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。     

Effect of mitomycin C on the corneal endothelium when used for corneal subepithelial haze prophylaxis following photorefractive keratectomy

PURPOSE: To evaluate the potential effect of topical mitomycin C (MMC) on the corneal endothelium of myopic patients undergoing photorefractive keratectomy (PRK). METHODS: Sixteen eyes with a planned ablation depth >75 microm underwent PRK followed by 0.02% MMC applied for 12 seconds using a methylcellulose sponge. Endothelial specular microscopy was performed with the Keeler-Konan specular photomicroscope in 16 eyes before and at least 1 year after surgery. Mean follow-up was 18 months (range: 12 to 24 months). Mean cell density, coefficient of variation of mean cell area, and percentage of hexagonal cells were measured and calculated using computerized morphometric analysis. RESULTS: Mean endothelial cell densities before and after surgery were 2882 +/- 783 cells/mm2 (range: 1511 to 4022 cells/mm2) and 2867 +/- 588 cells/mm2 (range: 1638 to 3881 cells/mm2), respectively (P > .05). Mean coefficient of variation before and after surgery was 0.30 +/- 0.07 (range: 0.23 to 0.49) and 0.26 +/- 0.04 (range: 0.22 to 0.33), respectively (P=.06). Mean percentage of hexagonal cells before and after surgery was 61% +/- 6.8% (range: 47% to 70%) and 66% +/- 6.7% (range: 54% to 75%), respectively. CONCLUSIONS: Administration of MMC for haze prophylaxis following PRK did not have a significant effect on quantitative endothelial cell density or qualitative morphometric parameters in this study.     

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.     

Dry eye after photorefractive keratectomy with adjuvant mitomycin C

PURPOSE: To report a patient with dry eye after bilateral photorefractive keratectomy (PRK) with mitomycin C treatment in one eye. METHODS: A 29-year-old woman underwent PRK for moderate myopia. The left eye was randomly assigned and intraoperative topical mitomycin C was administered. The right (control) eye was treated with intraoperative corticosteroid only. RESULTS: The patient developed dry eye symptoms and superficial punctuate keratopathy in the eye treated with mitomycin C. Fifteen months after surgery no improvement was noted. CONCLUSIONS: Photorefractive keratectomy with mitomycin C treatment could induce or exacerbate dry eye.     

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.     

Ascorbate prophylaxis for corneal haze after photorefractive keratectomy

PURPOSE: To evaluate whether prophylactic systemic ascorbic acid influences the average level of haze and the incidence of late onset corneal haze after photorefractive keratectomy (PRK). METHODS: Two consecutive groups of eyes treated with PRK for myopia with or without astigmatism were retrospectively compared. The patients had been treated similarly, with the exception that systemic ascorbate had been supplied orally in one of the groups. Haze intensity was quantified on a scale from 0 (clear cornea) to 4 (anterior chamber not visible). The diagnostic criterion for late onset corneal haze was a haze grade 2 or higher, occurring 4 to 12 months after surgery. RESULTS: One week, 1, 3, 6, and 12 months after surgery, the group without ascorbate (314 eyes) showed haze of average levels 0.61, 0.51, 0.50, 0.32, 0.10, respectively, and the group with ascorbate (201 eyes) showed haze of average levels 0.38, 0.18, 0.16, 0.09, 0.06, respectively. Comparison of the respective values showed a statistically significant difference between the two groups (P<.01) at 1 week, 1, 3, and 6 months. Late onset corneal haze was observed in 11 eyes in the group without ascorbate, and none was observed in the group with ascorbate (P<.02). CONCLUSION: This retrospective nonrandomized clinical study suggests that oral ascorbic acid supplementation may have a prophylactic effect against haze development after PRK. However, routine prophylactic use of ascorbate can be recommended only after a randomized, prospective clinical trial substantiates its efficacy.     

Bilateral corneal infiltrates after excimer laser photorefractive keratectomy

A 26-year-old man developed painless inferior subepithelial infiltrates away from the site of ablation in both eyes after excimer laser photorefractive keratectomy (PRK) for myopia. Clinical characteristics of the corneal infiltrates resembled staphylococcal-immune infiltrates. The condition responded to treatment with topical diluted steroids and antibiotics. There was no residual corneal scarring. The infiltrates did not affect the refractive outcome of the surgery. Recognition of this rare entity will help clinicians avoid aggressive investigative and treatment modalities that can affect the results of PRK.     

准分子激光屈光性角膜切削术后角膜地形图的变化

目的探讨准分子激光屈光性角膜切削术（ＰＲＫ）后角膜表面形态和屈光力变化。方法ＴｏｍｅｙＴＭＳ２ＴＭ角膜地形图检查１２４只近视眼ＰＲＫ术前、术后１、６月和１年统计值的变化。结果ＰＲＫ术后眼绝对等级角膜地形图见梯度明显的蓝色低屈光带。ＳＲＩ和ＳＡＩ术后１月时比术前和术后６月、１年时高，ＩＡＩ术前后无变化。近视眼治疗等值球镜屈光度分别与ＳＲＩ、ＳＡＩ和ＩＡＩ的相关系数为０．７６６、０．４６１和－０．１０５。结论ＰＲＫ术后角膜屈光力稳定性较好，对角膜表面规则性和对称性早期有影响，逐渐恢复正常。ＰＲＫ角膜切削区带越多，对角膜表面形态影响越大。     

准分子激光角膜切削术后角膜混浊的初步临床观察

对我院1995年2月-6月397例（738眼）近视患者行准分子激光角膜切削术治疗，随访6－10月的126例（239眼）进行观察发现，术后角膜混浊2级以上影响视力恢复盲占3．77%。角膜混浊的发生与性别、年龄、屈光度和切削深度无关，可能与屈光回退，末使用皮质类固醇和个体差异有关。在术后随访6－10月，绝大多数角膜混浊逐渐减轻。本组病例PRK手术效果初步观察表明，这是治疗近视的一种比较安全有效的方法。     

准分子激光角膜切削术后角膜地形图的分析

目的：准分子激光角膜切削术（ＰＲＫ）后角膜性状和视力质量和研究。方法：对２３例（３８只眼）近视患者于术后１、３、６个月进行角膜地形图随访。结果：ＰＲＫ术后角膜表面的球面性状发生一定改变。随着时间推移，角膜表面规则指数（ＳＲＩ）和表面不规则指数（ＳＡＩ）均逐渐降低，角膜变得中平滑。模拟角计数数表现一定的回退。术后６个月时，角膜地形图主要表现为四种形态；圆形或椭圆形、哑铃形、半环形、中央小岛形、有珞种     

Changes in Descemet's membrane and endothelium after photorefractive keratectomy in rabbits

OBJECTIVE: To investigate the effects of epithelial abrasion on the corneal endothelium and Descemet's membrane and to compare the changes with those after eximer laser photoablation of the cornea. METHODS: The animal models of corneal epithelial abrasion and excimer laser photoablation of the cornea were performed on the rabbit eyes. The central epithelial abrasion, 7 mm in diameter, was created by mechanical removal of the epithelium, and the specimens were examined at 24 hours, 7 days, 14 days and 30 days by transmission and scanning electron microscopy. Corneas that were photoablated by an excimer laser and non-treated normal corneas were investigated as controls. RESULTS: (1) Corneas with the epithelium removal showed massive enlargement of the mitochondria in the endothelium and exhibited a layer of electron-dense fibrillogranular material that had migrated forward through the Descemet's membrane. These alterations were similar to the changes observed after photoablation of the cornea by an excimer laser. (2) The edema and pathologic changes of corneal endothelium in eyes with denuded epithelium alone were similar to that observed after photoablation of the cornea by an excimer laser. CONCLUSION: The extrusion of electron-dense material in the Descemet's membrane observed after excimer laser ablation destruction of the epithelial integrity.     

Phototherapeutic keratectomy of a corneal scar due to presumed infection after photorefractive keratectomy

This case involves a 25-year-old patient who suffered from corneal ulceration several days after photorefractive keratectomy (PRK). A central scar developed, resulting in discomfort and reduction in visual acuity. Four months later, the scar was treated by phototherapeutic keratectomy (PTK) (25 microns depth, 5 mm ablation zone). Some scar tissue was left, but it cleared slowly and steadily over the next few years. The induced hyperopia decreased from 5.00 to 1.37 diopters spherical equivalent within 28 months postoperatively. Best corrected visual acuity increased from 20/60 preoperatively to 20/20 at 28 months postoperatively. Surgeons can encourage patients with postinfectious scars after PRK to try at least 1 PTK treatment.     

Intraocular lens power calculations using corneal topography after photorefractive keratectomy

PURPOSE: To report the preoperative and postoperative palpebral fissure width in eyes undergoing laser in situ keratomileusis.METHODS: In a prospective study, 165 consecutive eyes of 87 patients (41 men and 46 women with a mean +/- standard deviation age of 32.9 (+/-9.5) years) had laser in situ keratomileusis using a Summit (Waltham, MA) APEX PLUS excimer laser and a Moria (Antony, France) LSK microkeratome. The width of palpebral fissure was measured preoperatively, 3 months or 6 months after laser in situ keratomileusis. Patients were classified into three groups as follows: hard contact lens users group (n = 61), soft contact lens users group (n = 63), and non-contact lens users group (n = 41).RESULTS: The average width of palpebral fissure increased after laser in situ keratomileusis in all three groups. The hard contact lens users group increased from 7.6 (+/-1.6) mm to 8.7 (+/-1.2) mm (P <.0001) and non-contact lens users group increased from 7.7 (+/-1.9) mm to 8.9 (+/-1.9) mm (P <.0001).CONCLUSION: These results suggest that laser in situ keratomileusis may be associated with an increase in the width of the palpebral fissure.     

Scanning laser polarimetry in corneal topographic changes after photorefractive keratectomy

Purpose: To examine whether, or not, corneal topographic changes after excimer laser photorefractive keratectomy (PRK) for myopia and myopic astigmatism have any influence on measurements of the retinal nerve fiber layer (NFL) with scanning laser polarimetry. Methods: Retinal NFL thicknesses were determined by scanning laser polarimetry in 17 eyes of 13 patients with myopia and myopic astigmatism before and after PRK. Total ablation depth ranged from 26 to 71 μm. We used the relative ratios for superior and inferior NFL thicknesses which were calculated by dividing the NFL values of respective regions by the nasal value. Results: The mean superior NFL ratio measured was 3.02 ± 0.92 preoperatively, and 3.00 ± 0.76 postoperatively. The mean inferior NFL ratio was 2.95±0.75 preoperatively, and 2.99±0.66 postoperatively. There was no statistically significant difference between preoperative and postoperative NFL measurements (Wilcoxon signed rank test, p > 0.05). Conclusions: Corneal topographic changes after PRK have no significant influence on NFL measurements by scanning laser polarimetry. Our results suggest that scanning laser polarimetry can be used as a reliable method for retinal NFL thickness measurements even after excimer laser PRK. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of topical tranilast on corneal haze after photorefractive keratectomy

PURPOSE: To determine whether topical tranilast might reduce corneal haze through suppression of transforming growth factor (TGF)-beta1 synthesis in keratocyte after photorefractive keratectomy. SETTING: Department of Ophthalmology, Korea University College of Medicine, Seoul, Republic of Korea. METHODS: Photorefractive keratectomy was performed on 48 eyes of 28 white rabbits and 24 eyes in a tranilast group were treated with tranilast solution, and the other 24 eyes in control group were treated with saline after laser ablation. The grades of corneal haze at 1, 2, 4, and 8 weeks after surgery were evaluated in 10 eyes of each group for comparison. Immunohistochemistry was performed on 10 eyes of each group, and Western blot analysis was done on 4 eyes of each group for studying TGF-beta1 expression at postoperative day 7. RESULTS: There was no statistically significant difference in corneal haze between 2 groups from week 1 to week 4 after surgery, but a significant difference was found at week 8 after photorefractive keratectomy (P=.02). The mean number of keratocytes that expressed TGF-beta1 in the tranilast group was 58.3 (+/-17.2), which showed significant difference, compared with that of the control group, 104.5 (+/-23.0) (P<.01). Western blot analysis also revealed that the amount of TGF-beta1 in tranilast group was slightly less than the control group. CONCLUSIONS: Topical tranilast could reduce corneal haze by suppressing TGF-beta1 expression in keratocytes after photorefractive keratectomy.     

准分子激光屈光性角膜切削术后10年角膜内皮细胞的观察

ObjectiveTo evaluate and determine the long-term effects of photorefractive keratectomy （PRK） on corneal endothelial cell density and morphology, and investigate their correlation with surgically designed parameters such as ablation depth and laser scan time. MethodsIn this retrospective study, 24 patients （44 eyes） who underwent PRK 10 years earlier and 45 normal eyes of 25 cases without any ophthalmologic surgery were enrolled in this study as the PRK group and the control group, respectively. Noncontact specular microscopy （Topcon, SP3000P, Japan） was used to measure central corneal endothelial cell density and morphology. A Pearson correlation was used to analyze the relationship between corneal endothelial cell density and morphology, and surgically designed parameters. The PRK group was divided into 3 subgroups based on the depth of tissue ablation： low ablation group （ablation depth <60 μm）, moderate ablation group （ablation depth： 60~90 μm） and high ablation group （ablation depth >90 μm）. The differences in corneal endothelial cell density and morphology between these 3 groups and the control group were analyzed. Data were analyzed using independent samples t test, Pearson correlation, ANOVA. ResultsThe differences in average endothelial cell area, endothelial cell density, coefficient of variation of the endothelial cell area and percentage of hexagonal cells between the PRK group and control group were not statistically significant （t=-1.390, 1.323, 0.569, 0.788, P>0.05）. However, there were statistically significant correlations between average endothelial cell area and endothelial cell density and manifest refraction spherical equivalent （MRSE） （r=-0.424, 0.420, P＜0.01）. The 2 parameters were also significantly correlated with attempted ablation depth （r=0.391, -0.388, P＜0.01）. The differences in average endothelial cell area, endothelial cell density, coefficient of variation of the endothelial cell area and percentage of hexagonal cells between the low ablation group, moderate ablation group, high ablation group and control group were not statistically significant （F=2.195, 1.961, 0.817, 1.529, P>0.05）. ConclusionCompared to normal eyes, no significantly abnormal change in central corneal endothelial cell density or morphology was observed 10 years after PRK. MRSE and attempted ablation depth may have an effect on the average endothelial cell area and endothelial cell density.     

PRK术后角膜上皮下雾状混浊的相关因素分析

为探讨准分子激光角膜切削术（ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｋｅｒａｔｅｃｔｏｍｙ，ＰＲＫ）后角膜上皮下雾状混浊（ｈａｚｅ）的原因及影响因素，对ＰＲＫ后６个月时屈光度在－１．００～－１８．５０Ｄ的３１６例（６１５只眼）近视眼的ｈａｚｅ相关因素进行观察和比较。结果：ＰＲＫ后６个月时ｈａｚｅ发生率为４４．７％，１级或以上ｈａｚｅ为１３．３％。ｈａｚｅ的发生率及密度随屈光度增高而增加（Ｐ＜０．０００１），也随切削深度的增加而增加（Ｐ＜０．０００１），术前非接触眼压超过１８ｍｍＨｇ者，ｈａｚｅ的发生率和密度增加（Ｐ＜０．００５），男性较易发生ｈａｚｅ（Ｐ＝０．０００１），与年龄呈负相关（Ｐ＜０．０５）。而角膜厚度、术前戴用接触镜及散光对ｈａｚｅ的影响不显著。结论：高度近视（＞－６．０Ｄ）和过深的切削（＞８０μｍ）是引起ｈａｚｅ的主要原因。术前眼压偏高、年龄偏低对ｈａｚｅ也有明显影响。对ＰＲＫ治疗高度近视应持审