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.     

One-year outcomes of a bilateral randomized prospective clinical trial comparing laser subepithelial keratomileusis and photorefractive keratectomy

PURPOSE: To compare laser subepithelial keratomileusis (LASEK) and photorefractive keratectomy (PRK) in different eyes of the same patients in terms of visual acuity, refractive error, and complications over 1 year. METHODS: This prospective, randomized, double-masked study comprised 30 active-duty military personnel with myopia who underwent LASEK in one eye and PRK in the other eye. RESULTS: Twenty-eight patients' results were available for 1-year follow-up. The primary outcome measures were visual acuity and refractive error. The mean visual acuity for the LASEK group was 1.56 and 1.67 for the PRK group (z = -0.18, P = .15). The mean spherical equivalent refraction for the LASEK group was -0.007 D and +0.124 D for the PRK group (t = 0.982, P = .40). No significant differences were noted in visual acuity or refractive error in the eyes that had LASEK versus the eyes that had PRK. CONCLUSIONS: After 1-year follow-up, LASEK and PRK show similar levels of visual acuity and refractive error.     

Topography-controlled excimer laser photorefractive keratectomy

PURPOSE: To assess whether photorefractive keratectomy (PRK) controlled by videokeratography can successfully treat refractive errors in eyes with corneal irregularities and improve spectacle-corrected visual acuity. METHODS: In a prospective clinical study, PRK was performed in 10 eyes of 10 patients. Reason for surgery was irregular astigmatism after penetrating keratoplasty, corneal irregularity after corneal scarring, corneal astigmatism in keratoconus, and decentration after myopic and hyperopic PRK. Excimer ablation was controlled by preoperative videokeratography (Orbscan II, Orbtek) using the MEL-70 system from Aesculap Meditec. Follow-up was 6 months. RESULTS: Concerning manifest refraction, the sphere was reduced on average from +1.92 to +0.57 D, 6 months postoperatively. Cylinder changed from -1.95 D on average to -0.30 D at 6 months postoperatively. There was improvement of uncorrected visual acuity of 2 or more lines in 5 eyes and no change in 5 eyes 6 months postoperatively. Spectacle-corrected visual acuity improved in 2 eyes by 2 to 3 lines, in 9 eyes by 1 to 3 lines, and showed no change in 1 eye. CONCLUSION: Videokeratography-controlled PRK improved refractive errors in irregular corneas with improvement of spectacle-corrected visual acuity.     

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.     

LASIK和SBK术后外伤性角膜瓣移位的处理

目的:探讨准分子激光角膜原位磨镶术(laser in situ keratomileusis,LASIK)和准分子激光角膜前弹力层下磨镶术(Sub-Bowman’s keratomileusis,SBK)术后外伤性角膜瓣移位的处理。方法:对14例14眼LASIK和SBK术后因外伤导致角膜瓣移位的患者,经及时手术处理,合理用药,视力恢复良好。结果:选取的14例中13例治疗术后1wk视力均达到0.8以上,角膜透明,无1例患者角膜出现角膜瓣皱褶、上皮植入、角膜瓣溶解。1例患者因角膜瓣全部移位,治疗术后1wk视力0.1,角膜全层水肿,角膜瓣下皱褶不明显,下方瓣缘裂伤处有1～2mm宽的上皮植入。术后6mo,视力达到1.0,角膜完全透明。结论:及时正确处理LASIK和SBK术后外伤性角膜瓣移位均能获得良好视力。     

Early pellucid marginal corneal degeneration: case reports of two refractive surgery candidates.

PURPOSE: To report two refractive surgery candidates who demonstrated early corneal topographic findings of pellucid marginal degeneration. METHODS: Case reports. RESULTS: Two candidate patients for corneal laser surgery were examined. The patients had normal examinations, including normal slit lamp biomicroscopy results and corrected visual acuity that was 20/20 or better in each eye. The corneal topography in one eye of patient I and both eyes of patient 2 was characterized by the presence of irregular astigmatism and inferior corneal steepening with a pattern consistent with pellucid marginal degeneration. Marked asymmetry between the eyes was noted. The inferior cornea was thinner than the central cornea in both eyes of each patient. CONCLUSION: Patients with early corneal ectasia often present as refractive surgery candidates with normal corrected visual acuity and normal pachymetry of the central cornea. Corneal topography and regional pachymetry measurements can be used to identify these patients. Patients with pellucid marginal degeneration are not good candidates for refractive surgery because of the potential for poor outcomes and the possibility that iatrogenic thinning of the cornea could lead to progression of the disease.     

Bilateral keratectasia after photorefractive keratectomy

PURPOSE: To report the clinical features, management, and outcome of a patient who developed bilateral ectasia after photorefractive keratectomy (PRK). METHODS: Case report of a 35-year-old man who underwent bilateral PRK. Preoperative uncorrected visual acuity was 20/200 in the right eye and 20/100 in the left eye. The patient's history was unremarkable and he denied a family history of ocular disorders. RESULTS: Two weeks after surgery, the patient presented with loss of visual acuity in both eyes. Uncorrected visual acuity was 20/80 in the right eye and 20/200 in the left eye. Objective refraction could not be obtained. Slit-lamp microscopy showed corneal thinning in both eyes. After examining the patient's family, his sister was found to have clinical and topographic keratoconus. CONCLUSIONS: Ectasia is a rare complication of PRK. We report the occurrence of bilateral ectasia after PRK in a patient with asymmetric bowtie topographies. We recommend that refractive surgery, even surface techniques such as PRK, be avoided in patients with a family history of keratoconus.     

角膜地形图引导的准分子激光手术提高RK术后视觉质量的研究

目的 评价角膜地形图引导的准分子激光个体化切削（T-CAT）手术治疗放射状角膜切开术（RK）后角膜表面不规则形态的临床疗效,并客观评估术后的视觉质量。方法 回顾性病例研究。选择第三军医大学大坪医院野战外科研究所眼科2013年3月至2015年11月RK术后角膜重度不规则行T-CAT治疗的患者23 例（38 眼）的临床资料,其中4眼行T-CAT引导的准分子激光角膜表面切削术（PRK）,其余34眼均行T-CAT引导的前弹力层下准分子激光角膜磨镶术（SBK）。行T-CAT引导的PRK患者于术前、术后1个月、3个月、6个月以及行T-CAT引导的SBK患者在术前,术后1 d、1周、1个月、3个月、6个月均行裸眼视力（UCVA）、最佳矫正视力（BCVA）、屈光状态、裂隙灯显微镜、角膜地形图、Pentacam眼前节分析及眼压等检查;其中22眼在术前和术后3个月行OQAS视觉质量客观检查。观察术中、术后并发症的发生情况,并对手术前后所有术眼的UCVA、BCVA、等效球镜度（SE）及其中22眼的视觉质量客观指标进行分析比较。术前与术后6个月的数据比较采用配对t检验。结果 术后6个月时38只术眼无一眼发生视力下降,BCVA为4.8～5.0（4.9±0.1）,UCVA为4.8～5.0（4.9±0.1）,实际与计划SE值各点围绕拟合线波动幅度<1.00 D,行T-CAT引导SBK的34眼术后1 d至术后6个月屈光状态的平均变化为（-0.51±1.10）D,术后1 d与术后6个月SE差值小于0.5 D的有20眼（53%）,小于1.0 D的有31眼（91%）。其中22眼术后6个月时的Holiday EKR Detail Report分布图宽度（D）、OQAS散射指数（OSI）和调制传递函数（MTF）截止频率（cutoff）值与术前比较,差异有统计学意义（t=-1.70、-2.45、3.24,P<0.05）。结论 T-CAT引导的准分子激光个性化手术对于RK术后角膜表面不规则形态的患者不仅具有良好的安全性、有效性、可预测性和稳定性,而且在提高患者视力的同时能够明显改善其视觉质量。     

Laser-assisted subepithelial keratectomy for myopia: two-year follow-up

PURPOSE: To assess and compare the clinical results (efficacy, safety, stability, and postoperative pain or discomfort) of laser-assisted subepithelial keratectomy (LASEK) and conventional photorefractive keratectomy (PRK) for the correction of low to moderate myopia. SETTING: Department of Ophthalmology, Masaryk University Hospital, Brno, Czech Republic. METHODS: A prospective comparative study was performed in 184 eyes of 92 patients who had surface excimer ablation for the correction of myopia. The preoperative mean spherical equivalent (MSE) was -4.65 diopters (D) +/- 3.14 (SD) (range -1.75 to -7.50 D). In each patient, LASEK was performed in 1 eye and PRK in the fellow eye by the same surgeon. The first eye treated and the surgical method used in the first eye were randomized. Both procedures were performed with the Nidek EC-5000 excimer laser using the same parameters and nomogram. The postoperative pain level, visual recovery, complications (haze), uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and refractive outcome were evaluated and compared. All eyes completed a 24-month follow-up. RESULTS: The postoperative MSE was -0.18 +/- 0.53 D in the PRK eyes and -0.33 +/- 0.46 D in the LASEK eyes. At 1 week, the mean UCVA was 0.64 +/- 0.21 and 0.87 +/- 0.23, respectively. No LASEK eye lost a line of BSCVA. There were no statistically significant differences between PRK and LASEK eyes in the safety and efficacy indices at 2 years. The mean pain level was significantly lower on days 1 to 3 in the LASEK eyes (P <.05). The mean corneal haze level was lower in the LASEK eyes (0.21) than in the PRK eyes (0.43) (P <.05). Seventy-nine patients preferred LASEK to PRK. CONCLUSIONS: Laser-assisted subepithelial keratectomy provided significantly quicker visual recovery, eliminated post-PRK pain, and reduced the haze level in eyes with low to moderate myopia compared with conventional PRK. It provided good visual and refractive outcomes. There were no serious complications.     

Intacs after laser in situ keratomileusis and photorefractive keratectomy

PURPOSE: To evaluate the efficacy of intrastromal corneal ring segments (Intacs, Addition Technology) for the correction of residual myopia after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). METHODS: In this prospective noncomparative case series, Intacs were implanted in 5 eyes (4 patients) that developed myopic regression after LASIK or PRK. Intacs were implanted a minimum of 11 months after the laser procedure. The technique was identical to the standard procedure for myopic unoperated eyes. The Intacs thickness was based on the amount of residual myopia. RESULTS: Postoperative results revealed a reduction in the residual myopia and the mean K-reading. No eye lost best corrected Snellen visual acuity. No intraoperative or postoperative complications occurred. CONCLUSIONS: Implantation of Intacs in eyes with myopic regression after LASIK and PRK resulted in a good refractive outcome and an improvement in uncorrected visual acuity.     

Effects of photorefractive keratectomy-induced defocus on emmetropization of infant rhesus monkeys

PURPOSE: To investigate whether photorefractive keratectomy (PRK) performed in infant primates can modify emmetropization and therefore could be used to study mechanisms of refractive error development. METHODS: Six healthy rhesus monkeys ranging in age from 2 to 3 months were randomly divided into two groups (n = 3 each). Anisometropia was induced in each animal by performing PRK on one eye. Hyperopic anisometropia was induced in group A monkeys by flattening the cornea of the right eye, whereas myopic anisometropia was produced in group B monkeys by steepening the cornea of the right eye. Corneal morphology and topography, refractive status, and axial growth were evaluated over a 5-month observation period. RESULTS: All the PRK-treated corneas were re-epithelialized and transparent within 3 days after surgery. Subsequently, all the surgically treated eyes exhibited interocular alterations in axial growth rate that were appropriate to compensate for the PRK-induced anisometropia. Specifically, vitreous chamber elongation rates were faster in the eyes with induced hyperopias than in their fellow eyes (0.63 +/- 0.05 mm vs. 0.40 +/- 0.09 mm), but slower in the eyes with induced myopia than in their fellow eyes (0.58 +/- 0.13 mm vs. 0.73 +/-0.10 mm). In some animals, the recovery from the induced anisometropia was facilitated by interocular differences in the rate of corneal flattening. However, the rates of corneal flattening in the treated eyes and their fellow eyes were not significantly different. CONCLUSIONS: PRK-induced defocus predictably alters axial growth rate and the normal course of emmetropization in developing eyes. Thus, PRK is a useful alternative to current methods used to impose experimental refractive errors in laboratory animals. These results also indicate that refractive surgery performed in childhood may affect normal growth of the eye, resulting in decreased predictability of future refractive status.     

Comparison of ocular higher-order aberrations and visual performance between photorefractive keratectomy and laser in situ keratomileusis for myopia

The purpose was to compare the ocular higher-order aberrations and the visual performance between photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Ocular aberrations and visual performance were measured after PRK in 26 eyes, after LASIK in 39 eyes, and in 29 normal myopic control eyes. Ocular aberrations were measured with a Hartmann-Shack aberrometer. Visual performance was evaluated with grating contrast sensitivity, high and low contrast visual acuity, and letter contrast sensitivity under full correction with spectacles. The results were that the root mean square (RMS) values of ocular higher-order aberrations after PRK or LASIK were significantly greater than that of normal controls for both 4-mm and 6-mm zones (PRK; 0.22 +/- 0.09 and 0.85 +/- 0.24 microm, LASIK; 0.20 +/- 0.06 and 0.82 +/- 0.24 microm, normal; 0.10 +/- 0.03 and 0.33 +/- 0.11 microm. P < 0.05 between PRK and normal, LASIK and normal, One Way ANOVA on Ranks). There were no significant differences between PRK and LASIK. The ocular higher-order aberrations increased in proportion with the attempted refractive correction by PRK and LASIK. The ocular higher-order aberrations correlated better with grating contrast sensitivity, low contrast visual acuity, and letter contrast sensitivity than with high contrast visual acuity. There was no difference among normal, PRK and LASIK in all the visual function tests, except between normal and PRK, or between normal and LASIK with letter contrast sensitivity. In conclusion, there was no difference in both ocular higher-order aberrations and visual performance between PRK and LASIK. The result suggests that surgeons can choose refractive procedures according to the corneal conditions or daily activities of patients.     

Cooling effect on excimer laser photorefractive keratectomy.

PURPOSE: To evaluate the effect of cooling on pain, corneal haze, and refractive outcome after excimer laser photorefractive keratectomy (PRK). SETTING: Tokyo Medical and Dental University Hospital, Tokyo, Japan. METHODS: The corneal surface was cooled before, during, and after laser ablation using a method called cooling PRK. Thirty-eighty highly myopic eyes of 38 patients whose spherical errors ranged from -8.00 to -18.75 diopters (D) were randomized into 2 groups: 16 eyes with conventional PRK and 22 eyes with cooling PRK. Postoperative pain was measured using the Visual Analogue Scale (VAS). Refraction, visual acuity, and complications were followed for up to 2 years. All data were analyzed and compared between groups to evaluate the cooling effect on PRK. RESULTS: One day postoperatively, patients in the cooling PRK group had significantly less pain (P < .01). At 3 months, the haze score in the cooling PRK group was significantly less than in the conventional PRK group (P < .01). The residual refractive error was not significantly different between the 2 groups until 2 years, when it was greater in the conventional PRK (mean -5.09 D +/- 2.11 [SD]) than the cooling PRK group (-4.64 +/- 2.27 D). Ten eyes (62.5%) in the conventional PRK group and 15 eyes (68.2%) in the cooling PRK group were within +/- 1.00 D of the intended refraction. There were no serious complications in the cooling PRK group. Two eyes in the conventional PRK group had severe corneal haze and lost 2 Snellen lines of best corrected visual acuity. CONCLUSION: Corneal cooling on PRK effectively reduced postoperative pain, corneal haze, and myopic regression.     

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.     

Effectiveness of cultured human keratinocyte onlays on epithelial healing and clinical outcome after photorefractive keratectomy

PURPOSE: To evaluate epithelial healing time, postoperative pain, corneal haze, and visual and refractive outcomes following the application of cultured sheets of human allogeneic epidermal keratinocyte (CEAK) onlays on the photorefractive keratectomy (PRK) -ablated corneal surface as dressing material. METHODS: In total, 204 eyes from 103 patients with myopia or myopic astigmatism were prospectively evaluated for 6 months after PRK. The ablated cornea was dressed in three different ways. Specifically, CEAK onlays were placed in 80 eyes (CEAK group), CEAK with amniotic membrane (AM) strips in 63 eyes (CEAK with AM group), and therapeutic contact lenses only in 61 eyes (control group). All eyes were covered with bandage contact lens after the operation. Contact lens removal time, intensity of postoperative pain score on postoperative day 2, corneal haze, Snellen visual acuity, and remaining refractive errors were measured. RESULTS: The mean contact lens removal time was shorter in the CEAK with AM group (1.84 +/- 0.72 days) compared to the control (2.77 +/- 1.59 days) and CEAK only (2.24 +/- 0.79 days) groups (P < .001). However, no significant differences were evident among the groups in terms of immediate postoperative pain, Snellen visual acuity, remaining refractive errors, and corneal haze at 6 months postoperative. CONCLUSIONS: The CEAK onlay with AM facilitates epithelial healing, and is thus a good candidate dressing material to decrease the epithelial healing time after PRK. However, this onlay method did not affect the intensity of postoperative pain or final visual outcomes after surgery.     

Photorefractive keratectomy in keratoconus suspects

PURPOSE: To compare the refractive outcome after photorefractive keratectomy (PRK) in keratoconus-suspect patients with that in patients with normal corneal topography. SETTING: Gimbel Eye Centre, Calgary, Alberta, Canada. METHOD: In a retrospective study, 3 patients (5 eyes) with unusually shaped corneal topography before surgery were selected as keratoconus suspects. Corneal topography (inferior-superior [I-S] value, central corneal power, and central power difference between both eyes), preoperative and 1 year postoperative refraction, and visual acuity in the keratoconus suspects were compared with those in a control group. RESULTS: The mean preoperative I-S value was 1.79 diopters (D) in the keratoconus-suspect eyes and 0.35 D in the control group eyes (P = .0001). The I-S value of individual corneas in the keratoconus suspects was more than 2 standard deviations above the mean in the control group except in 1 eye in which the steepened area was located in the central cornea. The central power difference between the eyes of this patient was 3.60 D, which was significantly higher than that in the control group. The refractive outcomes in the keratoconus suspects were comparable to those in the control group. CONCLUSION: In this study, the refractive outcomes after PRK in the keratoconus suspects and controls were comparable. However, further investigation with a larger sample and longer follow-up is needed.     

逆几何形特殊设计RGPCL矫正角膜屈光手术后的屈光不正

目的探讨后表面逆几何形特殊设计透气性硬性角膜接触镜（RGDRGPCL,近似角膜塑型镜设计）矫正准分子激光原位角膜磨镶术、准分子激光屈光性角膜切削术和放射状角膜切开术术后屈光不正的可行性和有效性。方法有针对性地选择角膜屈光手术后视力不良、残留明显屈光不正的29例患者（51眼）配戴RGDRGPCL,观察其配适状态、矫正视力、患者满意度、角膜形态变化、波前像差改变以及眼表健康状况。术后50眼球镜度-1．00—18．75D,散光度0．75～4．50D,裸眼视力3．0～4．8：1眼放射状角膜切开术后又受外伤致术后无晶状体眼,＋8．00D／＋6．00D×10°,视力3．0°所有病例戴框架镜矫正视力不满意,或存在屈光参差。同时选择30只配戴角膜塑型镜的中低度近视眼作为对照组。采用TomeyⅣ角膜地形图．显示角膜表面30个投照环,计算每6环的平均曲率,共5区,将角膜屈光手术后和角膜塑型术后两组角膜地形图中各区的平均曲率进行比较。评价戴镜3个月后的适配状态、患者满意度以及视力和波前像差的变化。对所得数据进行独立样本t检验。结果屈光手术后与近视眼配戴角膜塑型镜后,角膜地形图中各区参数相近[（39．24±2．09）DVS（39．27＋-1．23）D,（39．24＋-2．46）DVS（39．88＋-1．19）D,（40．34＋-2．48）DVS（41．39＋-1．43）D,（41．23＋-2．43）DUS（41．21±1．45）D．（41．02＋-2．36）DVS（40．50＋-0．79）D],两组之间各区参数的差异均无统计学意义（P〉0．05）。配戴RGDRGPCL后,35眼视力可达5．0或更高。配适状态基本良好,患者自觉清晰、舒适的满意度均较高,部分显示波前像差明显降低。戴镜期间末出现明显角、结膜并发症,部分长期戴镜后可出现角膜规则塑型效果。结论针对角膜屈光手术后视力低下．角膜中央区平坦而旁周边区陡峭的显著形变,而且利用普通框架眼镜和球面或非球面设计的RGPCL矫正困难的病例,配戴设计适宜的RGDRGPCL进行视力再矫正是一个合理、良好的选择．     

Randomized bilateral comparison of excimer laser in situ keratomileusis and photorefractive keratectomy for 2.50 to 8.00 diopters of myopia

OBJECTIVE: To compare effectiveness, safety, and stability of excimer laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for low-to-moderate myopia. DESIGN: Prospective, randomized, bilateral study. PARTICIPANTS: Thirty-three patients with a manifest refraction of -2.50 to -8.00 diopters (D) participated. INTERVENTION: For each patient, one eye received LASIK and the other received PRK. The first eye treated, and surgical method in the first eye, were randomized. Both eyes were treated by the same surgeon during the same operative session with a Summit Omnimed I laser (6-mm-diameter ablation) and a Chiron Automated Corneal Shaper. Follow-up was 90% at 1 and 2 years. RESULTS: At baseline, mean (+/-standard deviation) spherical equivalent manifest refraction was -4.80 +/- 1.60 D in LASIK-treated eyes and -4.70 +/- 1.50 D in PRK-treated eyes. At 1 day after surgery, 81% of patients (21 eyes) reported no pain in the LASIK-treated eye, whereas no patient (0%) reported being pain-free in the PRK-treated eye. At 3 to 4 days after surgery, 18 (80%) LASIK-treated eyes either improved or remained within 1 line of baseline spectacle-corrected visual acuity; only 10 (45%) PRK-treated eyes achieved this result. At 2 years after surgery, 18 (61%) LASIK- and 10 (36%) PRK-treated eyes achieved an uncorrected visual acuity of 20/20 or better, with no statistically significant difference in refractive outcome between the two techniques. Quantitative videokeratography showed more regularity after LASIK. Complications were similar in the two groups. Patients preferred LASIK by a margin of 2 to 1 at 1 year but showed no preference at 2 years. CONCLUSIONS: Using a 6-mm-diameter single-pass, large area ablation and an automated microkeratome to treat myopia of -2.50 to -8.00 D with 1.00 D or less astigmatism in 1994, the authors used LASIK to produce a higher percentage of eyes with an uncorrected visual acuity of 20/20 or better, more regular postoperative corneal topography, less postoperative pain, and more rapid recovery of baseline spectacle-corrected visual acuity than PRK. Both LASIK and PRK achieved successful correction of low-to-moderate myopia at 1 and 2 years after surgery.     

Photorefractive keratectomy retreatment after LASIK

PURPOSE: To study the results of late photorefractive keratectomy (PRK) in corneas originally subjected to LASIK. METHODS: Seven eyes of seven patients who had LASIK for myopia were retreated with PRK at least 2 years after LASIK. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, and haze were evaluated before and after LASIK and after retreatment by PRK. RESULTS: Photorefractive keratectomy retreatment improved BSCVA in six (86%) of seven eyes, and one (14%) eye showed no changes. None of the eyes lost lines of BSCVA. Five of seven eyes developed mild haze, which disappeared before the last postoperative follow-up. CONCLUSIONS: Photorefractive keratectomy retreatment performed at least 2 years after LASIK can improve visual acuity. We hypothesize that LASIK-induced corneal nerve damage disturbs corneal wound healing by increasing the tendency for development of haze.