Corneal differences between healthy and subclinical patients assessed using two diferente corneal tomographers

ABSTRACT Purpose: To analyze subclinical keratoconus topography indexes using Pentacam and Orbscan-II measurements to identify evidences for seeking sensitive indexes to screen and diagnose subclinical keratoconus. Methods: Fifty healthy participants (50 eyes) and 40 patients with subclinical keratoconus (40 eyes) were included. Seven common parameters including corneal thickness at the thinnest point; minimum curvature of the front surface (minimum simulated keratometry value, SimK’s Min); maximum curvature of the front surface (maximum simulated keratometry value, SimK’s Max); the frontal corneal surface best-fit spherical radius of the curvature; the back corneal surface best-fit spherical radius of curvature; the anterior corneal surface height (anterior Diff value); and the posterior corneal surface height (posterior Diff value) measured by Pentacam and Orbscan-II between normal and subclinical keratoconus eyes were compared. Results: Statistical differences between the healthy and subclinical keratoconus groups (p<0.01) were found in all corneal parameters measured using both devices. Differences in the minimum curvature of the front surface (SimK’s Min), thinnest point, anterior Diff value, and posterior Diff value were significant between Pentacam and Orbscan-II in the subclinical keratoconus group (p<0.05). Conclusion: The findings of this study identify the differences between normal and subclinical keratoconus eyes at the minimum curvature of the front surface, maximum curvature of the front surface, frontal corneal surface best-fit spherical radius of curvature, back corneal surface best-fit spherical radius of curvature, Anterior Diff value, and Posterior Diff value measures using Orbscan II and Pentacam that can help eye care practitioners clinically diagnose subclinical keratoconus.

摘要：
**目的**：利用Pentacam眼前节分析仪（Pentacam）与Orbscan-II眼前节分析仪（Orbscan-II）的测量数据，分析亚临床圆锥角膜（subclinical keratoconus）的角膜地形图指标，以期筛选出用于筛查及诊断亚临床圆锥角膜的敏感指标。
**方法**：本研究纳入50名健康受试者（共50只眼）及40名亚临床圆锥角膜患者（共40只眼），比较正常眼与亚临床圆锥角膜眼两组经两种仪器测量得到的7项常用角膜参数，包括：角膜最薄点厚度、角膜前表面最小曲率（模拟角膜曲率最小值，SimK’s Min）、角膜前表面最大曲率（模拟角膜曲率最大值，SimK’s Max）、角膜前表面最佳拟合球面曲率半径、角膜后表面最佳拟合球面曲率半径、角膜前表面高度（前表面Diff值）及角膜后表面高度（后表面Diff值）。
**结果**：两种仪器测量的所有角膜参数在健康组与亚临床圆锥角膜组间均存在统计学差异（p<0.01）；在亚临床圆锥角膜组中，Pentacam与Orbscan-II在角膜前表面最小曲率（SimK’s Min）、角膜最薄点、前表面Diff值及后表面Diff值这四项指标上存在显著差异（p<0.05）。
**结论**：本研究结果显示，经Orbscan-II与Pentacam测量得到的角膜前表面最小曲率、前表面最大曲率、角膜前表面最佳拟合球面曲率半径、角膜后表面最佳拟合球面曲率半径、前表面Diff值及后表面Diff值这六项指标，在正常眼与亚临床圆锥角膜眼间存在显著差异，可为眼科临床医师临床诊断亚临床圆锥角膜提供可靠参考依据。