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.     

Laser-assisted subepithelial keratectomy versus photorefractive keratectomy for the correction of myopia. A prospective comparative study

PURPOSE: To compare the early postoperative visual rehabilitation after laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) for the correction of myopia. SETTING: CODET Aris Vision Institute, Tijuana, Mexico. METHODS: This prospective study included 50 eyes of 25 patients with myopia who received LASEK in 1 eye and PRK in the contralateral eye. Excimer laser corneal ablation was done using the Nidek EC-5000 excimer laser. Patients were seen at 1 and 3 days, 1 week, and 1 month. Discomfort, subjective uncorrected visual acuity (UCVA), objective UCVA, best corrected visual acuity (BCVA), corneal clarity (haze), and time for corneal reepithelialization were analyzed. RESULTS: Seventy-two percent and 80% of the LASEK eyes had more discomfort at 1 day and 3 days, respectively. Eighty percent and 96% of the PRK eyes had better subjective UCVA at 1 day and 3 days, respectively. Corneas were fully reepithelialized at a mean of 3.3 days +/- 0.5 (SD) and 3.6 +/- 0.5 days in the PRK and LASEK groups, respectively. At 1 month, the UCVA was similar in both groups; no eye had lost lines of BCVA or developed haze. CONCLUSIONS: Both LASEK and PRK were effective and safe procedures in the surgical correction of myopia at the 1-month postoperative visit. Patients reported less discomfort and better visual acuity in their PRK eye during the early postoperative period. Patients should be informed that LASEK, whose acronym is similar to that of laser in situ keratomileusis, has a recovery speed that is similar to that of surface laser refractive procedures such as PRK.     

PRK治疗近视术后角膜地形图分析

目的　分析准分子激光屈光性角膜切削术 (photorefractive keratectom y,PRK )治疗近视术后角膜表面形态及偏中心切削。方法　 76例 (1 5 0只眼 )行 PRK,术前屈光度 (- 3.0 0～ - 1 0 .0 0 ) D,平均 (- 6 .0 8± 1 .2 1 ) D。术后 1、3、6、1 2个月行角膜地形图检查。结果　角膜地形图形态分为平滑型、半圆型、钥匙孔型、肾型、中央岛型和不规则型 6种。角膜地形图形态有逐渐变平滑的趋势。术后 3个月以后 ,各种类型所占比例基本稳定。平滑型术后裸眼视力较好。偏中心距离 >0 .5 0 m m时 ,术后视力恢复不良。结论　角膜地形图分析系统能精确测量、分析全角膜的前表面形态 ,观察术后效果、指导手术设计 ,从而提高 PRK治疗近视的准确性、安全性和预测性     

Technical improvements in photorefractive keratectomy for correction of high myopia

PURPOSE: To evaluate the effects of hardware and software improvements in photorefractive keratectomy (PRK) for the treatment of highly myopic eyes. METHODS: A retrospective study was carried out in 554 patients (582 eyes) with myopia between -7.00 and -17.00 D (mean -11.20 +/- 3.60 D) who had undergone PRK using the Aesculap Meditec laser. Group 1 with a 5-mm-diameter single ablation zone; Group 2 with a 5-mm-diameter single zone surrounded by a 2-mm tapered transitional zone; Group 3 and Group 4, same as Group 2 but with the laser upgraded with a smoke aspiration control system (Group 3), and with a computer-controlled fluence (Group 4). RESULTS: In Group 1 at 2 years after PRK (50 eyes), 10 eyes (20%) were within +/-1.00 D of attempted correction and 13 eyes (26%) were within +/-2.00 D. In Group 2 at 2 years (118 eyes), 42 eyes (36%) were within +/-1.00 D of attempted correction and 65 eyes (55%) were within +/-2.00 D. In Group 3 at 2 years (43 eyes), 18 eyes (42%) were within +/-1.00 D of attempted correction and 28 eyes (65%) were within +/-2.00 D. In Group 4 at 2 years (47 eyes), 25 eyes (53%) were within +/-1.00 D of attempted correction and 29 eyes (62%) were within +/-2.00 D. CONCLUSIONS: Software and hardware improvements facilitated PRK correction of high myopia with reasonable predictability, especially if a tapered transition zone was used. At 12 and 24-month follow-up, only the use of a tapered transition zone was associated with a statistically significant improvement in predictability.     

准分子激光屈光性角膜切削术治疗—10D以上近视眼

为了评价准分子激光屈光性角膜切削术（PRK）治疗-10．00D以上高度近视眼的效果．我们对在本中心接受了PRK的114只-10．00D以上高度近视眼的半年随访结果进行了统计分析。分两组：T组≥－10．00D＜－15．00D，83只眼；n组）－15．00D＜－22．OOD，（等值球镜）31只限。术后探眼视力＞1．O（或＞术前最好矫正视力）在Ⅰ组为30．1％，Ⅱ组为25．8％；≥0．5（或比术前最好矫正视力下降≤4行）在Ⅰ组为65．1％，Ⅱ组为58．1％。最好矫正视力下降2行以上在Ⅰ组为9．6％，Ⅱ组为12．9％。剩余屈光度（等值球境）≤－1．00D在Ⅰ组为56．6％，Ⅱ组为18．4％；其均数及标准差在Ⅰ组为-1．14±0．99，Ⅱ组为-1．44±1．10D。角膜上皮下混浊Ⅱ组重于Ⅰ组。结果表明：PRK治疗-10D以上高度近视眼安全、有效，但屈光回退明显，其预测性及稳定性差于-10D以下近视眼。     

Characteristics of correction of myopia by photorefractive keratectomy in patients with presbyopia

Photorefraction keratectomy was performed with a Nidek EC-5000 excimer laser in 29 patients (58 eyes) with slight and medium myopia aged 40-60 years. After 12 months the mean visual acuity in the leading eye without correction was 0.82 +/- 0.12 in patients aged 40-50 (group 1) and 0.76 +/- 0.11 in those aged 51-60 years (group 2). The mean refraction of the leading eye in group 1 was -0.97 +/- 0.02 diopters and in group 2 0.72 +/- 0.04 diopters. In group 1 the resultant undercorrection was -1.6 +/- 0.4 diopters (107% of planned undercorrection) and in group 2 -1.8 +/- 0.4 diopters (72% of planned undercorrection). The proposed method effectively corrects slight and medium myopia in patients of presbyopia age. 82% patients were satisfied with the results of treatment: 67% of them did not need eyeglasses for reading and 54% could drive a car without eyeglasses.     

准分子激光角膜切削术治疗近视的并发症

为分析准分子激光角膜切削术（ＰＲＫ）治疗近视的并发症，对１３９例（２５７眼）ＰＲＫ术后随访半年至一年。结果表明：术后一年，低中度和高度组各有１眼最佳矫正视力丢失二行，分别占２．５％和３．３％；低中度和高度组的角膜上皮下１级混浊分别为１０．８１％和１５．１６％，２级混浊分别为２．７３％和０％；激素性高眼压，在发生率最高的３个月时，可分别达２４．３７％和２５．３２％，但这种反应性的眼压升高只是暂时的，容易控制；过矫和散光增加的发生率均较低，主要与术者的经验有关。随着术者经验的提高、手术设计的完善及术后用药的研究，这些并发症会降到最低水平。ＰＲＫ是安全、有效的。     

LASEK and photorefractive keratectomy for myopia: clinical and confocal microscopy comparison

PURPOSE: To compare postoperative visual acuity and corneal morphology after laser epithelial keratomileusis (LASEK) versus photorefractive keratectomy (PRK) in the correction of low to moderate myopia. METHODS: In a double-blind, randomized clinical trial, 50 myopic patients (mean: -4.5 +/- 1.35 diopters) were randomized to receive LASEK in one eye and PRK in the fellow eye. No mitomycin C eye drops were used in this study. Patients were observed daily for 4 days, then at 1 month and every 3 months up to 1 year. Uncorrected and best-corrected visual acuity (UCVA and BSCVA), manifest refraction, corneal epithelium healing time, postoperative pain, and corneal haze were evaluated. Corneal wound healing was quantified with corneal confocal microscopy. RESULTS: Refractive error, UCVA, and BSCVA were not statistically different between eyes treated with LASEK and PRK. Corneal epithelium healing time was 2.52 +/- 0.99 days in the eyes treated with PRK and 2.29 +/- 0.52 days in the eyes treated with LASEK (P=.22). The postoperative pain score was 2.17 +/- 0.87 in the eyes treated with PRK and 2.62 +/- 0.60 (P=.02) in the eyes treated with LASEK. Corneal confocal microscopy showed fewer stromal activated keratocytes and less extracellular matrix deposition in the eyes treated with LASEK than in the eyes treated with PRK at 1 month postoperatively (P=.003). CONCLUSIONS: LASEK is an effective and safe procedure for low to moderate myopia, but it seems more painful until full corneal reepithelization. In the early postoperative period, the corneal wound healing process is significantly less intense in eyes treated with LASEK than in eyes treated with PRK. The role of LASEK in corneal wound healing modulation remains controversial.     

Eight-year follow-up of photorefractive keratectomy for myopia

PURPOSE: We evaluated 8-year results of excimer laser photorefractive keratectomy (PRK) for myopia in terms of stability and late complications. METHODS: Ninety-two myopic eyes of 55 patients were treated with a single-step method using an Aesculap-Meditec MEL 60 excimer laser with a 5.0-mm ablation zone. Treated eyes were divided into three groups according to preoperative refraction: low myopes (< or = -6.00 D), medium myopes (-6.10 to -10.00 D), and high myopes (>-10.00 D). RESULTS: Change in myopic regression stabilized in all myopia groups within 12 months, although a small myopic shift occurred up to 8 years after PRK. Mean change in refraction between 2 and 8 years was -0.42 +/- 0.48 D for low myopes, -0.37 +/- 0.34 D for medium myopes, and -0.41 +/- 0.50 D for high myopes. The percentage of eyes within +/- 1.00 D of emmetropia 8 years after PRK was 78.3% in the low myopia group, 68.8% in the medium myopia group, and 57.1% in the high myopia group. One eye lost 2 lines of best spectacle-corrected visual acuity due to irregular astigmatism. In 13.0% of eyes, a residual trace corneal haze was observed, which had no effect on visual acuity. Apart from the loss of 2 lines of BSCVA in one eye, there were no other late complications during the study period. CONCLUSIONS: The mean change in refraction between 2 and 8 years was less than -0.50 D, regardless of preoperative refraction, and may be attributed to natural age-related refractive change. The appearance of residual corneal haze after 8 years correlated with the amount of myopic correction. PRK was a safe and stable surgical procedure in this group of patients.     

准分子激光二次切削治疗近视性角膜切削术后欠矫

本研究共１５人（２３眼）于准分子激光角膜切削术后因欠矫而实施二次切削。术前平均屈光度为－９．８６Ｄ（－５．００—－２０．００Ｄ），其中２眼为中度近视（－３．２５—－６．００Ｄ），６眼为高度近视（－６．２５—－９．００Ｄ），１５眼为超高度近视（≥－９．２５Ｄ）。准分子激光二次切削采用治疗性角膜切削术（ＰＴＫ）和光学性角膜切削术（ＰＲＫ）相结合的方法。术后６个月随访结果表明：９１％的裸眼视力≥０．５，７０％的裸眼视力≥１．０，７０％的屈光度在±１．００Ｄ，角膜无明显混浊。由此证明：准分子激光二次切削治疗近视性角膜切削术后欠矫及角膜混浊是有效的。     

Ten-year follow-up of photorefractive keratectomy for myopia

Background  

The aim of this study is to evaluate the long-term (10-year) outcome of excimer laser photorefractive keratectomy (PRK) on myopic eyes.     

Five-year follow-up of photorefractive keratectomy for myopia

PURPOSE: To analyze long-term results of photorefractive keratectomy (PRK) for myopia and myopic astigmatism. METHODS: This retrospective study included 15 eyes of 8 patients who were examined annually for 5 years after PRK. The Nidek EC-5000 laser with an ablation zone of 5.0 mm was used. Evaluations included spherical equivalent manifest refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), corneal haze, and corneal astigmatism calculated by Fourier analysis of videokeratography data. RESULTS: A tendency toward myopic regression was most evident within the first postoperative year, with manifest refraction changing from +0.80 +/- 1.62 D at 1 week to -0.45 +/- 0.70 D at 1 year postoperatively (P = .007). Regression continued after the second postoperative year. There was a statistically significant difference between manifest refraction at 2 years (-0.36 +/- 0.75 D) and 5 years (-1.11 +/- 1.12 D) (P = .002). Postoperative UCVA stabilized from 3 months up to 3 years, but slightly deteriorated at 4 years and thereafter due to the myopic refractive shift. BSCVA remained stable throughout the 5-year follow-up period. Several eyes developed mild corneal haze after surgery, but haze was minimal in the majority of patients by 1 year and continued to fade over time. The asymmetry component of the cornea significantly increased after surgery, with all postoperative values significantly higher than before PRK (P < .05). Higher order irregularity increased after surgery, with a statistically significant difference between preoperative and 1 year postoperative (P < .05), but values after 2 years were not different from preoperative baseline. CONCLUSION: Fifteen eyes with a baseline refraction of -3.00 to -9.00 D had PRK with the Nidek EC-5000 laser and a 5-mm-diameter ablation zone. Myopic regression occurred in the first year, with continued mild regression of approximately -0.75 D between 2 and 5 years. Nevertheless, the results show the procedure was relatively safe and effective in this group.     

准分子激光角膜上皮瓣下磨镶术与准分子激光屈光性角膜切削术治疗近视的比较

目的　研究准分子激光角膜上皮瓣下磨镶术 (LASEK)与准分子激光屈光性角膜切削术(PRK)在治疗 - 8 0 0D以下近视的异同。方法　 4 6例近视度数在 - 1 75～ - 8 0 0D的患者在双眼同时治疗时 ,其中一只眼行PRK治疗 ,另一只眼行LASEK治疗 ,观察上皮愈合时间 ,记载疼痛程度 ,对比术后 6个月内视力、屈光状态及角膜上皮下雾状混浊 (Haze)程度。结果　LASEK组上皮愈合时间平均为 3 4 9d ,PRK组为 2 87d ,两者差异有显著意义 (P <0 0 5 ) ;平均疼痛指数LASEK组为 2 0 4 ,PRK组为 2 4 5 ,差异有显著意义 (P <0 0 5 ) ;术后 6个月内两组间视力及屈光度恢复的差异无显著意义 (P>0 0 5 ) ,并发症的发生无差异。LASEK组术后Haze程度明显低于PRK组 (P <0 0 5 )。结论　LASEK可以和PRK一样安全有效地治疗低于 - 8 0 0D的近视 ,并且与PRK相比 ,可以降低早期疼痛水平 ,减少Haze并发症的发生。