Initial Power of Rigid Gas Permeable Contact Lenses in Patients with Keratoconus

PURPOSE: To simplify the fitting process, this study was designed to predict the initial power of contact lenses using the regression model based on manual Javal keratometry data and refractive errors. METHODS: In this retrospective study, 121 eyes of 69 patients with keratoconus (KCN) were fitted with a specific trial set of rigid gas permeable contact lenses based on the standard criterion of “three-point touch” over a 7-year period. Power of the cornea was measured using Javal keratometer. Refractive errors and over refraction of patients were diagnosed using Topcon autorefractometer (RM-A2000) and confirmed by Heine beta 2000 retinoscope. RESULTS: The results of multiple linear regression showed the following equation: power of contact lens = −14.368 (constant of the final multiple regression model), +0.475 (spherical refraction), and +0.275 (flatter corneal power). CONCLUSIONS: The results of this study revealed that lens power has a significant relationship with the power of the flat corneal meridian and spherical refractive error in KCN patients. The obtained regression model can be used to shorten patients’ chair time and optometric examination for predicting the power of contact lens.