Differences in anterior chamber depth in keratoconus patients with binocular very asymmetry ectasia

Background To evaluate the difference in anterior chamber depth (ACD) between two eyes among keratoconus patients with binocular very asymmetric ectasia (VAE) and to explore the influencing factors. Methods The corneal curvature and ACD in both eyes of patients with VAE were measured by Sirius (version 3.2, CSO, Italy) at the following points: corneal vertex, maximum curvature (apex), and the 1.5 mm, 2.5 mm, and 3.5 mm superior-, inferior-, nasal-, temporal-paracentral from center. The mean pupil power (MPP) and corneal morphology parameters were also measured. Correlations between ACD and curvature and morphology parameters were analyzed by linear regression. Results 172 eyes of 86 patients (9 to 45 years) were classified into the VAE-N ( n = 86) group and the VAE-E group ( n = 86) based on the corneal morphology. The central (3.32 ± 0.27 mm versus 3.43 ± 0.29 mm, P < 0.001) and paracentral ACDs increased significantly in the VAE-E group, and the corneal morphology parameters were also significantly higher. The central ACD was significantly correlated with the MPP ( r = 0.465), KVf/b (Keratoconus Vertex front/back) ( r = 0.306, r = 0.327), and BCVf/b (Baiocchi Calossi Versaci front/back) ( r = 0.356, r = 0.416). Linear regression showed good relationships between △ACD and △MPP (R 2 = 0.429) and △KVf/b (R 2 = 0.504, R 2 = 0.536). Conclusions The ACD was larger in the VAE-E group. The difference in ACD between the VAE-E and VAE-N groups was significantly correlated with corneal curvature and the extent of corneal elevation, indicating the influences of both the corneal magnification effect and corneal ectasia on ACD.