圆锥角膜的光密度分析及其与角膜形态学的相关性研究

Corneal densitometry analysis and its correlation with corneal topography in keratoconus

目的对比正常角膜与圆锥角膜(KC)的角膜光密度(CD),并分析CD与角膜形态学参数之间的相关性。设计横断面研究。研究对象2017-2019年北京同仁医院KC患者162例(162眼)(KC组)和健康志愿者41例(41眼)(NL组)。方法用Pentacam三维眼前节分析系统测量CD,以角膜顶点为中心,分别测量0~2 mm、2~6 mm、6~10 mm、10~12 mm和0~12 mm直径范围的前层(120μm)、中间层、后层(60μm)以及全层的CD。基于Pentacam的TKC分级法将KC按照严重程度分为轻度KC(TKC=1)、中度KC(TKC=1~2,2)和重度KC(TKC=3,3~4,4)。Bonferroni矫正检验或Kruskal-Wallis检验比较组间CD差异。Pearson相关分析或Spearman相关分析评估CD与角膜形态学参数之间的相关性。主要指标不同直径范围和深度层面的CD、角膜曲率最大值(Kmax)、中央角膜厚度(CCT)、角膜最薄点厚度(TCT)。结果NL组,总KC组,轻度、中度及重度KC组在0~2 mm前层的CD分别为21.67±1.60,21.90(18.70~98.70),21.6(18.70~24.80),21.60(19.30~29.10)及22.80(20.00~98.70)。对于0~2 mm前层的CD,总KC组较NL组显著增高(P=0.043),轻度、中度KC组与NL组之间无显著差异(P均>0.05),而重度KC组较轻度、中度KC组和NL组均显著增高(P均<0.05)。其他区域CD组间均无统计学差异(P均>0.05)。KC组0~2 mm前层的CD与Kmax显著正相关(R=0.181,P=0.03),与CCT和TCT显著负相关(R=-0.172,P=0.03;R=-0.171,P=0.04)。结论KC前层角膜中央区的CD较正常人高,且KC越严重CD越高。KC前层角膜中央区的CD与Kmax、CCT和TCT显著相关。CD或许可作为评估KC进展程度的指标之一。

Objective To compare corneal densitometry(CD)between keratoconus(KC)and normal cornea,and to investigate the correlation between CD and topographic parameters.Design Cross-sectional study.Participants A total of 162 keratoconic patients(162 eyes)(KC group)and 41 normal subjects(41 eyes)(NL group)were included from Beijing Tongren Hospital from 2017 to 2019.Methods CD values were obtained for the 0~2 mm,2~6 mm,6~10 mm,10~12 mm and 0~12 mm zones of the anterior(up to 120μm),posterior(posterior 60μm),central(between the anterior and posterior)and total cornea by Pentacam HR.The Pentacam provides a topographic keratoconus classification for staging the disease in grades 1 to 4.Cases were divided into mild,grade 1;moderate,from grades 1 to 2 and grade 2;and severe,grade 3,from grades 3 to 4 and grade 4.Bonferroni multiple comparisons test or Kruskal-Wallis test was used to compare CD between different groups.Pearson’s correlation test or Spearman’s correlation test was used to determine the correlations between CD and topographic parameters.Main Outcome Measures CD values over different corneal annular concentric zones and depths,maximum keratometry(Kmax),corneal central thickness(CCT)and thinnest corneal thickness(TCT).Results The CD values of the anterior 0 to 2 mm layer for the NL group,KC group,KC mild,KC moderate and KC severe were 21.67±1.60,21.90(18.70~98.70),21.6(18.70~24.80),21.60(19.30~29.10)and 22.80(20.00~98.70),respectively.There were significant differences between KC group and NL group for the CD of the anterior 0 to 2 mm layer(P=0.043).There were no significant differences between KC mild,KC moderate and NL group for the CD of the anterior 0 to 2 mm layer(all P>0.05).There were significant differences between KC severe and the other groups for the CD of the anterior 0 to 2 mm layer(all P<0.05).There were no significant differences between groups for the CD of the remaining corneal annuluses and layers(all P>0.05).The CD values of the anterior 0 to 2 mm layer significantly and positively correlated with the Kmax values(R=0.181,P=0.03),and significantly and negatively correlated with CCT and TCT values(R=-0.172,P=0.03 and R=-0.171,P=0.04,respectively).Conclusion The CD values of the anterior 0 to 2 mm layer are higher for the keratoconic cornea than in the normal cornea.The CD level is higher in more advanced stages.There are significant correlations between the CD values of the anterior 0 to 2 mm layer of the keratoconic cornea and the Kmax,CCT and TCT values.CD may be a useful index of KC progression.