
⫻168
⫺4.50
45.75 ⫻ 180
sphere
47.00 ⫻ 90
20/25
20/20
20/15
20/200
20/16
⫺5.50
44.75 ⫻ 180
⫹1.00
45.50 ⫻ 90
20/25
20/20
CF
20/20
20/200
20/20
—
20/70
20/20
⫺5.50
46.00 ⫻ 180
⫹0.75
47.00 ⫻ 90
20/50
20/30
⫹0.75
45.62 ⫻ 176
—
⫹0.50
sphere
46.50 ⫻ 86
20/15
20/15
—
⫻135 20/30
20/30
⫺0.75
—
⫹0.75
(1 mo)
⫻135
⫺2.75
⫺2.00 ⫹0.75
(20.5 mo)
⫻140
⫻40 5
⫻100
⫹0.50
⫻105 4
⫺1.00
—
⫹0.25
⫻141 3
Plano
⫻120
⫹0.50
43.00 ⫻ 180
20/20
sphere
43.50 ⫻ 90
(12 mo)
20/15
⫺1.00
44.50 ⫻ 12
⫹0.50
45.00 ⫻ 101
⫻6 UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity; MR ⫽ manifest refraction; K ⫽ keratometry; mo ⫽ month; CF ⫽ counting fingers
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LASIK AFTER ICRS
Figure 5. (Davis) Corneal topography of case 4 following ICR removal shows persistent superior steepening.
In this series, all patients who required explantation had myopia of –5.00 D or more and had ICR segments that are thicker than those currently approved by the FDA. Intracorneal rings were removed for undercorrection as well as induced astigmatism. Explantation was performed after 9 months (range 9 to 15 months) according to the study protocol. In addition to poor UCVA, these patients complained of poor quality of vision (halos, glare, fluctuations, decreased night vision). This finding is in keeping with the predictions of a mathematical model constructed by Patel and coauthors.8 The study concluded that ICRs cannot correct more than – 4.00 D of myopia without significantly increasing ocular spherical aberration, which in turn compromises the final visual outcome. It is yet to be determined whether patients who receive the larger segment thicknesses in the extended Phase III clinical trials will have more visual side effects. Although keratometry readings and MR reverted rapidly toward preoperative levels, 2 patients retained some astigmatism. Topographically evident astigmatism was also seen in 2 other patients. Data from KeraVision on 34 patients in Phase II and III clinical trials who had Intacs removed showed that 7% of these patients retained 0.50 to 1.00 D of astigmatism at 3 months (FDA report of premarket approval cohort). This retained astigmatism may be more frequent in eyes with high myopia and may depend on the duration for which the segments have been in situ. This phenomenon is most likely due to corneal distortion near the superior wound as a result of wound contracture. Much of this may be 1740
due to extensive wound manipulation during implantation or the use of a 10-0 nylon suture. This results in corneal steepening in this meridian and with-the-rule (WTR) astigmatism, as found in all 4 cases of ICR implantation. This was best demonstrated by the post-ICR topography in cases 2 and 4. Currently, minimal wound manipulation and 11-0 nylon closure are recommended to decrease the incidence of induced astigmatism. Astigmatism may also be induced by central migration of the ICRs along the horizontal corneal diameter. The segments thus lie closer to the center in one meridian than the other. Since the early trials, the frequency of induced astigmatism has decreased as a result of careful and minimal wound manipulation during surgery. Additionally, sutures, which can induce astigmatism if tight, are no longer thought to be necessary if the wound edges can be approximated by stromal hydration with BSS. If sutures are needed to close a gaping wound, 11-0 nylon sutures are recommended to minimize fibrosis and wound contracture. Dissection that creates a smaller channel may reduce central migration of the segments, limiting induced astigmatism on this basis. Other causes of induced astigmatism include decentration of the segments, wound placement too close to the limbus with subsequent fibrovascular ingrowth, and proliferation of epithelial cysts with wound gape and against-the-rule astigmatism. The typical ICR patient develops about 0.50 D of steepening in the meridian of the incision. Hence, the surgeon might plan wound placement based on any preoperative astigmatism. In patients with preoperative WTR astigmatism, this can be reduced approximately 0.50 D by placing the incision in a temporal location. Although enhancements to reduce astigmatism were attempted by reopening and lengthening the wound, this procedure had only a short-term effect. It is not known whether other refractive procedures such as AK within the circumference of the ICR segments would be effective for treating induced astigmatism. Some patients had good UCVA despite having very ametropic refractions. For example, cases 1 and 2 had a UCVA of 20/25 3 months after ICR insertion with refractions of –1.00 ⫹2.75 ⫻ 90 and –1.75 ⫹2.00 ⫻ 105, respectively. This might be attributed to a multifocal cornea, which could also account for the patient’s complaints of glare, halos, and poor night vision.
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LASIK AFTER ICRS
All 5 patients had successful LASIK. There were no cases of intraoperative flap complications, epithelial ingrowth, haze, diffuse lamellar keratitis, or infection. No patient had a loss of BCVA. All but case 3 had a UCVA of 20/30 or better at the last follow-up (although duration of follow-up varied greatly). In case 3, the UCVA was good initially but then regressed. A LASIK enhancement procedure was subsequently performed. We were able to achieve good results without adjustments to our typical LASIK procedure. Although no definitive study has been conducted to determine when it is safe to perform LASIK after ICR removal, it is probably best to wait at least 6 months after explantation before performing LASIK. Asbell and coauthors9 describe a case in which the excimer laser was used to perform an enhancement after ICR explantation. In this case, PRK was performed rather than LASIK. An excellent result was achieved. In conclusion, we found that in some cases, ICRs can induce astigmatism that may be retained even after explantation. In the range of correction clinically approved for use in the U.S. and with careful handling of the wound, these complications may be less likely. Additionally, LASIK after ICR removal appears to be a safe and effective procedure when ICRs do not achieve the desired result.
References 1. Hardten DR, Lindstrom RL. Management of LASIK complications. Oper Tech Cataract Refract Surg 1998; 1:32–39 2. Hardten DR, Lindstrom RL. Surgical correction of re-
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fractive errors after penetrating keratoplasty. Int Ophthalmol Clin 1997; 37(1):1–35 Webber SK, Lawless MA, Sutton GI, Rogers CM. LASIK for post penetrating keratoplasty astigmatism and myopia. Br J Ophthalmol 1999; 83:1013–1018 Forseto AS, Francesconi CM, Nose´ RA, Nose´ W. Laser in situ keratomileusis to correct refractive errors after keratoplasty. J Cataract Refract Surg 1999; 25:479 – 485 Arenas E, Maglione A. Laser in situ keratomileusis for astigmatism and myopia after penetrating keratoplasty. J Refract Surg 1997; 13:27–32 Parisi A, Salchow DJ, Zirm ME, Stieldorf C. Laser in situ keratomileusis after automated lamellar keratoplasty and penetrating keratoplasty. J Cataract Refract Surg 1997; 23:1114 –1118 Gu¨ell JJ, Gris O, de Mueller A, Corcostegui B. LASIK for the correction of residual refractive errors from previous surgical procedures. Ophthalmic Surg Lasers 1999; 30: 341–349 Patel S, Marshall J, Fitzke FW III. Model for deriving the optical performance of the myopic eye corrected with an intracorneal ring. J Refract Surg 1995; 11:248 –252 ¨O ¨ , Odrich M. Photorefractive kerAsbell PA, Uc¸akhan O atectomy after intrastromal corneal ring segment explantation. Am J Ophthalmol 1999; 128:755–756
From Minnesota Eye Laser and Surgery Centers, Minneapolis (Davis, Hardten, Lindstrom), Regions Medical Center, St. Paul (Hardten), and the University of Minnesota, Minneapolis (Davis, Hardten, Lindstrom), Minnesota, USA. Drs. Davis, Hardten, and Lindstrom are paid instructors for VISX and Bausch & Lomb LASIK surgery courses and for KeraVision Intacs training courses.
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