A bitoric gas permeable hard contact lens with spherical power effect.

A 36 lens fitting set of gas permeable hard (Polycon II) bitoric contact lenses with spherical power effect in vivo was used to fit 50 patients. Thirty six patients (66 eyes) were correctly fitted with spherical power effect (SPE) lenses while 14 patients (27 eyes) required cylinder power effect (CPE) lenses. The mean flat base curve was 0.45 D.K. flatter than the mean flat corneal K reading, and the mean base curve toricity was 0.50 D.K. less than mean corneal toricity. Overall patient response was good to excellent for 82% of the patient sample.