Rigid contact lens fitting based on keratometry readings in keratoconus patients: predicting formula.

Aim: To find a simple mathematical correlation between the lens base curve (BC) and keratometry findings (krf).

Methods: This retrospective study included 400 keratoconic eyes (350 patients) previously fit with rigid contact lenses at an academic eye center over a five year period. The patients were classified into five groups based on the keratometry findings (krf<7, krf:7-8, krf>8, krf-krs (difference between two keratometry; flat and steep)= 0.