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.     

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     

高三尖杉酯碱对PRK后角膜浑浊的影响

目的　了解兔眼准分子激光角膜屈光切削术 (PRK)后 ,局部应用高三尖杉酯碱 (HHT)对角膜上皮下雾状浑浊(haze)抑制作用的效果。方法　将 3 0只健康家兔随机分为A、B、C 3组 ,每组 10只 ( 2 0眼 )。每组兔眼均用准分子激光屈光切削 -10 0DS。A组术后即以浸有 1mg/mLHHT的滤纸贴附于角膜切削区 5min ,用量约 0 1mL ,并用平衡盐液冲洗 ;B组自术后第 3天起双眼滴用 0 1mg/mLHHT ;C组为对照组 ,滴用生理盐水。分别观察 3组术后不同时期的眼部反应及角膜haze形成差别 ,并行组织病理学观察。结果　术后观察 3月 ,A组haze明显轻于B、C两组 (P <0 0 5 )。病理结果显示 ,A组角膜成纤维细胞增生程度明显轻于B、C两组 ,且未见明显毒副作用。结论　PRK术后应用浸有HHT的滤纸贴附切削区可抑制haze形成。     

Growth factor expression in corneal wound healing after excimer laser keratectomy.

PURPOSE: To develop a rabbit model of reproducible corneal haze after excimer laser keratectomy and to characterize expression of transforming growth factor beta (TGFbeta) and basic fibroblast growth factor (bFGF) in rabbit corneas during haze formation. METHODS: Seven rabbits underwent a 100 microm deep phototherapeutic keratectomy (PTK) in one eye and a 15-microm shallow PTK in the contralateral eye. Corneal haze was compared at 1-20 weeks after surgery. Subsequently, 16 rabbits underwent 100-microm PTK in one eye and 15-microm PTK in the contralateral eye. Four rabbits were killed at 1, 2, 3, and 4 weeks, respectively, after surgery. Immunohistochemistry was performed on the corneas to localize the expression of TGFbeta and bFGF. Control subjects were rabbits that underwent either epithelial debridement alone or no surgery. RESULTS: A 100-microm PTK resulted in significantly more corneal haze than a 15-microm PTK at every postoperative examination (p < 0.05). Both TGFbeta and bFGF were expressed in the scars at 1-4 weeks after deep and shallow excimer ablations. bFGF was expressed in the keratocytes of both treated and control corneas. Minimal TGFbeta was detected in the keratocytes of the control corneas, whereas prominent TGFbeta expression was noted in the keratocyte-like cells adjacent to the postkeratectomy scars. CONCLUSIONS: The 100-microm PTK ablation resulted in significantly more corneal scarring than the 15-microm PTK ablation. Even though there was no immunohistochemical difference in the pattern of TGFbeta and bFGF expression after deep and shallow ablations, there was an association between the expression of the growth factors and corneal scarring after excimer laser keratectomy.     

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.     

Corneal wound healing after excimer laser keratectomy

Excimer laser keratectomy is widely used to correct refractive errors. Several complications of excimer laser keratectomy are reported including corneal infection, regression, corneal haze formation, glare and halo. Most of the complications are closely related to the corneal stromal wound healing process. In order to perform the excimer laser keratectomy with minimum complications, we should understand the mechanism of the corneal stroma wound healing process. In addition, such knowledge will help us to regulate the corneal stromal wound healing process in the future. In the present article, we discuss the molecular mechanism of the corneal stromal wound healing process after excimer laser keratectomy and its regulation by anti-inflammatory agents.     

准分子激光角膜切削术与准分子激光原位角膜磨镶术角膜创口愈合的对比实验研究

比较准分子激光角膜切削术(photorefractive keratectomy,PRK)与准分子激光原位角膜磨镶术(1aser in situ keratomileusis,LASIK)后激光对角膜组织的切削效应及角膜的愈合情况,从组织学角度探讨角膜雾状混浊(Haze)及屈光度数回退的成因。方法24只新西兰白兔按预矫屈光度数随机分为-4.00 D组和-8.00 D组,每只兔右眼行PRK,左眼行LASIK。术后10d,1、3及6个月观察Haze情况并验光,每组随机处死3只兔取角膜行光镜、电镜及免疫组化检查,检测胶原Ⅲ、胶原Ⅳ、纤维连结蛋白(fibronectine,FN)及转化生长因子-β(transforming growth factor-β1,TGF-β2)的含量。结果行PRK术的右眼术后出现不同程度的Haze及屈光度数回退,其程度与预矫正屈光度数成正比。行LASIK术的左眼术后除少数角膜瓣周围半环形混浊外,手术区域角膜透明,屈光度数回退较右眼轻。-4.00 D组右眼与左眼术后屈光度数均稳定,-8.00 D组右眼较左眼屈光度数回退明显。右眼术后角膜愈合反应重,恢复慢。6个月时角膜基质仍处于修复阶段。左眼术后除形成角膜上皮栓及对应处基质轻度增生外,手术区域角膜瓣与基质床间界面清晰,无明显增生,角膜基质愈合反应轻、恢复快。术后所有兔眼角膜均有TGF-β1表达及活化,持续时间与角膜愈合时间一致。Haze及屈光度数回退组织学改变为：角膜上皮细胞增生,基底膜不成熟,前基质角膜细胞活化、增殖,新生胶原Ⅲ合成、排列紊乱,细胞外基质FN在角膜上皮下沉积。结论LASIK矫正近视尤其是高度近视优于PRK;角膜伤口愈合特别是基质愈合的反应程度,是。Haze及屈光度数回退的关键;TGF-β1是角膜愈合过程中重要调节因子,可通过介导角膜上皮一基质相互作用,调节胶原Ⅲ及FN的含量,参与瘢痕形成。     

Mitomycin C reduces corneal light scattering after excimer keratectomy

PURPOSE: To evaluate the effect of intraoperative mitomycin C (MMC) on corneal light scattering after excimer laser keratectomy. METHODS: Phototherapeutic keratectomy (PTK) was performed in 24 rabbit eyes. After 40-microm epithelial ablation, animals were divided into three groups. In group 1, filter paper discs soaked with MMC (group 1A, 0.5 mg/mL; group 1B, 0.25 mg/ml) were applied for 1 minute. In group 2, annular filter papers soaked with MMC (group 2A, 0.5 mg/mL; group 2B, 0.25 mg/mL) were applied for 1 minute. Controls received vehicle only (group 3). Six-millimeter diameter 100-microm deep PTK was performed. Corneal light scattering was measured weekly from 1 to 6 weeks, at 10 weeks, and at 8 and 13 months using a scatterometer. A corneal light scattering index (SI) ranging from 0 to 10 was calculated; SI of 1 represents normal scattering. RESULTS: A statistically significant decrease in mean SI was noted in group 2A (annular MMC 0.5 mg/mL; p<0.05) as compared with the control group at 2 weeks. At 10 weeks, SI approached baseline levels in group 2 and the control group but showed significant increase in group 1 (MMC disc; p < 0.05). At 8 and 13 months, SI showed no statistical differences between groups. CONCLUSIONS: Controlled application of 0.5 mg/mL MMC in the corneal midperiphery transiently reduces corneal light scattering after excimer keratectomy in this rabbit model.     

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     

准分子激光角膜上皮瓣下磨镶术和准分子激光屈光性角膜切削术后角膜上皮下雾状浑浊的对比观察

目的探讨准分子激光角膜上皮瓣下磨镶术（LASEK）手术和准分子激光屈光性角膜切削术（PRK）手术后角膜上皮下雾状浑浊（haze）的发生率。方法分别对120例（240眼）左右眼分别行LASEK和PRK手术,观察12个月,计算出低中度近视组（等于或低于-6.00D）和高度近视组（-6.00D以上）haze的发生率。结果低中度近视组和高度近视组LASEK手术后1,3,6,12个月haze的发生率均低于PRK手术后1,3,6,12个月haze的发生率,其中低中度近视组和高度近视组LASEK手术后1,3个月1级haze的发生率和PRK手术后1、3个月1级haze的发生率比较差异均有统计学意义（P〈0.05）,低中度近视组LASEK手术后12个月1级haze的发生率和PRK手术后12个月1级haze的发生率比较差异有统计学意义（P〈0.05）。结论 LASEK手术后haze形成情况显著好于PRK手术。     

Comparison of wound healing after photorefractive keratectomy and laser in situ keratomileusis in rabbits.

PURPOSE: To evaluate and compare the corneal wound-healing process after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). SETTING: Kangnam St. Mary's Hospital, Seoul, Korea. METHODS: Two surgical procedures, PRK with the VISX Star excimer laser and LASIK with a MicroTech microkeratome, were performed in 24 rabbit eyes. In the PRK group (n = 12 eyes), the rabbit cornea was treated with a 20 microns ablation. In the LASIK group (n = 12 eyes), a 20 microns laser ablation was performed after a 150 microns thick hinged corneal flap had been made. During both procedures, dichlorotriazinyl aminofluorescien (DTAF) dye was applied to the ablated stromal bed; in the LASIK group, the stromal side of the corneal flap was also stained with DTAF to differentiate regenerated collagen from normal stromal tissue. Corneal wound healing was evaluated postoperatively at 1, 4, 8, and 12 weeks using light, electron, and fluorescence microscopy. The amount of regenerated stromal tissue and the number of keratocytes were analyzed by an image-analysis system. RESULTS: In the PRK group, epithelial migration and regeneration were observed in the ablated area without any stromal regeneration 1 week postoperatively. However, newly regenerated, irregularly arranged stromal collagen, with epithelial hyperplasia in the ablated area, was observed 4 to 12 weeks postoperatively by light and fluorescence microscopy. The number of keratocytes in the surgical area was also increased. In ultrastructural observation using an electron microscope, the shape of keratocytes in the ablated area was changed, and the number of rough and smooth endoplasmic reticuli, ribosomes, mitochondria, and electron-dense vesicles in the cytoplasm were increased, suggesting that the cells were activated. In the LASIK group, there was no observed regenerated collagen between the corneal flap and the ablated stromal bed except in the wound margin. Lamellated, parallel collagen fibers in the cornealstroma were not disturbed. However, in the wound margin, corneal epithelial ingrowth between the flap and the stromal bed was observed, as was some regenerated stromal tissue. The amount of regenerated stromal tissue and the number of keratocytes in the wound area were statistically smaller than those in the PRK group (P < .05). Observation by electron microscopy showed no activated keratocytes, unlike in the PRK group. The collagen fibers in the wound area were parallel. CONCLUSION: Stromal wound healing in the LASIK group was minimal compared with that in the PRK group, except in the wound margin. These results may support the clinical findings of less corneal haze in the human cornea after LASIK.     

雷帕霉素对兔眼准分子激光角膜切削术后haze的影响

目的:探究调节自噬活性对兔眼准分子激光角膜切削术(PRK)术后角膜上皮下雾状混浊(haze)的影响.方法:新西兰大白兔64只行右眼PRK手术后,根据术后局部用药不同,随机分为4组:单纯手术组、14μmol/L二甲基亚砜组(DMSO)、50μmol/L雷帕霉素组、100μmol/L雷帕霉素组,每组16只.根据分组情况,术...     

羊膜移植对家兔PRK术后伤口愈合作用的研究

目的：观察羊膜对家兔PRK术后角膜伤口愈合反应的影响。方法：对30只家兔常规施行双眼PRK手术（－8．0D切削程序），即行羊膜移植，观察术后早期角膜切削区炎性细胞的浸润和角膜上皮愈合情况，晚期角膜成纤维细胞增生和上皮增生情况，观察haze并评分；早期测量角膜SOD活力和MDA含量，对结果进行统计学分析。结果：早期移植相炎性细胞的数目比对照组少，上皮愈合时间较短，晚期上皮增生较轻，晚期移植组成纤维细胞数目较少；移植组haze评分较低；早期移植组自由基反应产物MDA的含量较低，而SOD含量较高，差异均具有显著性。结论：羊膜能促进术后上皮愈合，减轻炎性反应和自由基反应，减少成纤维细胞增生，减轻haze的形成。     

准分子激光屈光性角膜切削术对角膜内皮细胞的影响

目的 探讨分析准分子激光屈光性角膜切削术（ＰＲＫ）治疗近视后对角膜内皮细胞的影响。方法 对１０１只眼ＰＲＫ术后者,用接触型镜面反光角人皮显微镜（Ｋｏｎａｎ ＳＰ－３５００型,日本）检测不同部位角膜内皮细胞,并统计分析其在不同度数范围内的平均细胞密度、细胞面积的变异系数和六角形细胞的百分率。结果 平均细胞密度在Ｃ组上降１０％,Ａ,Ｂ组的下降无统计学意义。细胞面积的变异系数及六角形细胞百分率均下降１０     

Natural history of corneal topography after excimer laser photorefractive keratectomy

Purpose

To investigate the natural history of corneal topography after excimer laser photorefractive keratectomy (PRK).

Design

A prospective, single center clinical study.

Participants

A total of 40 eyes of 34 patients with myopia were studied.

Intervention

Excimer laser photorefractive keratectomy and computer-assisted videokeratography were performed.

Main outcome measures

Preoperative, 1 week, and 1,2, and 3 months postoperative topography patterns were compared and changes assessed by averaging defined sectors of the ablation zone in individual maps to produce composite “average” topography maps.

Results

Corneal topography was generally not homogeneous at 1 week after PRK. By 3 months, there had been considerable smoothing of corneal contour. A general “central island” effect early in the postoperative period flattened over time. When right and left eyes were evaluated independently, a tendency toward a keyhole-semicircular pattern was seen on average; the maximum flattening was nasal and the least flattening was inferotemporal for both right and left eyes.

Conclusions

A tendency, on average, toward central island and keyhole-semicircular patterns is seen early in the postoperative course after PRK. Central islands tend to evolve into the keyhole-semicircular pattern, and the corneal topography in general after PRK tends to smooth considerably with time.     

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.     

羊膜移植对PRK后早期伤口愈合的影响

目的 探讨关膜移植激光角膜光学切除术（ＰＲＫ）后早期伤口愈合的影响。方法 对９只新西兰白兔双眼行ＰＲＫ,其中１眼术后立即行角膜表面羊膜移植,另眼为对照。于术后３、５、７ｄ取下角膜进行常规组织切片,光镜下观察角膜上皮和基质伤口愈合情况。结果术后３、５、７ｄ,羊膜移植组切削区中央角膜工明显小于对照组。术后３ｄ,羊膜移植组角有基质轻微水肿,有少量炎性细胞浸润,术后５ｄ全部消失。结论羊膜调节角膜伤口的仍