丝裂霉素预防准分子激光屈光性角膜切削术后角膜混浊的临床研究

目的:探讨准分子激光屈光性角膜切削术中使用0.2g/L丝裂霉素(MMC)预防术后角膜上皮下混浊(haze)的安全性、有效性。方法:对120例(240眼)屈光不正的患者进行准分子激光屈光性角膜切削术,术中使用0.2g/L丝裂霉素,作用时间为20~90s,观察术后角膜上皮愈合时间、观察术后1,3,6,12mo时裸眼视力、矫正视力、屈光状态、haze形成情况及并发症、角膜内皮细胞计数等。结果:角膜上皮愈合时间为3.01±0.72d;手术前后角膜内皮细胞计数统计学上无显著性差异(P=0.62);术后1,3,6,12mo时裸眼视力、矫正视力、屈光状态统计学上无显著性差异;术后6mo0~0.5级haze218眼(90.8%),1级haze21眼(8.75%),2级haze1眼(0.83%),术后12mo1级haze12眼(5%);术后未见丝裂霉素毒性反应及并发症。结论:使用0.2g/L丝裂霉素预防准分子激光屈光性角膜切削术后角膜上皮下混浊安全、有效。     

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.     

Mitomycin C, ceramide, and 5-fluorouracil inhibit corneal haze and apoptosis after PRK

PURPOSE: To investigate the effects of mitomycin C (MMC), ceramide, and 5-fluororacil (5-FU) on haze after photorefractive keratectomy (PRK) and exposure to ultraviolet B (UVB) radiation. METHODS: The right eyes of 42 New Zealand white rabbits were treated with PRK to correct -10 diopter with a 5-mm optical zone. Sponges soaked in 0.02% MMC, 10 or 40 micromol/L ceramide, or 0.5% 5-FU were applied to the right eyes of 6 rabbits each, and a tarsorrhaphy was performed. Eight weeks after complete healing, topical 0.02% MMC or 0.5% 5-FU was applied twice daily to the right eyes of 6 rabbits that had previously received PRK but no topical medication. The control group of 6 rabbits was treated only with PRK. Three weeks after PRK, all the laser-treated eyes were exposed to 100 mJ/cm UVB radiation. Corneal haze was assessed biomicroscopically every 2 weeks using the Fantes scale. Eyes were enucleated 2, 7, and 13 weeks after PRK, and tissue specimens were stained with hematoxylin and eosin and with Apostain. RESULTS: Corneal haze was observed in all rabbits after PRK and was aggravated by UVB irradiation. When applied immediately after PRK, MMC induced corneal opacity and apoptosis of keratocytes, but, at later times, this reagent significantly suppressed opacity, Apostain-positive keratocytes and reactivation of keratocytes, even after UVB irradiation. In contrast, ceramide and 5-FU suppressed corneal opacity after PRK, but this effect was not sustained after UVB irradiation. CONCLUSIONS: MMC is a potent inhibitor of haze induced by PRK and UVB irradiation. Throughout the process of corneal wound healing, the severity of apoptosis and reactivation of keratocytes was closely correlated with haze formation.     

PRK+MMC与LASEK治疗高度近视效果比较

目的比较PRK术中预防性使用丝裂霉素C（MMC）治疗高度近视和LASEK治疗高度近视的疗效.方法将高度近视（-6.0～-10.0D）随机分为PRK＋MMC组40例（80眼）和LASEK组38例（76眼）.另以早年PRK手术屈光状态与之相似的40例（80眼）作为对照.PRK＋MMC组在PRK术中使用0.02%MMC,LASEK组采用常规LASEK,评价术后角膜上皮下雾状浑浊（haze）,屈光回退、视力及角膜内皮细胞改变等情况.结果PRK＋MMC组未出现2级或2级以上haze,无术后矫正视力下降者,术后欠矫小于-0.5D者70眼;LASEK组有6眼出现2级及2级以上haze,有6眼出现术后矫正视力下降,术后欠矫小于-0.5D者56眼.两组的差异有显著性.使用MMC未见明显毒副作用.结论PRK术中预防性使用MMC,在术后减少haze、防止屈光回退、改善视力方面较LASEK为优.     

丝裂霉素对PRK术后角膜上皮下雾状混浊的影响

目的:探讨丝裂霉素(mitomycin C,MMC)对准分子激光角膜切削术(photorefractive keratectomy,PRK)后角膜上皮下雾状混浊(haze)的影响。方法:随即对122例244眼患者进行PRK手术,等值球镜约在-4.00～-9.00D。其中A组(MMC组)61例122眼PRK术中将浸有0.2g/L丝裂霉素棉签,浸润角膜中央切削区,持续时间约25～30s后,用10～20mL平衡盐水液冲洗;B组(BBS组)61例122眼,作为对照组,PRK术后仅用平衡盐水冲洗。两组患者术后均配戴同一型号博士伦隐形眼镜,用同一组PRK术后常规眼药滴眼,并于术后1wk;0.5,1,3,6,8mo;1a,由同一技术人员在裂隙灯下观察角膜情况及haze评分。结果:不同时间MMC组和BBS组角膜上皮愈合时间相比差异无显著意义;术后观察3～18mo,A组haze明显轻于B组,差异具有统计学意义(P=0.014),且无明显毒副作用及其它并发症发生。结论:PRK术后haze的形成与多种因素有关,但PRK术后应用浸有MMC的棉签浸润切削区可有效的抑制haze的形成。     

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.     

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.     

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.     

Evaluation of the prophylactic use of mitomycin-C to inhibit haze formation after photorefractive keratectomy

PURPOSE: To evaluate the results of the prophylactic use of mitomycin-C to inhibit haze formation after excimer laser photorefractive keratectomy (PRK) for medium and high myopia in eyes that were not good candidates for laser in situ keratomileusis (LASIK). SETTING: Carones Ophthalmology Center, Milan, Italy. METHODS: This prospective randomized masked study comprised 60 consecutive eyes (60 patients). The inclusion criteria were a spherical equivalent correction between -6.00 and -10.00 diopters (D) and inadequate corneal thickness to allow a LASIK procedure with a residual stromal thickness of more than 250 microm. The eyes were divided into 2 groups according to the randomization protocol. After PRK, the study group eyes were treated with a single intraoperative dose of mitomycin-C (0.2 mg/mL), applied topically with a soaked microsponge placed over the ablated area and maintained for 2 minutes. The control eyes did not receive this treatment. Refraction, uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and slitlamp evidence of corneal opacity (haze) or other visible complications were evaluated. RESULTS: No toxic or side effects were encountered postoperatively. No study group eye had a haze rate higher than 1 during the 6-month follow-up; 19 eyes (63%) in the control group did (P =.01). At 6 months, the between-group difference in the refractive outcome was statistically significant (P =.05), with 26 study group eyes (87%) and 14 control eyes (47%) within +/-0.50 D of the attempted correction. No study group eye had a BCVA loss during the follow-up; 7 control eyes had lost 1 to 3 lines at 6 months (P =.0006). CONCLUSIONS: The prophylactic use of a diluted mitomycin-C 0.02% solution applied intraoperatively in a single dose after PRK produced lower haze rates, better UCVA and BCVA results, and more accurate refractive outcomes than those achieved in the control group.     

Photorefractive keratectomy in the correction of astigmatism using Schwind Amaris 750s laser

AIM:To evaluate the results of three photorefractive keratectomy (PRK) procedures in the treatment of astigmatism.METHODS:In thisretrospective comparative case series, 89 eyes of 50 patients who underwent PRK treatment for astigmatism were enrolled. The patients were divided into 3 groups based on the PRK procedure:Group 1:PRK without mitomycin-C (MMC) application, Group 2:PRK with MMC application, and Group 3:Trans-Photorefractive Keratectomy(T-PRK). The efficacy, safety, predictability, and complications of treatment were assessed at 1, 3 and 6 months after the treatment.RESULTS: At postoperative 6 months, the percentage of postoperative uncorrected visual acuity (UCVA) of 20/20 or better was 55.6% (20 eyes) in group 1, 75% (15 eyes) in group 2, and 75.8% (25 eyes) in group 3 (P=0.144).The percentage of postoperative best corrected visual acuity (BCVA) of unchanged or gained ≥1 lines was 80.6% (29 eyes) in group 1, 70% (14 eyes) in group 2, and 90.9% (30 eyes) in group 3 (P=0.151). The percentage of postoperative BCVA of lost ≥2 lines was 11.1% (4 eyes) in group 1, 20% (4 eyes) in group 2, and 6.1% (2 eyes) in group 3. The mean manifest refractivespherical equivalent (MRSE) and mean cylindrical refraction were not significantly different among the each groups (P>0.05). At postoperative 6 months, the percentage of MRSE of within ±0.50 D was 100% (36 eyes) in Group 1, 100% (20 eyes) in Group 2, and 93.9% (31 eyes) in Group 3. At the each follow-up period, there was no significant difference in number of eyes with haze and mean haze score(P>0.05).CONCLUSION:The study showed that PRK without MMC, PRK with MMC and T-PRK appears to have similar effectiveness, safety and predictability in the treatment of astigmatism. The incidence of haze was also similar between the three groups.     

Laser in situ keratomileusis for residual myopia after photorefractive keratectomy

PURPOSE: To evaluate the efficacy and safety of laser in situ keratomileusis (LASIK) for myopic regression and undercorrection after photorefractive keratectomy (PRK). SETTING: The Eye Institute, Sydney, Australia. METHODS: Fifty eyes of 32 patients were treated by LASIK for residual myopia following primary PRK. The mean spherical equivalent refraction (SEQ) was -2.92 diopters (D) +/- 1.57 (SD) (range -0.75 to -7.88 D). The mean refractive cylinder was 0.96 +/- 0.74 D (range 0 to 3.50 D). For analysis, the eyes were divided into 2 groups: those with 0 or low corneal haze (Group 1) and those with severe corneal haze (Group 2). In Group 1, the SEQ was -1.99 +/- 0.79 D (range -0.75 to -3.75 D) and in Group 2, -3.77 +/- 1.62 D (range -0.75 to -7.90 D). The procedure was performed using the Chiron Automated Corneal Shaper and the Summit Apex Plus laser. The mean interval between PRK and LASIK was 25 months (range 9 to 59 months). The following parameters were studied before and after LASIK retreatment: SEQ, mean refractive cylinder, uncorrected visual acuity (UCVA), and best corrected visual acuity (BCVA). Complications after LASIK retreatment were evaluated. RESULTS: Six months after LASIK, the mean SEQ in all eyes was -0.65 +/- 0.86 D (range +1.50 to -3.35 D); 70.0% of eyes were within +/-1.00 D of emmetropia and the UCVA was 6/12 or better in 72.5%. The mean SEQ in Group 1 was -0.22 +/- 0.55 D (range -0.88 to -1.50 D) and in Group 2, -0.97+/- 0.92 D (range 0.12 to -3.25 D); the UCVA was 6/12 or better in 94.0% of eyes in Group 1 and in 56.0% in Group 2. No statistically significant between-group difference was found in lines of Snellen acuity lost or gained at 6 months. No eye lost more than 1 line of BCVA. CONCLUSIONS: Laser in situ keratomileusis appears to be a safe, effective, and predictable procedure for treating eyes with 0 or low haze with residual myopia after PRK. It is less predictable in eyes with severe haze.     

丝裂霉素抑制PRK后haze形成及屈光回退的研究

目的评价在高度近视的PRK手术中预防性使用丝裂霉素（MMC）抑制术后角膜上皮下混浊（haze）和屈光回退的效果，以寻求更佳的屈光手术方式。方法将不宜接受LASIK手术的高度近视患者（－6．0～－10．0D）按协议随机分为研究组40例（80眼）和对照组38例（76眼），研究组患者在PRK手术中使用0．02％丝裂霉素，对照组患者采用常规的PRK手术，术后两组用药方案一样，评价术后角膜上皮下混浊（haze）、角膜上皮修复、屈光状态、裸眼视力，矫正视力、角膜内皮细胞改变等情况。结果研究组未出现一眼2级或2级以上haze，无一眼出现术后最佳矫正视力下降，术后达到最佳矫正视力所需屈光改变小于－0．5D有70眼；对照组有26眼出现2级或2级以上haze，有14眼出现术后矫正视力下降，术后达到最佳矫正视力所需屈光改变小于－0．5D有37眼。研究组与对照组的差异有显著性。使用丝裂霉素未见明显毒副作用。结论PRK手术中预防性使用0．02％丝裂霉素，对术后减少角膜雾状混浊，防止屈光回退，改善裸眼视力和最佳矫正视力，是安全有效的。     

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.     

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.     

Topical thiotepa treatment for recurrent corneal haze after photorefractive keratectomy

PURPOSE: To describe the use of topical thiotepa in the treatment of recurrent haze after photorefractive keratectomy (PRK). SETTING: Gimbel Eye Centre, Calgary, Alberta, Canada. METHODS: Five patients with recurrent haze after myopic PRK were retreated with phototherapeutic keratectomy and topical thiotepa. Before retreatment, the best corrected visual acuity (BCVA) ranged from 20/40 to 20/200. Follow-up ranged from 3 to to15 months. RESULTS:Haze, uncorrected visual acuity (UCVA), and BCVA improved in all patients. Three eyes had a UCVA of 20/20(-2) or better and a BCVA of 20/20(-1) or better. The other 2 eyes experienced regression of the myopia and astigmatism and had a BCVA of 20/25(-1) or better. CONCLUSION: Topical thiotepa appeared to be an effective treatment for recurrent corneal haze following myopic PRK.     

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.     

Corneal haze among blue eyes and brown eyes after photorefractive keratectomy

BACKGROUND: To compare the incidence and severity of corneal haze after photorefractive keratectomy (PRK) among white patients with blue eyes and Saudi patients with brown eyes. DESIGN: Retrospective, nonrandomized, comparative trial. PARTICIPANTS: A total of 150 patients (71 females and 79 males) were included in this study. Two hundred sixty-six eyes of 150 patients were subjected to PRK. One hundred blue eyes of 50 white patients and 166 brown eyes of 100 Saudi patients were included in this study. METHODS: Two hundred sixty-six eyes of 150 patients were subjected to PRK with the Chiron Technolas Keracor 117C for the correction of myopia and astigmatism. MAIN OUTCOME MEASURES: All patients had complete ophthalmologic examinations, visual acuity testing, intraocular pressure, pachymetry, corneal haze assessment (0-4+), and computerized corneal topography. RESULTS: There were 266 eyes of 150 patients with 100 blue irides and 166 brown irides. The spherical equivalent was -0.50 diopter (D) to -8.75 D. The mean postoperative spherical equivalent at 6 months was -0.063 D (standard deviation [SD], +/-0.595) in blue eyes compared to -0.28 D (SD, +/-0.683) in brown eyes (P = 0.006). Ninety-five (95%) of 100 of the blue eyes achieved +/- 1 D of attempted correction compared to 148 (89.2%) of the 166 brown eyes. All patients with blue eyes had a visual acuity of 20/30 or better compared to 153 (92.2%) of the 166 brown eyes (P = 0.009). Forty-eight (18.04%) eyes had minimal to mild haze, 3 (1.12%) eyes had moderate haze, and 2 (0.75%) eyes had severe haze. The incidence of corneal haze among brown eyes was 48 (28.9%) of 166 eyes compared to 5 (5%) of 100 in blue eyes (P < 0.001). The difference remained significant after adjustment for age and gender with a P value of 0.0283. The relative risk for developing haze in brown eyes was found to be 7.72. CONCLUSION: The incidence of corneal haze after PRK was significantly higher among Saudi patients with brown irides than among white patients with blue irides. This suggests that racial factors may play a role in the development of corneal haze.     

Laser-assisted subepithelial keratectomy and photorefractive keratectomy for the correction of hyperopia. Results of a 2-year follow-up

PURPOSE: To evaluate and compare the efficacy, safety, predictability, and stability of laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) for low to moderate hyperopia with a 2-year follow-up. SETTING: Department of Ophthalmology, Masaryk University Hospital, Brno, Czech Republic. METHODS: This prospective comparative single-surgeon study included 216 eyes of 108 patients with hyperopia who received PRK in 1 eye and LASEK in the contralateral eye. The mean patient age was 38.3 years (range 25 to 58 years). The mean preoperative spherical equivalent (SE) cycloplegic refraction was +3.67 diopters (D) +/- 1.15 (SD) (range +2.00 to +5.00 D), and astigmatism was less than 1.00 D. In each patient, PRK was performed in 1 eye (Group A) and LASEK was performed in the other eye (Group B) using the Nidek EC-5000 excimer laser. Postoperative uncorrected visual acuity (UCVA), best corrected visual acuity, contrast sensitivity, manifest and cycloplegic refractions, refractive stability and predictability, postoperative pain, and corneal haze were examined and statistically analyzed. A P value less than 0.05 was considered significant. RESULTS: At 1 week, the UCVA was 20/40 or better in 58% of PRK eyes and 85% of LASEK eyes (P =.037); at 2 years, it was 20/40 or better in 81% and 91%, respectively (P =.076). At 2 years, the UCVA for near was N8 or better in 73% of PRK eyes and 89% of LASEK eyes (P =.064). No patient lost 2 or more lines of Snellen visual acuity. The safety index was 1.03 in PRK eyes and 1.08 in LASEK eyes. Refractive stability was achieved at 6 months in LASEK eyes and at 12 months in PRK eyes. The mean SE cycloplegic refraction decreased from +3.58 D (PRK eyes) and +3.76 D (LASEK eyes) at baseline to +0.74 D and +0.32 D, respectively, at 2 years; in 57% and 78% of eyes, respectively, the refraction was within +/-0.50 D of the targeted refraction. Peripheral corneal haze scores at 3 to 9 months and pain scores at 1 to 3 days were significantly lower in the LASEK group than in the PRK group. CONCLUSIONS: Laser-assisted subepithelial keratectomy for hyperopia up to +5.00 D provided good visual and refractive results. It significantly reduced postoperative pain, grade of peripheral ring-shaped corneal haze, and regression of hyperopia. Hyperopic LASEK provided quicker visual recovery and achieved better efficacy, predictability, and refractive stability than hyperopic PRK.     

Clinical outcomes of transepithelial photorefractive keratectomy versus femtosecond laser assisted keratomileusis for correction of high myopia in South Egyptian population

AIM: To evaluate the safety and efficacy of transepithelial photorefractive keratectomy(t-PRK) with adjuvant mitomycin C(MMC) versus femtosecond laser assisted keratomileusis(Femto-LASIK) in correction of high myopia.METHODS: Prospective randomized comparative study including 156 eyes of 156 patients with high myopia and a spherical equivalent refraction(SER) <-6.00 D. They were divided randomly into two groups: Group A included 72 eyes treated with t-PRK with adjuvant MMC and Group B included 84 eyes treated with Femto-LASIK. Visual acuity, SER, corneal topography, pachymetry and keratometry were assessed for 12 mo postoperatively.RESULTS: The preoperative mean SER was-8.86±1.81 and-9.25±1.70 D in t-PRK MMC group and Femto-LASIK respectively(P=0.99) which improved to-0.65±0.43 D and-0.69±0.50 D at 12 mo follow up. Mean SER remained stable during the 12 mo of follow-up, with no statistically significant difference between the two groups(P=0.64). In t-PRK MMC group, only six eyes needed retreatment after six months of follow up. And two eyes showed haze(one reversible haze grade 2, while the other had dense irreversible haze grade 4).CONCLUSION: t-PRK MMC provides safe and satisfactory visual outcomes and acceptable risk as Femto-LASIK in patients with high myopia.     

Scraping and mitomycin C to treat haze and regression after photorefractive keratectomy for myopia

PURPOSE: To evaluate the efficacy, safety, and predictability of therapeutic scraping and application of a diluted 0.02% mitomycin C solution to treat haze and regression after photorefractive keratectomy (PRK) for myopia. METHODS: We performed a non-comparative, non-randomized retrospective study of 35 eyes of 30 patients who had previously undergone PRK for myopia and developed haze and regression after treatment. The range of refractive error after regression was -0.75 to -5.50 D (mean -2.92 D). Haze, ranging from grade 3 to 4 (scale: 0 to 4) caused a best spectacle-corrected visual acuity loss of 1 to 6 Snellen lines. All eyes were treated 6 to 12 months after PRK by scraping the stromal surface and application of a 0.02% mitomycin C solution for 2 minutes using a soaked merocel sponge. No laser ablation was performed. Corneal transparency, refractive error, and visual outcomes were evaluated over a 12-month follow-up period. RESULTS: All eyes had significant improvement in corneal transparency. Thirty-one eyes had haze grades lower than 1, which were maintained over time. Only four eyes showed haze grades 1 to 2 and two of them needed further treatment using the same technique. At 12 months after treatment, all eyes were within +/-1.50 of original intended correction (mean 0.04 +/- 0.63 D). BSCVA improved in all eyes. No toxic effects were observed during re-epithelialization or during follow-up. CONCLUSION: Single application of diluted mitomycin C 0.02% solution following scraping of the corneal surface was effective and safe in treating haze and regression after PRK.