Purpose: To determine whether pancorneal rigid gas-permeable toric edge contact lenses (pancorneal RGP-CL) fitting could be improved by using non-central corneal shape predictors, and to compare these parameters with respect to age and gender in patients with keratoconus. Methods: The current study was a retrospective study including patients with clinically evident keratoconus (on videokeratography) from three medical centres located in the Netherlands. Medical history, visual acuity, refraction, and contact lens characteristics were documented. All participants underwent ophthalmic examination including measurement of K-values (steepest, flattest, mean, as a non-central parameter the minimum radius [. K-minimum], and all combined) using corneal topography. Fitting of contact lenses was based on the fluorescence pattern as seen during slitlamp examination. Results: A total of 378 eyes of 218 patients with keratoconus were included. Of these, 257 (68%) were fitted with a pancorneal RGP-CL. The central K-values, K-steep and K-flat, performed well in predicting the base curve radius, though, for pancorneal RGP-CL the non-central K-minimum added most (35.5%) to the total explained variance in base curve radius. Regarding age and gender, women tended to have larger K-values than men. No differences in K-values were found with respect to age. Discussion: We found that including the K-minimum as a non-central parameter may improve prediction of the best base curve radius for pancorneal RGP-CL and may reduce the number of trial contact lenses. In line with other studies, suggestive evidence was found for a difference in pattern of progression of keratoconus with gender, but not with age.

Base curve radius, K-values, Keratoconus, Keratometry, Pancorneal toric edge rigid gas-permeable contact lenses
dx.doi.org/10.1016/j.clae.2013.07.005, hdl.handle.net/1765/63422
Contact Lens and Anterior Eye
Department of Ophthalmology

Ramdas, W.D, Vervaet, G, & Bleyen, I. (2014). Corneal topography for pancorneal toric edge rigid gas-permeable contact lens fitting in patients with keratoconus, and differences in age and gender. Contact Lens and Anterior Eye, 37(1), 20–25. doi:10.1016/j.clae.2013.07.005