Department of Ophthalmology，The Second Affiliated Hospital of NanHua University，Hengyang421001.
     
　　【Abstract】 Objective To evaluate the efficacy，predictability and safety of laser in-situ keratomileusis（LASIK）and photorefractive keratectomy（PRK）for the correction of moderate and high hyperopia.Methods We chose20white rabbits as animal model.The rabbits were divided into two groups according to operation method.Operations were performed with Mulit Scan KERATOM excimer laser.The subjects were randomly divided into two groups.One group was preformed LASIK，the other PRK.Surgery was performed on the right eye of the rabbit to attempt a correction of+5.00D，and the left eye of the rabbit to attempt a correction of+8.00D.The rabbits were examined with videokerˉatoscope and slit-lamp microscope preoperation and in3days，2weeks，1months，2months，3months，6months postopˉeration respectively.At each time of the postoperation examination，one rabbit of each group was killed randomly，the both corneas were removed for histopathological observation of transmission electron microscopy and light microscopy.Results No complication was observed.At the6th month postoperation，the increase of the LASIK group which to attempt+5.00D and+8.00D was+4.58±0.67D and+8.59±0.83D respectively，the PRK group was+4.56±0.80D and+7.33±0.98D respectively.Compared with peroperation，the central astigmatism increased.The statistical significant regression（P<0.05）of both groups occurred during the period of3days to1months postoperation.At the6th month，there was no statistical significant regression（P>0.05）of both groups.Comparing PRK group with LASIK group，there no statistical difference in the range of+5.00D and there was statistical difference in the range of+8.00D.The histopathological investigations showed that the healing response of LASIK group was similar to that of PRK group.Conˉclusion Both LASIK and PRK are safe.LASIK is superior to PRK in efficacy and predictability in treating high hyperˉmetropia.
     
　　Key words hyperopia laser-in situ keratomileusis photorefractive keratectomy histopathological observation 

　　近年来，准分子激光治疗远视已在临床上得到了应用，由于角膜的形态结构及生物学特点，治疗远视的可预测性和稳定性仍有不足。LASIK手术是近几年来广泛开展的术式，它保留角膜上皮层和前弹力层，具有许多其它屈光性手术无法比拟的优点 ［1］  ，国内外对其临床研究的报道较多，而对于LASIK的实验研究报道相对较少。兔眼的结构与人眼的结构相似，故我们应用LASIK在兔眼角膜基质的旁中央区切削治疗高中度远视的实验研究并与传统的PRK手术进行了比较，同时进行光学和电镜的病理学观察，对LASIK手术的效果、安全性和可预测性进行全面的评估。报告如下。

　　1 材料与方法

    1.1 动物模型的建立 选用出生日期相近的健康纯种新西兰大白兔20只，雌雄不限，体重在2.5～3.0kg。按随机的原则将20只兔子分为LASIK和PRK两手术组，根据预期的远视矫正度数的不同，设计每组兔右眼为+5.00D，左眼为+8.00D，应用LASIK和PRK进行预期矫正度的激光切削。

    1.2 术前检查 全部实验兔眼术前通过裂隙灯检查，以排除眼部病变，并采用角膜地形图检测进行记录及分析。

    1.3 手术方法 采用德国视明公司生产的Mulit Scan KERATOM舒荣 TM  多光束智能扫描准分子激光系统及法国Moria公司生产的LSK-One气动板层角膜成形刀，使用激光制造厂家提供的治疗远视的软件。术前经耳静脉注射3%戊巴比妥钠进行全身麻醉（约1ml/kg体重），常规消毒铺巾，开睑器开睑，颞侧角膜上皮划痕作角膜瓣定位标记，确定角膜中心，放置1号负压环固定眼球，使眼压达65mmHg（1mmHg=0.133kPa），启动气动式板层成形刀，做直径8.0～9.0mm带蒂角膜瓣，蒂位于鼻侧，蒂的宽度约30°，角膜瓣厚度130μm。翻转角膜瓣，将术眼参数输入电脑，确定角膜中心后开启准分子激光在基质层行激光切削，每组兔右眼预期矫正度数为+5.00D，切削直径参数5.5mm，切削深度为74μm，每组兔左眼预期矫正度数为+8.00D，作分区域切削，切削直径参数5.5～6.5mm，切削深度为64～152μm。激光切削后将角膜瓣复位，以BSS在瓣下冲洗，清除杂质，然后将角膜瓣仔细对位、吸干。去除开睑器，检查确认角膜瓣无移位，滴泰利必妥眼液。

    1.4 术后的处理 术后LASIK组泰利必妥滴眼，每日4次，连续1周;氟美瞳眼液滴眼，第1周每日4次，以后每周递减1次，共滴4周停药。PRK组泰利必妥滴眼，每日4次，连续1个月;氟美瞳眼液滴眼，第1个月每日4次，釉后每个月递减1次，共滴3个月停药。

    1.5 术后观察 术后第3天、2周、1个月、2个月、3个月、6个月定期作角膜地形图及裂隙灯检查，采用美国FDA分级标准进行Haze分级。并随机选1只 兔子，用3%戊巴比妥钠全身麻醉后摘除眼球，完整剪下角膜平分两半，一半无水酒精固定24h，石蜡包理、切片等，常规苏木素-伊红染色进行光镜检查;一半用2.5%的戊二醛固定，送电镜室处理，进行透射电镜检查。

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