【作者】 徐建刚；

【导师】 刘汉强；

【作者基本信息】 中国医科大学 ， 眼科学， 2004， 硕士

【摘要】 前言 准分子激光原位角膜磨镶术(laser in situ keratomileusis，LASIK)是近年来发展最快的矫治屈光不正方法，其主要过程包括负压吸引术眼，微型角膜板层刀做一直径为9.5mm的角膜瓣，然后掀开瓣在其下的基质床上进行激光切削，最后把角膜瓣回复原位等一系列操作。 随着对LASIK基础和临床研究的深入，发现由于角膜瓣制作不精确，术中术后有一些并发症的发生，例如术中角膜瓣过薄形成薄瓣，游离瓣和不完全瓣，角膜瓣过厚可能导致术后角膜膨隆，屈光回退等。因而研究角膜瓣厚度的影响因素对预防术中术后并发症，提高手术疗效有重要意义。 在角膜瓣的切削过程，其厚度主要由微型角膜刀固定板与刀刃之间的距离决定，但有研究表明多种因素可影响角膜瓣的厚度，这些因素包括角膜厚度和弯曲程度，负压吸引时的负压值，眼内压，刀的旋转和切削速度，手术室的湿度等。本实验主要从负压吸引时间角度探讨其对角膜瓣厚度的影响，从而达到减少角膜瓣制作误差和LASIK术中术后并发症的目的。 材料和方法 一实验材料:采少山离体猪眼45只(离体4小时以内，4摄氏度湿房保存，实验前裂隙灯检查除外角膜上皮损伤的)，Moria MZ型微型角膜板层刀，非接触眼压计，角膜验光仪，角膜超声测厚仪，裂隙灯，秒表，镀铬游标卡尺等 二.实验方法:每个猪眼采用1毫升注射器针头通过视神经处注入生理盐水，使眼压达到20一25mmHg。测角膜厚度及K值并分为3组，10秒组(15只眼)，20秒红I(15只11民)，30秒组(xs只眼)，然后模仿人右眼，分别吸引10秒，20秒和30秒并做角膜瓣，测量角膜中央剩余厚度，由术前角膜厚度减去剩余厚度得到角膜瓣厚度，并测量角膜瓣直径。 三.统计学分析:3组.间的角膜厚度，角膜曲率和角膜瓣的厚度和直径比较均采用SPSS 10.0统计软件进行t检验分析。 10秒组，20秒组和30秒组的平均角膜瓣厚度分别是147.2士15.96um，x57.33士24.85um，267.6士22.37um.lo秒组和30秒组的平均角膜瓣厚度比较有统计学意义(P二0.008).10秒组，20秒组和30秒组的平均角膜瓣直径大小分别是8.668士o.16olmm，8.8627士o.2534mm和9.06士o.223smm，3组间比较均有统计学意义.讨论 LASIK术中角膜瓣厚度受多种因素影响，国内外已有一些报道，但从负压吸引时间角度探讨的研究很少。不同负压吸引时间导致角膜瓣厚度变化的一可能原因是眼球有一定顺应性，连续吸弓}能改变角膜和眼球的形状，使眼轴变一长突出于切削一平而，导致角膜瓣的厚度变化.同时伴随角膜瓣直径大小的变化. LASIK术’二卜负压吸引时间对角膜瓣厚度的影响有一定临床意义，通过控制吸引时间可减少切削过厚角膜瓣的危险性，这对保持角膜基质床的厚度大于250um有帮助，从而减少术后屈光回退和角膜膨隆的发生率。产生负压吸引时间过长的主要原因是手术医师技术不够熟练，这说明LAsIK手术医师提高业务水平对减少术中术后并发症有垂要意义.结论1.LASIK术中负压吸引时间是角膜瓣厚度的影响因素之一。2.LASIK术中随着负压吸引时间的延长，角膜瓣厚度逐渐增加。更多还原

【Abstract】 PrefaceLaser in situ keratomileusis(LASIK) is one of the most quickly developing methods to correct the refraction error in rescent years.The techniques include negative pressure suction and creation of a hinged lamellar corneal flap which diameter is 9.5mm with a microkeratome,then excimer laser is used to make a refractive cut on the underlying stromal bed and flap is repositioned.We have discovered some complications during and after surgery along with doing more and more basic and clinic research on LASIK.For example forming a thin flap , a free and/or incomplete flap etc during LASIK.There are other complications such as keratectasia,kertoconus and refractive regression etc after LASIK.Commonly believed there is a direct relation between corneal flap thickness and flap complications.In order to reduce these complications and to elevate the effect of operation,it is important to study the factors that affect the flap thickness in LASIK.During the flap cuting,the distance between the fixed microkeatomeplate and the edge of the metal blade determines the thickness of the flap,and it is known to vary within a certain range for any given microkeratome because of the effect of several factors such as corneal thickness and curvature,suction pressure,intraocular pressure , turbine and translational velocities of the microkeratome,the degree of wetness in the operation room etc.This experiment is to study the effect of suction duration on corneal flap thickness in LASIK,so to reduce corneal flap complications.Materials and methodsl.Materials:45 porcine eyes were kept at 4c in moist chambers and were used for experiments within 4 hours of enucleation.The status of epithelium in each eye was inspected by slit lamp before experiment,and eyes with epithelial defect were excluded to avoid any bias in corneal thickness, Moria M2 microkeratome, Non-contact ophthalmotonomete, Automatic keratometer.Automatic ultrasonic pachymeter.Slit lamp.Stop watch.slide gaud.etc2.Methods:The intraocular pressure (IOP) of each porcine eye was controlled by the injection of normal saline through the optic never and maintained from 20 to 25 mmHg.They were measured corneal thickness and curvature and were assigned to three groups, 10 seconds group(n=15eyes ),20 seconds group(n=15 eyes ),and 30 seconds group(n=15 eyes ).Then simulated LASIK surgery of the right eye,Corneal flap were made by using an suction ring which diameter is 9.5mm and suction time was 10 sec,20 sec and 30 sec respectively.The remaining corneal stromal thickness was measured centrally.The difference in corneal thickness and the remaining stromal thickness was defined as the flap thickness.The diameter of corneal flap is measured by using slide gaud.3.Statistical analysisrStatistical analysis was performed with t tests by SPSS 10.0 software.ResultsMean corneal flap thickness in group 1(10 sec ),group 2 (20 sec ) and group 3 (30 sec ) was 147.2 15.96um,157.33 24.85um and 167.6 22.37um respectively.There was a statistically significant difference between group 1 (10 sec ) and group 3 (30 sec ) (P=0.008).The mean corneal flap diameter in groups 1,2 and 3 was 8.668 0.1601mm,8.8627 0.2534mm and 9.06 0.2238mm,respectively.A statistically significant difference was found amomg groups.DiscussionThere are many factors that can affact corneal flap thickness duringLASlK,and there are some reports on this subject,but few are concerned about the effect of suction duration on corneal flap thickness.I think because the eyeball is relatively malleable,continuous suction delievered by a suction ring can change the shape of the cornea and eyeball,causing oculi axes to stretch and cornea to bulge above the cutting plane,resulting in the changes of flap thickness and diameter.Corneal flap thickness can be controlled by suction duration is useful in several clinical aspects. One can minimize the risk of cutting an overly thick flap by decreasing suction duration,which helps to maintain a residual stromal bed thicker than 250um,which reduces更多还原