Correlation of corneal endothelial changes with different stages of keratoconus

The aim was to study the corneal endothelial count and morphology in patients with keratoconus by specular microscopy and to correlate them to the stage of keratoconus.

Forty eyes of 29 patients with keratoconus were enrolled in this cross-sectional cohort study. Corneal endothelium was evaluated using specular microscopy, and corneal topography and thickness data were obtained from Scheimpflug-based corneal tomography. Eyes were classified into stages 1 through 4 of keratoconus according to Amsler classification, using keratometry and pachymetry readings obtained from corneal tomography.

Eleven eyes (27.5%) had stage 1, 17 eyes (42.5%) had stage 2, and 12 eyes (30%) had stage 3. Specular microscopy was not possible in stage 4. There was no statistically significant correlation between the stage of keratoconus and the endothelial cell density (ECD) (r = 0.018, P = 0.91), coefficient of variation (CV) (r = -0.011, P = 0.94), or percentage of hexagonality (6A) (r = -0.112, P = 0.51). When mild-to-moderate keratoconus (stages 1 and 2) was compared with severe keratoconus (stage 3), the difference was not significant regarding ECD (P = 0.1), CV (P = 0.3), or 6A (P = 0.4). However, there was a trend toward lower ECD and percentage of hexagonality, and a higher CV with advancing disease.

Up to stage 3, keratoconus does not significantly affect the corneal endothelium, as measured by specular microscopy. Eyes with stage 4 could not be studied by specular microscopy and may require other imaging methods such as confocal microscopy.