Excimer retreatment for scarring and regression after photorefractive keratectomy for myopia.

AIMS/BACKGROUND--Scarring associated with regression of refractive effect can occur after photorefractive keratectomy (PRK) for myopia. The experience of treating these complications is reported. METHODS--Eighteen of 285 eyes (6.3%) were retreated with the excimer laser. Age, sex, preoperative primary treatment keratometry, pre-primary treatment, pre-retreatment and post-retreatment spherical equivalents, best corrected and uncorrected visual acuities were recorded and analysed. RESULTS--At 6 months post-retreatment, the mean spherical equivalent was -2.07 dioptres (D) (SD 4.60 D). This spherical equivalent persisted in eyes followed for 12 months (-2.85D, SD 4.09 D). Nine of 18 eyes (50%) had uncorrected visual acuity of 6/12 (20/40) or better. If retreatment was undertaken within 6.5 months of the initial PRK, then scarring was likely to recur (p = 0.035). Nine of 10 eyes (90%) which had a retreatment spherical equivalent less than two thirds of their primary treatment spherical equivalent were within plus or minus 1.25D from emmetropia after retreatment. Four of 11 eyes (36%) followed for 12 months after retreatment rescarred with further regression. CONCLUSION--The data showed that eyes with scarring and regression of myopia should not be treated with PRK within 6 months of the initial procedure. Eyes with the highest percentage of regression towards their initial myopia tend to have a poor response to retreatment.     

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.     

高度近视眼准分子激光治疗前后角膜冷却对疗效的影响

目的探讨准分子激光角膜切削术（photorefractivekeratectomy,PRK）治疗高度近视眼前后角膜冷却对其疗效的影响。方法回顾性地对－6．00～－10．00D近视眼的63眼角膜冷却组和58眼对照组随访6mo,分析2组角膜haze表面形态统计值等的差异。结果角膜冷却组PRK术后角膜haze0．5～1级发生率6mo内明显比对照组低,PRK术后冷却组角膜愈合过程中对形态影响小。结论PRK治疗高度近视时对角膜表面的切削有一定的致热作用,该因素可能是导致术后角膜haze和形态恢复时间长的原因之一,PRK术前后角膜冷却对减少并发症有一定的作用。     

Changes in corneal topography after excimer laser photorefractive keratectomy for myopia

Computer-assisted analysis of corneal topography was performed in 17 normally sighted human eyes during the first year after excimer laser photorefractive keratectomy (PRK) for myopia. Laser ablation of the central cornea produced an optical zone with a smooth power transition to the peripheral cornea. Decentration of the ablation was noted in some eyes (less than 0.5 mm in 3 eyes, 0.5 to 1.0 mm in 10 eyes, 1 to 1.5 mm in 3 eyes, and 2.1 mm in 1 eye), suggesting that careful alignment of the laser beam is critical. Improved methods to align the ablation within the center of the entrance pupil are needed. In 12 of 17 eyes, the topographic pattern appeared to stabilize between 3 and 7 months after PRK. In the remaining five eyes, central ablation power changed by more than 0.5 diopters (D) between the 6- and 12-month examinations. Regression was more common and more pronounced in eyes with intended corrections more than 5 D, whereas the majority of eyes with intended corrections of 5 D or less showed good correspondence between the final change in central ablation power and the attempted correction. Two eyes had a loss of at least two lines of best spectacle-corrected visual acuity that was attributable to irregular astigmatism, decentration of the ablation, and/or corneal opacification.     

Changes in corneal topography after photorefractive keratectomy in myopia and their elimination

Topographic disorders in the cornea, regression of the refraction effect, and subepithelial corneal opacities are characteristic complications of photorefraction keratectomy. Disorders in corneal topography are early haze, asymmetrical haze, and optic zone decentration. Disorders in topography lead to decrease in visual acuity, numerous optic effects (monocular doubling, aureola, blurred image, etc.). Methods for these complications control by means of transepithelial ablation, which is carried out with due consideration for the data of topographic examinations under pseudofluorescence control, normalizes corneal topography in the majority of cases, notably increases visual acuity, decreases doubling, etc. No side effects were observed after transepithelial phototherapeutic keratectomy for a period of up to 12 months.     

Early corneal topography patterns after excimer laser photorefractive keratectomy for myopia

OBJECTIVES: We defined early patterns of corneal topography following excimer laser photorefractive keratectomy (PRK) with a Summit Apex laser without pretreatment software, investigated changes in patterns over time, and identified factors associated with different topography patterns. METHODS: Fifty-eight eyes of 39 myopic patients were studied. EyeSys videokeratography data were analyzed at 1 week and 1, 2, and 3 months after surgery and were classified using a standardized classification system. RESULTS: At 1 week, 4.3% (n = 2) of corneas showed a homogeneous topography, 0.0% showed a toric-with-axis configuration, 2.2% (n = 1) showed a toric-against-axis configuration, 8.7% (n = 4) showed an irregularly irregular topography, 17.4% (n = 8) showed a keyhole pattern, 23.9% (n = 11) showed a semicircular pattern, 41.3% (n = 19) showed a central island pattern, and 2.2% (n = 1) showed focal topographic variants. From 1 week to 1 month, 78.9% of maps changed; from 1 to 2 months, 33.3% of maps changed; and from 2 to 3 months, 40.0% of maps changed, generally to more regular patterns. The central island pattern, which predominated at 1 week, was not seen at 3 months; most had changed to the keyhole or semicircular pattern. An association was found between the central island pattern and irregularity of reflected rings on the video-image of the cornea (P = .05). CONCLUSIONS: The central island pattern is an early and usually transient topography pattern following PRK. Keyhole and semicircular patterns taken together were the most prevalent in the early postoperative period. In some cases, central islands may be a consequence of corneal epithelial irregularity, and the meridional orientation of the keyhole and semicircular patterns suggests an influence of epithelial healing over time.     

Correlation between refractive and corneal topographic changes after photorefractive keratectomy for myopia

PURPOSE: To compare videokeratographic and refractive data obtained before and after photorefractive keratectomy (PRK) for myopia. METHODS: Seventy-four eyes underwent PRK for myopia ranging from -2.50 to -17.00 D (mean, -7.76 +/- 3.17 D). All patients had videokeratography with the EyeSys instrument before, and 1 and 6 months after PRK, and the changes in three corneal power measurements (center of the ablation, apex, and effective refractive power) were compared with refractive changes. RESULTS: Changes obtained in the three corneal power measurements at 1 and 6 months were well correlated with manifest refraction (Pearson's coefficient ranged from 0.71 to 0.84). CONCLUSION: Power measurements obtained with corneal topography, as described above, are a reliable and objective method for the evaluation and follow-up of PRK, provided addition of an approximate 25% correcting factor.     

Late corneal scarring after photorefractive keratectomy concurrent with development of systemic lupus erythematosus

PURPOSE: To report a case of late-onset corneal haze following previous photorefractive keratectomy (PRK) concurrent with the development of systemic lupus erythematosus. METHODS: Single case report and review of medical literature. RESULTS: A 41-year-old woman underwent uneventful bilateral, non-simultaneous photorefractive keratectomy (PRK) with retreatment of the right eye after 1 year. Two months after retreatment, the patient presented with headaches and mental status changes and was diagnosed with systemic lupus erythematosus. Severe reticular corneal scarring developed in the right eye 1 year after retreatment. After the patient's disease was well controlled on a maintenance dose of hydroxychloroquine 200 mg twice a day, mechanical debridement was performed on the right cornea with a marked decrease in corneal haze and improved best spectacle-corrected vision. CONCLUSION: Patients who manifest with autoimmune disorders such as systemic lupus erythematosus may be at greater risk for developing dense, reticular corneal scars after PRK.     

PRK治疗高度近视的临床分析

目的探讨准分子激光角膜切削术对高度近视的疗效及其并发症。方法采用UV200型准分子激光机,对183例（330眼）—6．00D以上近视患者施行准分子激光角膜切削术,对随诊1a以上的患者进行观察。术前等值球面镜屈光度为—6．00～—26．00D（—10．27±—3．87D）,按屈光度分为3组：A组—600～—10．00D,199眼;B组—10．00～—15．00D,87眼;C组＞—15．00D,44眼。结果术后1a时裸眼视力＞0．5者276眼,占83．64％,M1．0者144眼,占43．64％;术后类固醇高眼压37眼,占11．21％;23眼（6．97％）的患眼有严重的角膜混浊,发生视网膜脱离3眼,眼底出血2眼。角膜曲率和中央角膜厚度在术后各时期无明显变化。结论PRK手术对高度近视是有效的．安全的。部分患者可获得良好的裸眼视力,大部分患者可明显减轻眼镜度数。     

Phototherapeutic keratectomy with mitomycin C for corneal haze following photorefractive keratectomy for myopia

PURPOSE: To evaluate the safety and efficacy of phototherapeutic keratectomy (PTK) with single application of mitomycin C for patients with severe corneal haze following photorefractive keratectomy (PRK) for high myopia. METHODS: Eight eyes of seven patients were treated with PTK and intraoperative topical application of mitomycin C (0.02%) for severe corneal haze (grade 3) following PRK for myopia. RESULTS: All patients' visual performance improved significantly. Mean preoperative visual acuity (20/200 for both UCVA and BSCVA) improved significantly to 20/33 (0.6) and 20/30 (0.7) for UCVA and BSCVA, respectively. Six eyes (85.7%) had improved UCVA to 20/40 or better and gained five or more lines of UCVA. The corneal haze score decreased from grade 3 initially (for all eyes prior to PTK and mitomycin C) to a final mean haze score of 0.3 (range 0 to 0.5). Mean final spherical equivalent refraction achieved was -1.30 +/- 1.60 D (range -3.75 to +1.25 D). One eye gained only three lines of visual acuity due to regression and residual haze. No adverse effects related to the use of mitomycin C were recorded. CONCLUSION: PTK with a single intraoperative application of mitomycin C was safe and effective in reducing corneal haze and improving visual acuity in patients with severe corneal haze following PRK.     

Anterior corneal surface after Nidek EC-5000 multipass and multizone photorefractive keratectomy for myopia

PURPOSE: To evaluate the correlation between the presence of irregularities in corneal ablation and the number of ablation zones with multipass and multizone photorefractive keratectomy (PRK). METHODS: The differential maps obtained from corneal topography performed before and 1 month after PRK in 62 eyes that had undergone PRK with the Nidek EC-5000 excimer laser were assessed for irregularities. PRK treatment ranged from -1.00 to -16.00 D (mean -5.25 +/- 2.72 D), and the number of zones ranged from one to five. RESULTS: Of 62 differential maps, 27 had an irregular pattern according to the Hersh classification, with a non-significant correlation with the number of treatment zones (chi2 = 5.09, P >.1). CONCLUSION: Our results suggest that corneal topography irregularities arising from multizone PRK were not related to the amount of treatment or to the number of ablation zones.     

准分子激光屈光性角膜切削术治疗高度近视探讨

目的探讨准分子激光角膜切削术(PRK)治疗高度近视的效果.方法应用VISX20/20B型准分子激光仪,采用多光区切削法治疗-15D以上超高度近视.术后随访19～38月,并对结果进行分析.结果术前最佳矫正视力0.69±0.19,术后裸眼视力0.61±0.11.术后3月左右角膜上皮下混浊(haze)明显,1年后最轻,该组haze平均(0.53±0.17)级,屈光度回退平均(3.15±1.56)D.结论对于角膜较薄,不适于准分子激光原位角膜磨削术(LASIK)的超高度近视患者,PRK的多光区切削方式仍不失为一种安全、有效且稳定性较好的方法.     

准分子激光治疗性切削联合屈光性切削治疗伴有角膜混浊的近视眼

目的　了解准分子激光治疗性切削 (PTK)联合屈光性切削 (PRK)治疗伴有角膜混浊近视眼的方法及疗效。方法　激光加刮除去除角膜上皮 ,PTK切削混浊角膜 ,直径为 7 0mm。PRK作近视切削 ,直径为 6 0mm。对于角膜不平者术中用黏弹剂填平后再行上皮去除及PTK。PTK切削深度为影响视力的角膜混浊深度减去PRK及上皮切削厚度。结果　 5 4例 (79只眼 )伴有角膜混浊的近视眼治疗后随访 1年以上 ,术前平均屈光度数为 (- 6 73± 4 17)D ,平均最佳矫正视力为 0 6 3,角膜混浊原因包括感染、机械外伤、化学烧伤、热烧伤、手术后瘢痕及其他原因。术中PTK联合PRK平均切削深度为 (12 4 6 3± 5 3 31) μm。术后 5 0只眼 (6 3 3% )切削区角膜上皮下雾状混浊 (Haze)≤Ⅰ级 ,6 9只眼(89 9% )裸眼视力等于或超过术前最佳矫正视力 ,平均为 0 74。角膜表面较术前光滑 ,散光减轻。结论　PTK联合PRK是治疗伴有角膜混浊近视眼的一种安全有效的方法。     

Changes in posterior corneal curvature after photorefractive keratectomy

PURPOSE: To determine whether myopic ablation by excimer laser photorefractive keratectomy (PRK) affects only the anterior curvature of the cornea or whether changes also occur in the posterior corneal curvature. SETTING: Department of Optometry and Neuroscience, UMIST, and Optimax Laser Eye Clinic, Manchester, United Kingdom. METHODS: Sixteen patients who presented for correction of myopia in 1 eye by excimer laser PRK were followed for 3 months. Only newly presenting patients were recruited, and the untreated eyes were used as controls. The patients were examined at the initial visit (0 week) and 6 and 12 weeks post-PRK. Measurements included Orbscan topography and pachymetry, autokeratometry, and ultrasound pachymetry. RESULTS: The mean patient age of the 8 men and 8 women was 29.6 years +/- 8.6 (SD) (range 20 to 47 years). The attempted mean spherical equivalent correction was between -1.73 and -6.43 diopters. Anterior corneal curvature and corneal thickness in the treated eyes changed systematically in relation to the amount of ablation. Posterior corneal curvature steepened in relation to the dioptric power treated. There were systematic differences between the pachymetry values obtained with the Orbscan and the ultrasound pachymeter. CONCLUSIONS: The results suggest that after myopic PRK, the thinner, ablated cornea may bulge forward slightly to steepen both anterior and posterior curvatures. This may account for the regression toward myopia that is typically found in the first few days posttreatment. The forward bulging is similar to the corneal relaxation effects observed after radial keratotomy.     

Angle kappa changes after photorefractive keratectomy for myopia

The goal of this study was to compare differences in the mean angle kappa and its intercepts before and after photorefractive keratectomy (PRK) for myopia. In a prospective controlled study, myopic patients were treated with aspheric wavefront-guided (personalized) PRK with a Bausch & Lomb Technolas 217z excimer laser. The manifest refraction, visual acuity, and angle kappa were evaluated preoperatively and at 1 and 6 months postoperatively. The same operator performed all angle kappa measurements using Orbscan IIz. A total of 48 cases (96 eyes, 68.75 % female) with a mean age of 26.70 ± 4.89 years (18–34 years) were treated. The preoperative and postoperative mean angle kappa values were not significantly different (4.97 ± 1.24 vs 4.99 ± 1.10 at 6 months). The average horizontal distance (x-intercept) between the visual axis and pupillary axis intersection on the corneal surface measured before surgery (?0.562 ± 0.074 mm) did not significantly differ from the values measured at 1 and 6 months after surgery (?0.559 ± 0.048 and ?0.554 ± 0.055 mm, respectively). Similarly, the average vertical distance (y-intercept) values did not differ before and at 1 and 6 months after surgery (0.156 ± 0.225, 0.142 ± 0.040, and 0.149 ± 0.33 mm, respectively). No differences in the angle kappa or its corneal intercepts were observed between pre- and post-PRK. This finding implies that PRK does not change the corneal vertex locations.