Pentacam三维眼前节分析系统对各期圆锥角膜后表面形态的研究

Research on posterior surface topography of keratoconus with Pentacam

目的分析各期圆锥角膜后表面的形态特点,为完善圆锥角膜形态特点的描述提供参考。方法选取各期圆锥角膜患者(符合Rabinowitz诊断标准)248例(248眼)及正常对照(正视或低度近视患者)143例(143眼)。使用Pentacam三维眼前节分析系统检测角膜,统计分析后表面屈光度、后表面高度、角膜厚度及各指标间的相关性,计算各指标的ROC曲线下面积。结果临床组、亚临床组、可疑圆锥角膜组和正常组的平均后表面最大屈光度分别为-8.5D,Q=4;-6.2D,Q=0.5;-5.6D,Q=0.3;-5.5D,Q=0.3。平均后表面最大高度分别为55μm,Q=36;23μm,Q=14;11μm,Q=8.5;7μm,Q=6。平均角膜最薄厚度分别为437μm,Q=94;502μm,Q=60;502.5μm,Q=35.5;540μm,Q=49。后表面最大屈光度和后表面最大高度在各组之间差异均有统计学意义(P=0.0001)。各组屈光度最大点、最高点、角膜最薄点主要分布在中央3mm区域的下方。后表面屈光度最大值、后表面高度最大值的ROC曲线下面积最大。结论角膜后表面屈光度、后表面高度的变化是早期圆锥角膜形态改变的重要特点。

Objective Many researches on keratoconus focus on the features of the anterior surface of cornea.Our present study was to investigate the corneal posterior surface topography in different clinical stages of keratoconus.Methods248 eyes from 248 subjects with keratoconus at subclinical stage,clinical stage,suspectival patients （Rabinowitz diagnosis standards） and 143 normal eyes from 143 subjects with emmetropia or low myopia were enrolled in this research.The ocular anterior segment was examined with Pentacam Measurement and Evaluation System,and the posterior surface refractive power,posterior surface elevation and the corneal thickness was recorded.The correlation among several indexs,the area under the ROC curve were statistically analyzed.ResultsThe maximum refractive power of corneal posterior surface in four groups was -8.5D,Q=4;-6.2D,Q=0.5;-5.6D,Q=0.3;-5.5D,Q=0.3,respectively.The maximum elevation of corneal posterior surface was 55μm,Q=36;23μm,Q=14;11μm,Q=8.5;7μm,Q=6,respectively.The thickness of corneal thinnest point was 437μm,Q=94;502μm,Q=60;502.5μm,Q=35.5;540μm,Q=49,respectively.There was a statistically significant difference in maximum refractive power and elevation among four groups （P=0.000）.The corneal thinnest point,maximum refractive power point and elevation point were mainly located at the inferior 3mm zone to cornea.The largest ones of the area under ROC were at the highest refractive power point and highest elevation point.ConclusionThe changes of posterior surface refractive power and posterior surface elevation are the important features of keratoconus in early stage.