圆锥角膜的光密度分析

目的 使用Pentacam对圆锥角膜和健康角膜的光密度进行测量,比较健康角膜与不同等级圆锥角膜的透明度.方法 使用Pentacam眼前节分析系统测量对照组(30例30眼正常角膜)以及圆锥角膜组(36例36眼圆锥角膜)的光密度,以角膜顶点为中心,分别测量0～2 mm、2～6 mm、6～ 10 mm、10 ～ 12 mm直径范围的前层(120μm)、后层(60 μm)以及中间层的角膜光密度.使用Amsler-Krumeich分级方法对圆锥角膜进行分级,对比不同等级光密度差异.分析圆锥角膜光密度与厚度、陡峭K值的相关性.结果 总直径的全层角膜光密度圆锥角膜组(17.96±3.23)和对照组(17.39±1.95)之间差异无统计学意义(P =0.124);但是在0～2 mm直径范围内的前层、中层、全层,2～6mm直径范围内的前层以及总直径的前层中,圆锥角膜组的光密度均显著高于对照组(均为P＜0.05).按照圆锥角膜等级分组,对照组角膜光密度与轻度圆锥角膜组各层比较,差异均无统计学意义(均为P＞0.05),但对照组角膜光密度与中度圆锥角膜组0～2mm直径范围内的前层比较差异有统计学意义(P＜0.05).重度圆锥角膜在0～2 mm直径范围内各层光密度较对照组、轻度圆锥角膜组、中度圆锥角膜组均显著增高(均为P＜0.05),在2～6 mim直径范围和总直径的前层、中层和全层与其余三组相比均显著增加(均为P＜0.05).圆锥角膜组的陡峭K值与0～2 mm直径范围的总角膜光密度显著相关(P＜0.05).圆锥角膜组的角膜顶点以及角膜最薄点的厚度与光密度也存在明显的相关性(均为P＜0.05).结论 相比正常角膜,轻度圆锥角膜光密度不发生改变,中度圆锥角膜光密度增高主要发生于角膜前层0～2 mm直径范围内,重度圆锥角膜光密度增高主要发生于角膜前层0～6 mm直径范围内和角膜中层2 mm直径范围内,而且圆锥角膜光密度随疾病发展而增高.角膜光密度是圆锥角膜的一个重要参考指标,可以用来检测圆锥角膜发病进程以及治疗效果.

Analysis of densitometry of keratoconus

Objeetive To compare corneal densitometry measured by Pentacam in normal and keratoconic eyes,and assess the differences in densitometry values among the stages of keratoconus.Methods Densitometry values for 66 eyes (36 eyes from keratoconus group,30 eyes from control group) were obtained for the 0-2 mm,2-6 mm,and 6-10 mm zones of the anterior (up to 120 mm),posterior (posterior 60 mm),and central (between the anterior and posterior) cornea.The differences in densitometry values among the stages of keratoconus were compared.Pearson correlation analysis was used to access the relationship among Keratoconus optical density,cornea thickness and flat K values.1~l~ In total diameter,the corneal densitometry between keratoconus group (17.96 ± 3.23) and control group (17.39 ± 1.95) was not significant different(P =0.124),but there were significant differences between the groups for densitometry measurements in central 2.0 mm zones(anterior,central and total layers),annulus 2-6 mm(anterior layers) and anterior layers in total diameter (all P ＜0.05).Divided by different stage of keratoconus,the anterior layer in mild Keratoconus had no difference with control group(P ＞0.05),but therewere significant differences in moderate keratoconus group(all P ＜ 0.05).In severe Keratoconus group,a statistically significant difference was present at the 2 central annuli in total thickness and annulus 2-6 mm (anterior,central and total layers) with control group (P ＜ 0.05).The correlation between corneal densitometry and the other parameters,including cornea thickness and flat K values were significant (all P ＜ 0.05).Conelusion Compared with normal cornea,there is no change in mild keratoconus.The increase of corneal densitometry in moderate keratoconus group happens in the anterior layers of 0-2 mum zones.The anterior layers of 0-6 mm zones and central layers in 0-2 mm zones in severe keratoconus group are higher than those of control group.More advanced cases present a higher corneal densitometry.Corneal densitometry is an important characteristic of keratoconus,it can be used to detect the process and therapeutic effect of keratoconus.