准分子激光角膜切削治疗高度近视的神经损伤与再生

AN EXPERIMENTAL STUDY ON CORNEAL NERVE DAMAGE AND REGENERATION AFTER EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY FOR HIGH MYOPIA

1目的 观察准分子激光屈光性角膜切削术 (PRK)治疗高度近视角膜神经损伤与再生的形态学变化 ,探讨角膜知觉减退与恢复的形态学基础及其与角膜雾状混浊的关系。 2方法 2 4只白兔左眼均按 - 15 .0 0 D行PRK治疗 ,右眼作为对照。于术后第 1,3,10 ,30 ,90 ,180天取角膜标本 ,光镜、电镜下观察角膜神经的损伤与再生情况。 3结果 术后 1～ 3d,切削区内深层神经干断端未见再生。术后第 10天 ,光镜下见上皮层神经纤维再生。术后第 30天 ,上皮层新生神经纤维密度增高 ,基质神经出芽再生。术后第 90天 ,新生神经纤维网丛密度高于正常 ,再生基质神经形态不规则。术后第 180天 ,角膜中央区神经再生过程尚未全部完成。术后 30～ 180 d,电镜示基质神经超微结构异常。 4结论 PRK治疗高度近视后 ,角膜基质神经再生较慢 ,使术后角膜知觉减退持续时间较长 ;切削了角膜深部基质神经干 ,可能是术后雾状混浊较重的原因之一。

Objective\ To observe the morphological changes and ultrastructural organization of corneal nerve damage and regeneration after excimer laser photorefractive keratectomy (PRK) for high myopia, and evaluate the morphological basis for the changes in corneal sensitivity and the correlation with haze.\ Methods\ 24 white rabbits were used.A one pass three zone technique was used to correct high myopia (-15.00D) in left eyes, and right eyes were used as control.Light micrography (acetylcholinesterase staining) and electron micrography were used to demonstrate morphological features in rabbit corneal nerves at 1 day, 3 days, 10 days,30 days,90 days and 180 days after PRK.\ Results\ At 1 or 3 days after PRK, the subepithelial nerve plexus and stromal nerve trunks didn't regenerete in high myopia group. At 10 days, some regenerating nerves within the treated area in epithelial and subepithelial layers were visualized in high myopia group.30 days after PRK the density of regenerative fibrils in epithelial layer in high myopia group was higher than that of normal and peaked at 90 days after PRK. In high myopia group 30 days after PRK, new regenerating stromal nerves sprouting was detected. Nerve regeneration had not completed in the central cornea in high myopia group at 180 days after PRK. Electron micrography showed abnormal ultrastructure of corneal nerves at 30,90 and 180 days after PRK, such as decrease of neurofilaments and swollen mitochondria.\ Conclusion\ PRK for high myopia can excise stromal nerve trunks. Stromal nerve regeneration is slower and ultrastructure of nerves is abnormal. The recovery of corneal sensitivity needs a long term. Haze in high myopia group after PRK being more intense may be related to the damage of corneal stromal nerve trunks. [