The Effect of Topical Cyclopentolate on Anterior Segment Parameters in Patients with Keratoconus

To investigate the effect of cycloplegia on anterior segment structures in keratoconus and forme fruste keratoconus patients using corneal topography.

In this study, 40 patients with keratoconus (group 1), 40 patients with forme fruste keratoconus (group 2), and 40 healthy subjects (group 3) were evaluated prospectively. Flat keratometry (K) value (K1), steep K value (K2), mean K value (Kmean), maximum K value (Kmax), corneal astigmatism value, anterior chamber depth (ACD), symmetry index front, symmetry index back, thinnest corneal thickness, central corneal thickness and corneal volume were measured using Sirius topography before and after cycloplegia. Results were compared with one way ANOVA test.

The mean age of the participants was 24.4±6.2 years for group 1, 26.3±4.3 years for group 2 and 26.5±6.1 years for group 3. There was no difference between the groups with respect to mean age and gender (p>0.05). Mean K1 value was 45.54±2.43 diopters (D) before cycloplegia and 45.46±2.48 D after cycloplegia for group 1 (p=0.044). K1 value didn’t change significantly after cycloplegia for group 2 and 3 (p=0.275, p=0.371). There was no significant difference in K2 and Kmean values after cycloplegia for all groups (p>0.05). Kmax value decreased significantly after cycloplegia in group 1 (p=0.001), but the difference was not significant for group 2 and 3 (p=0.087, p=0.241). ACD increased significantly after cycloplegia in all groups (p=0.001).

Cycloplegia causes corneal flattening only in manifest keratoconus patients, leading to an increase in ACD in all groups.