Instituto Oftalmológico de Alicante, Vissum Corporation, Alicante, Spain.
Graefes Arch Clin Exp Ophthalmol. 2013 Jun;251(6):1547-55. doi: 10.1007/s00417-013-2261-3. Epub 2013 Jan 20.
To analyze and compare the relationship between anterior and posterior corneal shape evaluated by a tomographic system combining the Scheimpflug photography and Placido-disc in keratoconus and normal healthy eyes, as well as to evaluate its potential diagnostic value.
Comparative case series including a sample of 161 eyes of 161 subjects with ages ranging from 7 to 66 years and divided into two groups: normal group including 100 healthy eyes of 100 subjects, and keratoconus group including 61 keratoconus eyes of 61 patients. All eyes received a comprehensive ophthalmologic examination including an anterior segment analysis with the Sirius system (CSO). Antero-posterior ratios for corneal curvature (k ratio) and shape factor (p ratio) were calculated. Logistic regression analysis was used to evaluate if some antero-posterior ratios combined with other clinical parameters were predictors of the presence of keratoconus.
No statistically significant differences between groups were found in the antero-posterior k ratios for 3-, 5- and 7-mm diameter corneal areas (p ≥ 0.09). The antero-posterior p ratio for 4.5- and 8-mm diameter corneal areas was significantly higher in the normal group than in the keratoconus group (p<0.01). The k ratio for 3, 5, and 7 mm was significantly higher in the keratoconus grade IV subgroup than in the normal group (p<0.01). Furthermore, significant differences were found in the p ratio between the normal group and the keratoconus grade II subgroup (p ≤ 0.01). Finally, the logistic regression analysis identified as significant independent predictors of the presence of keratoconus (p<0.01) the 8-mm anterior shape factor, the anterior chamber depth, and the minimal corneal thickness.
The antero-posterior k and p ratios are parameters with poor prediction ability for keratoconus, in spite of the trend to the presence of more prolate posterior corneal surfaces compared to the anterior in keratoconus eyes.
分析并比较角膜地形图系统（结合 Scheimpflug 摄影术和 Placido 盘）评估的圆锥角膜和正常健康眼的前后角膜形态的关系，并评估其潜在的诊断价值。
本研究为病例对照研究，纳入了 161 例（161 只眼）年龄 7-66 岁的受试者，分为正常组（100 例 100 只眼）和圆锥角膜组（61 例 61 只眼）。所有患者均接受了全面的眼科检查，包括 Sirius 系统（CSO）眼前节分析。计算角膜曲率前后比（k 比）和形状因子（p 比）。采用逻辑回归分析评估一些前后比与其他临床参数的组合是否为圆锥角膜存在的预测因子。
三组角膜直径（3、5、7mm）的前后 k 比在两组间无统计学差异（p≥0.09）。4.5mm 和 8mm 角膜直径的前后 p 比在正常组中显著高于圆锥角膜组（p<0.01）。4 级圆锥角膜亚组的 3、5、7mm k 比显著高于正常组（p<0.01）。此外，正常组与 2 级圆锥角膜亚组的 p 比之间存在显著差异（p≤0.01）。最后，逻辑回归分析确定 8mm 前表面形状因子、前房深度和最小角膜厚度是圆锥角膜存在的显著独立预测因子（p<0.01）。
尽管圆锥角膜眼的后表面更趋于扁平，但前后 k 和 p 比是圆锥角膜预测能力较差的参数。
