Helena M C, Filatov V V, Johnston W T, Vidaurri-Leal J, Wilson S E, Talamo J H
Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, USA.
Cornea. 1997 Sep;16(5):571-9.
The corneal epithelium is generally removed before photoablation in photorefractive keratectomy (PRK) because laser transepithelial PRK may result in surface irregularity caused by variability in epithelial thickness and differing ablation rates between epithelium and stroma. We compared the effects of mechanical deepithelialization with chemical epithelial removal by using 50% ethanol on the corneal structure.
Fourteen rabbits underwent corneal deepithelialization by using a blade in the left eye and 24 h later in the right eye. Another 14 rabbits underwent corneal deepithelialization by using 50% ethanol solution. Half of the eyes treated with each technique underwent PRK after deepithelialization. Pachymetry was performed before and after each procedure on right eyes. Keratocyte and neutrophil densities were assessed by light microscopy.
Among non-laser-treatment groups, eyes that underwent mechanical deepithelialization had decreased corneal thickness (p = 0.001), increased keratocyte densities (p = 0.03), and no significant difference in neutrophil densities (p = 0.91) compared with chemically treated eyes 24 h after surgery. Among laser-treatment groups, eyes that underwent mechanical epithelial removal had increased keratocyte densities (p = 0.001), decreased corneal thickness (p = 0.03), and increased neutrophil densities (p = 0.03) 24 h after surgery compared with chemically treated eyes.
Deepithelialization with 50% ethanol causes more keratocyte loss with perhaps more corneal edema, but less stromal influx of neutrophils, than does a mechanical technique 24 h after PRK in a rabbit model. Corneal deepithelialization with dilute ethanol may be a viable option in PRK. However, further investigation into the safety of this technique is warranted before it can be widely applied clinically.
在准分子激光角膜切削术（PRK）中，通常在光消融前去除角膜上皮，因为激光经上皮PRK可能会因上皮厚度的变异性以及上皮与基质之间不同的消融速率而导致表面不规则。我们比较了使用50%乙醇进行化学上皮去除与机械性去上皮对角膜结构的影响。
14只兔子左眼使用刀片进行角膜去上皮，24小时后右眼进行同样操作。另外14只兔子使用50%乙醇溶液进行角膜去上皮。每种技术处理的眼睛中各有一半在去上皮后接受PRK。对右眼在每个手术前后进行角膜厚度测量。通过光学显微镜评估角膜细胞和中性粒细胞密度。
在非激光治疗组中，与化学处理的眼睛相比，接受机械性去上皮的眼睛在术后24小时角膜厚度降低（p = 0.001），角膜细胞密度增加（p = 0.03），中性粒细胞密度无显著差异（p = 0.91）。在激光治疗组中，与化学处理组相比，接受机械性上皮去除的眼睛在术后24小时角膜细胞密度增加（p = 0.001），角膜厚度降低（p = 0.03），中性粒细胞密度增加（p = 0.03）。
在兔模型中，PRK术后24小时，与机械技术相比，用50%乙醇去上皮导致更多的角膜细胞丢失，可能伴有更多的角膜水肿，但中性粒细胞向基质的浸润较少。用稀释乙醇进行角膜去上皮在PRK中可能是一个可行的选择。然而，在该技术能够广泛应用于临床之前，有必要对其安全性进行进一步研究。
