摘要 目的 探讨角膜切削术深度与准分子激光治疗近视疗效的关系。方法 Tomey SP-2000微型超声测厚仪检测79例(151眼)Haze ＜0.5级的PRK术前及术后0.5a角膜中央厚度，用术前等值球镜屈光度分别与理论角膜中央切削深度(X1)、角膜中央实际减少厚度(X2)和X1-X2之绝对值作直线回归分析，并用直线回归分析术后裸眼视力与X1-X2之绝对值的相互关系。结果 等值球镜屈光度与角膜中央理论切削深度的相关系数r=0.44,P＜0.01，与角膜中央理论切削深度和角膜中央实际减少厚度变异值r=0.40,P＜0.01。术后裸眼视力与角膜中央理论切削深度和角膜中央实际减少厚度变异值r=-0.51,P＜0.01。结论 PRK角膜中央切削深度越深，治疗屈光度越高；角膜中央厚度的实际减少值越接近理论切削深度，疗效越好；近视度数越高，角膜中央厚度减少值与理论切削深度值间变异越大。
Correlation of corneal ablation depth and results of PRK for myopia
SHEN Zheng-Wei,MA Qun,YIN He,HUANG Zhen-Xi,LI Li,ZHOU Xiong,WU Jin-Tao
Abstract Objective To study the correlation between the corneal ablation depth and the results of photorefractive keratectomy(PRK) for myopia.Methods The central coreal thickness of all patients(79 cases,151 eyes)with "Haze" less than 0.5 scale were examined before and after operation with Tomey SP-2000 pachymeter.Spherical equivalent refraction before operation was regressively compared with corneal ablation depth in laser(X1)、actual central corneal thickness decreasion (X2) and differences of X1 and X2 individually.Linear regressive analysis was used to compare the best corrective visual acuities after operation and the difference of X1 and X2.Results Correlation coefficient of spherical equivalent with corneal ablation depth in laser(X1) was 0.86,and that with actual central corneal thickness decreasion(X2) was 0.44,and that with difference of X1 and X2 was 0.44.Correlation coefficient of best corrective visual acuity after operation with the difference of X1 and X2 was -0.41.Conclusion The more central corneal ablation is after PRK,the higher the treatment refraction will be;The patients of little difference of r had good result;The higher the myopia is the more change the actual central corneal thickness decreasion with ablation depth in laser will happen.
Key words laser;photorefractive keratectomy;cornea;myopia;ablation depth;visual acuity
［Rec Adv Ophthalmol 1999;19(3)∶182-183］
准分子激光角膜切削术(photorefractive keratectomy,PRK)治疗低中度近视的疗效已得到肯定，并在世界范围内广泛应用［1，2］。PRK治疗近视的原理是在角膜前表面切削成一凹面，其疗效理论上应与角膜切削深度的稳定性有关。本文前瞻性用SP-2000微型超声测厚仪对PRK术前、后角膜厚度进行检测，探讨角膜切削深度与PRK疗效的关系。
1 材料与方法
1.1 对象 79例(151)眼均为1995年11月～1996年4月我院准分子激光中心治疗随访0.5a以上，资料完整的近视眼病人，男39例75眼，女40例76眼；年龄19～50a，近视球镜屈光度-1.25～-17.25D，平均-7.38±3.88D，近视散光度-0.50～-4.50D，平均等值球镜屈光度为-8.25±4.04D。
1.2 方法 术前常规检影、眼前节及眼底、角膜地形图检查；用Tomey SP-2000微型超声测厚仪检测取角膜中央厚度，测厚仪频率为20Hz，精度为5μm。取角膜中央3次平均值；美国Chiron Vision公司生产的Keracor 116型准分子激光机，Ⅰ～Ⅴ光区切削治疗近视眼。
术前记录等值球镜屈光度，角膜中央厚度，Keracor 116型准分子激光机治疗软件的理论角膜切削深度。术后0.5a复查时角膜Haze＜0.5级者记录角膜中央厚度平均值和裸眼视力。预矫正等值球镜屈光度绝对值Y1，分别与理论角膜切削深度X1，角膜中央实际减少厚度(术前角膜中央厚度减术后0.5a角膜中央厚度)X1和X1与X2差值的绝对值分别作直线回归分析；设术后视力为Y2，与X1、X2差值的绝对值作直线回归分析。统计学处理用t检验。
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