Corneal Ectasia detection by epithelium pattern standard deviation from optical coherence tomography.

Abstract

To test the ability of the corneal epithelial pattern standard deviation to distinguish between normal and cases with corneal ectatic condition. Instituto de Olhos Renato Ambrósio, Rio de janeiro, Brazil. Cross-sectional retrospective study. Patients were stratified into four groups based on clinical data and. (Groups 1 and 2 comprised one eye randomly selected from 105 patients with normal corneas (N) and 86 patients with bilateral keratoconus (KC). Groups 3 and 4, respectively comprised 11 ectatic eyes with no surgical treatment for keratoconus (VAE-E) from patients whose fellow eyes (61) presented with normal topographic patterns (VAE-NT). Corneas were scanned using an OCT system (RT Vue) and Scheimpflug corneal tomography (Pentacam), and also had biomechanical assessment through the Corvis ST. Corneal epithelial thickness maps were analyzed and the pattern standard deviation (PSD) value was calculated. The area under the ROC curve analysis was used to evaluate the diagnostic accuracy of the indices. Epithelial PSD was significantly different across the four groups (p<0.0001). The pairwise comparison revealed that the normal group presented significantly lower values than both ectasia groups (KC and VAE-E, p<0.0001) and the VAE-NT group (p=0.0008). There was no significant difference between KC and VAE-E (p=0.4284), while they were significantly higher than the VAE-NT group (p<0.0001 and p=0.0004). Epithelial PSD can be used to detect abnormal epithelial thickness patterns. Corneal epithelial thickness changes could be detected accurately in keratoconus patients, even in the form fruste of the disease.