Mitomycin-C assisted photorefractive keratectomy in the treatment of buttonholed laser in situ keratomileusis flaps associated with epithelial ingrowth

The prophylactic intraoperative use of mitomycin-C (MMC) to prevent haze and scarring after excimer laser surface ablation (phototherapeutic/photorefractive keratectomy [PTK/PRK]) in an eye with a previous laser in situ keratomileusis (LASIK) flap buttonhole with epithelial ingrowth is described. A well-centered buttonhole measuring 2.0 mm in diameter was cut within a thin LASIK flap in an amblyopic eye. Over the next 8 weeks, corneal haze and progressive epithelial ingrowth formed centrally. An early transepithelial PTK/PRK approach was chosen to manage the buttonhole together with the epithelial ingrowth and to treat ametropia before the onset of scarring. The approach included epithelial removal with PTK, application of MMC 0.02% for 1 minute, irrigation, a short waiting period to allow for diffusion, PRK correction of -4.0 diopters without nomogram adjustment, and bandage contact lens. A regimen of prednisolone acetate 1% and ofloxacin 0.03% 5 times a day for 1 week (steroid tapered) was prescribed. Epithelial ingrowth was removed successfully. Minimal haze formation was visible 2 weeks after the retreatment but did not reduce best spectacle-corrected visual acuity (BSCVA) and resolved within the next few weeks. After 6 weeks, uncorrected visual acuity was equal to BSCVA preoperatively (20/50). There was no evidence of recurrent epithelial ingrowth or central scarring after 24 months. Transepithelial PTK/PRK was effective in managing central epithelial ingrowth in a buttonholed LASIK flap. Prophylactic intraoperative use of MMC may reduce haze formation and corneal scarring in early treatments and may also prevent recurrent epithelial ingrowth. This approach may offer faster visual recovery and no risk for a repeated buttonhole creation compared with the widespread recutting a new flap after a couple of months. The optimal application time and concentration of MMC need to be established.     

Photorefractive keratectomy with mitomycin C for the management of a LASIK flap complication following a penetrating keratoplasty

OBJECTIVE: To evaluate the safety and efficacy of photorefractive keratectomy (PRK) with mitomycin C (MMC) following a buttonhole secondary to attempted laser in situ keratomileusis (LASIK) in an eye that had undergone a prior penetrating keratoplasty (PKP). METHODS: Case report and review of the literature. A 26-year-old man underwent PRK with MMC following a buttonhole flap complication after LASIK in an eye that had undergone a PKP for keratoconus. RESULTS: Three months following the procedure, the patient demonstrated a clear cornea and a best-corrected visual acuity of 20/20. CONCLUSION: To our knowledge, this is the first case report of buttonhole during LASIK following a PKP and the use of PRK to treat a LASIK flap complication following a successful PKP. In addition, this is the first case report of prophylactic use of MMC to prevent corneal haze with PRK following PKP. A buttonhole is a rare complication following LASIK for residual refractive error following PKP, which can be successfully managed with PRK and prophylactic MMC.     

Wavefront-guided surface ablation with prophylactic use of mitomycin C after a buttonhole laser in situ keratomileusis flap

PURPOSE: To describe the surgical outcome of a patient who had a previous buttonhole after laser in situ keratomileusis (LASIK) and 3 months later, had wavefront-guided photorefractive keratectomy (PRK) with topical mitomycin C 0.02%. METHODS: A 38-year-old man underwent bilateral LASIK for correction of myopic astigmatism. A buttonhole in his right eye LASIK flap occurred, but the surgeon decided to proceed with ablation due to the small size of the buttonhole. After LASIK, the patient complained of monocular diplopia in his right eye with 20/30 best spectacle-corrected visual acuity. Wavefront analysis showed a large amount of higher order aberrations, especially coma. Slit-lamp examination revealed a moderate buttonhole scar. Three months after LASIK, the patient underwent wavefront-guided PRK with application of topical mitomycin C 0.02% on the stromal bed, for a duration of 2 minutes. RESULTS: One month after wavefront-guided PRK, his uncorrected visual acuity was 20/25 in the right eye, with no symptoms. Best spectacle-corrected visual acuity in the right eye was 20/15 with +0.25 -0.50 x 110 degrees. No haze or scar was seen on slit-lamp examination. Wavefront analysis showed a decrease in higher order aberrations, especially coma and spherical aberration. CONCLUSIONS: Wavefront-guided PRK with prophylactic topical mitomycin C was effective in treating a patient with visual symptoms and loss of BSCVA after a LASIK flap buttonhole. No delayed epithelial healing, side effects or complications were noted due to mitomycin C.     

Corneal haze following PRK with mitomycin C as a retreatment versus prophylactic use in the contralateral eye

PURPOSE: To report photorefractive keratectomy (PRK) treated with mitomycin C (MMC) for previous corneal haze in one eye and PRK with MMC to prevent corneal haze formation in the fellow eye. METHODS: A 40-year-old woman underwent PRK with MMC to treat previous corneal haze (secondary to previous PRK without MMC) for residual refractive error of +0.50 +0.25 x 165 in the left eye and PRK with MMC to prevent corneal haze in the right eye. RESULTS: Postoperative slit-lamp examination revealed no haze in the right eye, but continued mild haze in the left eye. CONCLUSIONS: Treatment with PRK and MMC for previous corneal haze is not as effective as primary PRK with MMC in preventing postoperative corneal haze formation.     

The safety and efficacy of photorefractive keratectomy after laser in situ keratomileusis

PURPOSE: To determine the safety and efficacy of performing photorefractive keratectomy (PRK) in corneas previously treated with laser in situ keratomileusis (LASIK) surgery. METHODS: Fifteen eyes of 14 patients who had initially received LASIK for the treatment of myopia and compound myopic astigmatism were evaluated. Variables included existence of and/or type of flap complication associated with the original LASIK procedure, refractions before and after (3 and 6 months) PRK, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and the development of complications after PRK such as haze, scarring, double vision, or ghosting. RESULTS: All 15 eyes were available for analysis at 6 months. Eleven eyes had experienced flap complications during the initial LASIK procedure and 4 eyes had experienced complications in the LASIK postoperative period. Characteristics prior to performing PRK included 11 myopic and 4 hyperopic eyes. By 6 months after PRK treatment, 87% of eyes had UCVA > or = 20/40, 53% had > or = 20/25, and 40% had > or = 20/20. All eyes had BSCVA of > or = 20/30, with 73% being > or = 20/20. No eye had lost 2 lines of BSCVA and only 1 eye lost 1 line of BSCVA. Sixty percent of eyes were within 1.0 diopters (D) of emmetropia, and 40% were within 0.5 D of emmetropia. A trend towards undercorrection and surgical induction of astigmatism as confirmed by vector analysis was noted. No eye developed significant haze or scarring. CONCLUSIONS: Photorefractive keratectomy may be a safe procedure to perform in corneas previously treated with LASIK surgery. Results show good reduction of refractive error and improvement of UCVA and BSCVA. A significant undercorrection of astigmatism was attributed to surgically induced astigmatism. Further studies are necessary to determine the long-term safety and stability of outcomes.     

The epithelial flap for photorefractive keratectomy

BACKGROUND/AIMS: Epithelial debridement for photorefractive keratectomy (PRK) is associated with pain, slower visual recovery, and may be aetiological in haze production. The aim of this study was to assess the clinical results of a new technique involving raising and replacing of an epithelial flap in photorefractive keratectomy. METHODS: A prospective, non-randomised, comparative, paired eye trial was performed in 72 eyes of 36 patients who underwent PRK with a Nidek EC-5000 excimer laser. For epithelial debridement before PRK, the eyes were divided into two groups. The first eye of each patient was treated with 20% ethanol debridement and the second eye with an epithelial flap which was replaced after treatment. PRK was carried out with the same laser and nomogram in both groups by the same surgeon. Visual and refractive outcome of PRK treatment was compared in both groups. RESULTS: The mean (SD) preoperative mean spherical equivalent (MSE) was -3.61 (1.38) dioptres (D) (range -1.00 D to -7.88 D) with no significant difference between the two groups. After a mean follow up period of 62.6 weeks (range 52-70) the final MSE was +0.07 (0.61) D (range -5.50 D to +4.50 D) in the debridement group and -0.24 (0.43) D in the epithelial flap group. There was no statistically significant difference between the two groups in postoperative MSE. The best corrected visual acuity was better in the epithelial flap group at all visits; this difference was statistically significant (p<0.05). The corneal haze was less in the epithelial flap group and this difference was also statistically significant (p<0.05). CONCLUSIONS: Managing the corneal epithelium as a hinged flap with 20% ethanol is a safe technique with faster visual rehabilitation and reduced haze compared with debridement of the epithelium with alcohol. Further studies need to be performed to compare pain levels postoperatively with the epithelial flap and epithelial debridement.     

Immunohistology of corneal wound healing after photorefractive keratectomy and laser in situ keratomileusis. wachtlin@ukbf.fu-berlin.de.

PURPOSE: The aim of the study was to compare corneal wound healing after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) using conventional, immuno- and enzymohistologic methods. METHODS: Sixteen white Russian rabbits in each group underwent PRK or LASIK. Keratocyte density was recorded from 1 week to 6 months post-operatively on conventional histological sections. Immunohistologic cellular fibronectin and tenascin were used as markers of early epithelial and stromal wound healing in the cornea. The cell damage was demonstrated enzymohistologically using alkaline phosphatase. RESULTS: The reaction was similar in quality with both methods and occurred at sites of simultaneous epithelial and stromal injury. Mild scarring was found around the edge of the flap after LASIK; PRK-treated corneas developed a central subepithelial haze and scarring. A hypocellular region was found in the anterior part of the ablation zone shortly after PRK. Fibroblast migration later led to hypercellularity and subsequent clinical haze formation. After LASIK this reaction was limited to the peripheral entry point of the microkeratome blade around the edge of the corneal flap, where cellular fibronectin and tenascin reactions were positive. An acellular zone was found anterior to the interface after LASIK. The keratocyte damage visualized by alkaline phosphatase was more extensive after PRK than after LASIK. CONCLUSION: The stromal reaction to surgery was more extensive after PRK than after LASIK. A cytokine-mediated interaction between the epithelium and stroma was suggested as the cause of keratocyte cell migration and scar formation.     

Prophylactic mitomycin C to inhibit corneal haze after photorefractive keratectomy for residual myopia following radial keratotomy

PURPOSE: To evaluate the efficacy and safety of mitomycin C (MMC) 0.02% in inhibiting haze formation after excimer laser photorefractive keratectomy (PRK) for residual myopia following radial keratotomy (RK). METHODS: A prospective, nonrandomized, noncomparative interventional case series was conducted of 22 eyes (14 patients) with residual myopia after RK performed at a single institution. All eyes were treated with PRK and a single intraoperative topical application of MMC 0.02% solution for 2 minutes using a soaked cellulose sponge placed over the ablated area. Refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and slit-lamp evidence of cotneal opacity (haze) were evaluated over 12 months. RESULTS: Twelve months postoperatively, 3 eyes showed grade 1 haze, and 2 eyes showed grade 0.5 haze. Twelve months postoperatively, 2 (9%) eyes had UCVA > or = 20/20. No eye before and 17 (77%) eyes after treatment had UCVA > or = 20/40, and no eye before and 9 eyes (40.9%) after treatment had UCVA > or = 20/25. Best spectacle-corrected visual acuity was > or = 20/40 in all (100%) eyes and 21 (95%) eyes before and after treatment, respectively, and > or = 20/25 in 12 (54.5%) eyes before and after treatment. One (4.5%) eye lost 1 line of BSCVA. Mean spherical equivalent refraction achieved was -0.18 diopters (D) (range: -0.75 to +0.50 D) compared to -2.72 D (range: -1.50 to -4.00 D) before treatment. Twelve months after treatment, 19 (85.5%) eyes had a refractive outcome within +/- 0.50 D. CONCLUSIONS: A single intraoperative application of MMC 0.02% for 2 minutes appears to be effective in preventing subepithelial haze after PRK for residual myopia in patients with undercorrection or regression following RK.     

Very late-onset corneal scar triggered by trauma after photorefractive keratectomy

A 54-year-old woman who had photorefractive keratectomy (PRK) more than 10 years earlier presented with a history of being hit in the eye by a tree branch and developing blurred vision a short time later. The corrected visual acuity was 20/100 with localized grade 3 stromal haze. The haze intensified despite initial response to corticosteroids and cyclosporine, and treatment with phototherapeutic keratectomy and 0.02% mitomycin-C (MMC) was effective in restoring corneal clarity and normal vision. Late-onset stromal scar can be triggered by trauma years after PRK. Phototherapeutic keratectomy with MMC can be an effective treatment for late-onset scar. Persistent haze or scar after trauma if PRK had not been performed previously is exceedingly rare. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.     

Laser subepithelial keratomileusis: electron microscopy and visual outcomes of flap photorefractive keratectomy

Laser epithelial keratomileusis (LASEK) is a surgical technique that may be performed in patients with low myopia who are considering conventional photorefractive keratectomy (PRK), in patients with thin corneas, and in patients with professions or lifestyles that predispose them to trauma. Ethanol (18%) is applied for 25 seconds and a hinged epithelial flap is created. After laser ablation, the flap is repositioned over the ablated stroma. Our data showed that epithelial defects occurred in 63% eyes on Day 1. Postoperative pain was absent in 47%. Uncorrected visual acuity of 20/40 or better was achieved in all patients at 1 week. Data from several studies suggest that LASEK may reduce postoperative pain and corneal haze associated with PRK. LASEK offers the potential advantage of avoiding flap-related complications associated with laser in situ keratomileusis and decreasing postoperative pain and corneal scarring associated with PRK. Long-term studies are needed to confirm these potential advantages and to determine the safety, efficacy, and predictability of this surgical technique.     

Laser-assisted subepithelial keratectomy (LASEK) without alcohol versus photorefractive keratectomy (PRK)

PURPOSE: To evaluate epithelial healing and visual outcome after laser-assisted subepithelial keratectomy (LASEK) without alcohol de-epithelialization and to compare this technique to photorefractive keratectomy (PRK) in myopia. METHODS: In a series of 1953 patients undergoing bilateral myopic PRK, an epithelial flap could be obtained by manual de-epithelialization in the left eye of 56 patients without alcohol exposure. The right eye was treated by PRK and the left by LASEK (i.e., repositioning the viable flap after surface ablation). The two eyes were compared in terms of pain, uncorrected visual acuity (UCVA) in decimals, correction achieved, and haze. The epithelial healing pattern was assessed in the LASEK eyes. RESULTS: The flap remained viable, showing a peripheral junction, in 25 eyes (45%). Pain was higher in the PRK eye in 11/56 patients (20%), higher in the LASEK eye in 23/56 patients (41%), and the same in both eyes in 22/56 patients (39%). UCVA at one week was slightly better in the LASEK eyes (median 0.7 versus 0.6, p = 0.002 with Wilcoxon test), but was the same in PRK and LASEK eyes after 1 month (median 0.9 in both). Median haze at 6 months was 0.5 in the PRK eyes and 0 in the LASEK eyes (Wilcoxon p = 0.007). Median postoperative defocus equivalent at 9 months was 0.5 diopters in both the PRK and the LASEK eyes. CONCLUSIONS: Although our study might have selected patients with loose epithelium, LASEK performed by manual de-epithelialization in the absence of alcohol exposure is not less painful than PRK, even in case of flap survival. Visual recovery speed, as well as haze, is slightly better than in PRK, although the difference is clinically negligible.     

Photorefractive keratectomy with 0.02% mitomycin C for treatment of residual refractive errors after LASIK

PURPOSE: To evaluate the efficacy and safety of prophylactic mitomycin C (MMC) during photorefractive keratectomy (PRK) over LASIK flaps for the treatment of residual refractive errors following LASIK. METHODS: In this single center, retrospective clinical study, 30 eyes of 33 patients (mean age 37.2 years) who had MMC (0.02%, 30 to 120 seconds) during PRK for the treatment of residual refractive errors following myopic LASIK were evaluated. The retreatment procedures were performed with a VISX S4 laser with iris registration. All patients underwent slit-lamp microscopy, manifest and cycloplegic refraction, corneal topography, pachymetry, pupillometry, and wavefront analysis pre- and postoperatively. All patients underwent follow-up at 1 day, 1 week, and 1, 3, and 6 months and thereafter as required. RESULTS: Mean time between LASIK and PRK retreatment was 67.3 months (range: 7 to 113 months). No intra- or postoperative complications occurred during primary LASIK or PRK retreatment. Mean spherical equivalent refraction of attempted correction with PRK was -0.94 diopters (D) (range: -2.38 to +0.75 D). At mean 7.1-month follow-up, the average uncorrected visual acuity (UCVA) improved from 20/50 (range: 20/30 to 20/200) to 20/28 (range: 20/15 to 20/70). Twenty-seven of 30 eyes showed improvement in UCVA. Two eyes had subjective improvement of glare symptoms (and objective improvement in higher order aberrations), and one eye lost one line of best spectacle-corrected visual acuity due to unrelated corneal abrasion in the postoperative period. None of the eyes in the cohort developed postoperative haze. CONCLUSIONS: Photorefractive keratectomy with prophylactic MMC (0.02%) is a safe and effective option for treating myopic regression following LASIK. A single intraoperative application of 0.02% MMC for as few as 30 seconds was effective in preventing postoperative haze formation.     

Mitomycin C reduces haze formation in rabbits after excimer laser photorefractive keratectomy

PURPOSE: To investigate the effects of mitomycin C on haze after photorefractive keratectomy (PRK). METHODS: Twenty of 24 rabbits underwent bilateral 193-nm excimer laser PRK to correct -10.00 D of myopia; the remaining four rabbits were not operated (no PRK group). The right eyes of the 20 rabbits were treated with 0.02% mitomycin C during surgery (PRK+MMC group) and the left eyes did not receive 0.02% mitomycin C (PRK alone group). Clinical and histopathologic examinations were performed. RESULTS: The most severe haze in the PRK alone group after PRK reached grade 3; the PRK+MMC group did not exceed grade 1 haze. Statistically significant differences were found between the PRK+MMC and PRK alone groups from week 2 to week 26 after treatment (P<.01). Epithelial thickening appeared for 26 weeks in both PRK groups; no statistically significant differences were found between the two PRK groups (P>.05). A marked reduction of keratocytes in the anterior stroma of the PRK+MMC group was observed. At week 1, 2, and 4 after PRK, keratocytes of the PRK+MMC group were only 3.1+/-2.6, 6.8+/-4.7, and 12.4+/-5.7 keratocytes x 10(4)/microm2, respectively, while those of the PRK alone group were 41.2+/-80, 42.3+/-7.8, and 40.0+/-3.3 keratocytes x 10(4)/microm2, respectively. There were statistically significant differences between the two groups (P<.001). CONCLUSION: A single intraoperative application of topical mitomycin C during PRK in rabbits reduced corneal haze by inhibiting the proliferation of keratocytes.     

Late corneal scarring after retinal detachment surgery 42 months after photorefractive keratectomy

A 42-year-old man had uneventful bilateral nonsimultaneous photorefractive keratectomy (PRK) for severe myopia. Thirty-nine months after the procedure, the patient presented with a retinal detachment (RD) in the right eye. Cerclage, vitrectomy, endolaser, and intravitreal silicone oil tamponade were performed, and the RD was successfully repaired. Three months after vitrectomy and 42 months after PRK, the patient complained of visual impairment in the right eye and photophobia. On slitlamp examination, marked reticular scarring of the central anterior cornea was observed. The occurrence of late-onset corneal haze highlights the need for special attention to patients who have vitrectomy after PRK.     

Photorefractive keratectomy for refractory laser in situ keratomileusis flap striae

Photorefractive keratectomy (PRK) with mitomycin-C (MMC) was performed in 2 patients with visually significant, complicated laser in situ keratomileusis flap striae. These striae had been resistant to multiple treatments, including stretching, suturing, and PRK. The visual symptoms in both patients resolved after PRK with MMC, and both patients were stable 1 year later. Wavefront-guided PRK with MMC may be a viable treatment for patients who have complicated flap striae resistant to standard measures.     

Mitomycin C alters corneal stromal wound healing and corneal haze in rabbits after argon-fluoride excimer laser photorefractive keratectomy.

PURPOSE: To investigate the effects of mitomycin C (MMC) on rabbit cornea wound healing after photorefractive keratectomy (PRK). MATERIALS AND METHODS: Rabbit corneas were stained with dichlorotriazinyl aminofluorescein immediately after PRK. MMC was applied to the right eye and phosphate-buffered salt solution (PBS) to the left. Corneal epithelial wound healing rate and corneal haze were examined. Ultrasound pachymetry was performed. Stromal collagen regeneration was evaluated by fluorescent microscopy. We used terminal deoxyribonucleotidyl transferase-mediated D-uridine 5'-triphosphated-digoxigenin nick-end labeling (TUNEL) assay and transmission electron microscopy (TEM) to evaluate keratocyte apoptosis. RESULTS: In eyes treated with MMC, there was no delay to the healing rate of corneal epithelial wound, and less haze 4 weeks after PRK. Ultrasound pachymetry showed thinner corneal thickness in MMC-treated eyes at week 4. Corneal stromal thickness regression was less in MMC-treated eyes observed by fluorescent microscope at week 4. Keratocyte apoptosis was noted in both MMC- and PBS-treated eyes by TUNEL assay and TEM observation. This study discovered the phenomenon that MMC prolongs keratocyte apoptosis. CONCLUSIONS: Applying MMC after PRK is an effective method to decrease haze formation and corneal stromal thickness regression in rabbit corneas. The effect may be related to MMC prolonging keratocyte apoptosis.     

Delayed epithelial healing following photorefractive keratectomy with mitomycin C treatment

Purpose: To evaluate the epithelial healing following photorefractive keratectomy (PRK) with mitomycin C (MMC) 0.02%. Methods: A total of 1520 eyes of 760 patients with myopia with spherical equivalent between ?1.5 and ?8.0 dioptres underwent PRK during 2004–2008. The epithelium was removed mechanically, and laser ablation was followed by topical application of MMC (0.02%) for 20 seconds. A therapeutic contact lens (TCL), kept in 4°C, was fitted and worn until complete epithelialization. Antibiotic, steroid and diclofenac drops were instilled during the healing phase. Steroid drops were used for 6–8 weeks and gradually reduced. The results were compared with a retrospective analysis of 500 myopic eyes which underwent PRK without MMC therapy during 2002–2004. Results: In 30 MMC treated eyes (2%), epithelial healing was delayed with a stellate defect which healed after 12–14 days. Another fifteen eyes (1%) revealed loose midperipheral epithelium and complete epithelialization took 10–14 days after scraping. Two of these eyes developed recurrent erosion treated by scraping and TCL. Seven eyes (0.5%) revealed delayed healing with paracentral epithelial plaques which were scraped and complete healing took 12–14 days. No final haze was found in the MMC‐treated eyes. In comparison, only 0.8% of the eyes which had undergone PRK without MMC revealed epithelial problems. Haze was found in 8% of these eyes. A statistically significant difference was found between the rate of epithelial problems of the two groups (p ≤ 0.002). Conclusions: MMC (0.02%) applied for 20 seconds post‐PRK was found to delay epithelial wound healing up to 14 days in 3.5% of patients with myopia compared to 0.8% of PRK eyes without MMC application. Final haze was not found despite delayed epithelialization because of MMC treatment.     

Buttonholes during LASIK: etiology and outcome

PURPOSE: To report the clinical features and outcome of eyes with flap buttonhole during LASIK. METHODS: A retrospective review was performed to identify eyes that developed flap buttonhole during Hansatome microkeratome translation. Pre-, intra-, and postoperative data were obtained to identify factors predictive of buttonhole. RESULTS: Five patients with buttonhole were identified from June 2001 through September 2002 (5 [0.06%] eyes of 7672 primary LASIK procedures). Mean patient age was 49.2 +/- 11.3 years (range: 37 to 66 years). Mean preoperative spherical equivalent refraction was 4.92 +/- 2.90 diopters (D) (range: -2.25 to -9.50 D). Mean keratometry was 45.59 +/- 1.15 D (range: 43.90 to 47.60 D). All 5 flap buttonholes occurred in the second of 2 consecutively treated eyes (P = .03). Buttonhole occurred in 2 (0.26%) of 778 eyes where the 160-microm microkeratome plate was used, and 3 (0.06%) of 4350 eyes where the 180-microm plate was used (P = .16). Two eyes received laser ablation at the time of buttonhole formation. In the untreated cases, the buttonhole flap itself caused a myopic spherical change of -0.50 D and 0.70 D of astigmatism. One of 5 eyes lost 2 lines of best spectacle-corrected visual acuity; this eye received laser ablation immediately after buttonhole formation. CONCLUSIONS: Buttonholes are significantly more likely to occur in the second of two consecutively treated eyes. A new blade for the second eye when the flap in the first eye appears to be thin should be considered. Caution should be exercised when considering laser ablation immediately following buttonhole formation.     

Photorefractive keratectomy with mitomycin C versus LASIK in custom surgeries for myopia: a bilateral prospective randomized clinical trial

PURPOSE: To compare photorefractive keratectomy (PRK) with prophylactic use of mitomycin C (MMC) and LASIK in custom surgeries for myopic astigmatism. METHODS: Eighty-eight eyes of 44 patients with a minimum estimated ablation depth of 50 microm were randomized to receive PRK with MMC 0.002% for 1 minute in one eye and LASIK in the fellow eye. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), cycloplegic refraction, slit-lamp microscopy, contrast sensitivity, specular microscopy, aberrometry, and a subjective questionnaire were evaluated. Forty-two patients completed 6-month follow-up. RESULTS: Mean spherical equivalent refraction error before surgery and mean ablation depth were -3.99+/-1.20 diopters (D) and 73.09+/-14.55 microm in LASIK eyes, and -3.85+/-1.12 D and 70.7+/-14.07 microm in PRK with MMC eyes, respectively. Uncorrected visual acuity was significantly better in PRK with MMC eyes 3 months (P=.04) and 6 months (P=.01) after surgery. Best spectacle-corrected visual acuity and spherical equivalent refraction did not differ significantly in the groups during follow-up (P>.05). Significant haze was not observed in any PRK with MMC eye. Mean higher order aberration was lower in PRK with MMC eyes postoperatively compared with LASIK eyes (P=.01). Better contrast sensitivity was observed in PRK with MMC eyes than LASIK eyes (P<.05). The endothelial cell count did not differ significantly between groups (P=.65). In terms of visual satisfaction, PRK with MMC eyes were better rated. CONCLUSIONS: Photorefractive keratectomy with MMC appears to be more effective than LASIK in custom surgery for moderate myopia. During 6-month follow-up, no toxic effects of MMC were evident. Long-term follow-up is necessary to attest its safety.     

Mitomycin C-induced reduction of keratocytes and fibroblasts after photorefractive keratectomy

PURPOSE: To investigate the effects of mitomycin C (MMC) on the number of keratocytes and the proliferation of fibroblasts after photorefractive keratectomy (PRK) and exposure to ultraviolet B (UV-B) irradiation. METHODS: The right eyes of New Zealand White rabbits in Groups 1, 2, and 3 (n = 18 each) underwent PRK to correct -10 diopters with 5 mm optical zone. Sponges soaked with 0.02% MMC were applied to the right eyes of Group 1 rabbits for 2 minutes. Antibiotic ointment was applied daily to all rabbits until the epithelium healed completely, after which 0.02% MMC eye drops were applied twice daily to the right eyes in Group 2 until 4 weeks after PRK. Three weeks after PRK, the right eyes of all the remaining rabbits were exposed to 100 mJ/cm2 C UV-B radiation. Corneal haziness was assessed biomicroscopically using the Fantes scale every 3 weeks. Six eyes of each group were each enucleated 3, 6, and 12 weeks after PRK, and tissue specimens were stained with hematoxylin and eosin and with TUNEL stain. The tissues were evaluated immunohistochemically with antibody to alpha-smooth muscle actin (SMA). Cellular changes in the anterior stroma and epithelial basement membrane were evaluated by electron microscopy. RESULTS: Corneal haze was observed after PRK and was aggravated by UV-B irradiation. A single intraoperative application of MMC immediately after PRK induced opacity and apoptosis of keratocytes. Twelve weeks after PRK, MMC significantly reduced corneal haze, the number of keratocytes, apoptotic cells, and fibroblasts, even after UV-B irradiation. Relatively large numbers of apoptotic and SMA-positive cells were found only in PRK-treated, non-MMC treated rabbits (Group 3), even after 12 weeks. Three weeks after PRK, dying stromal cells showed cell shrinkage, and chromatin condensation was observed in all treated groups by electron microscopy. Twelve weeks after PRK, fewer keratocytes and inflammatory cells were observed just beneath the epithelial layer in Group 1 than in any of the other groups. CONCLUSIONS: MMC is a potent inhibitor of corneal haze induced by PRK. MMC reduced the number of keratocytes and fibroblasts after PRK and UV-B irradiation. Although MMC would improve the clinical results of PRK, it has significant toxicity on corneal keratocytes, which did not disappear until 3 months after PRK.