Endothelial alterations in 712 keratoconus patients.

PURPOSE: To investigate the effect of the severity of keratoconus on the corneal endothelium using specular microscopy.

METHODS: Seven hundred and twelve eyes from the Homburg Keratoconus Center (HKC) database were included in this retrospective study. Corneal endothelium was evaluated using the Tomey EM-3000 specular microscope. Keratoconus-related topographic and tomographic data were obtained from Scheimpflug-based tomography (Oculus Pentacam® HR). Eyes were classified into stages 0 (healthy) to 4 (severe keratoconus) according to the Topographic Keratoconus Classification (TKC). Subgroups were analysed based on contact lens (CL) type (none/rigid/soft).

RESULTS: The frequencies of keratoconus stages 0/1/2/3/4 according to TKC were 169/94/206/166/77. The endothelial cell density (ECD) for the endothelial cell area for TKC 0/1/2/3/4 was 2611/2624/2557/2487/2401 cells per mm² and the coefficient of variation (CV) was 40.9/40.0/41.6/46.2/49.0%, respectively. The more severe the keratoconus stage, the lower the endothelial cell count (p < 0.001) and the higher the CV (p < 0.001). No contact lens wearing was noted in 207 eyes (NoCL), rigid CL in 200 (RCL) and soft CL in 54 (SCL). CD for NoCL/RCL/SCL was 2523/2533/2644 per mm² and CV was 41.8/54.1/43.1%, respectively. A significant difference in CV was found between NoCL and RCL (p = 0.02), and no significant difference in CV was found between NoCL and SCL (p = 0.07). Endothelial cell density (ECD) did not differ significantly between NoCL and RCL or SCL.

CONCLUSION: Endothelial cell density (ECD) decreases and CV increases significantly with increasing tomographic severity of keratoconus. In patients with RCL compared to eyes without CL wear, we found a statistically significantly higher CV in the endothelial cell size.