Rigid contact lens fitting relationships in keratoconus

Purpose. Although the influence of flat-fitting contact lenses on corneal s carring in keratoconus is frequently debated, the current standard of care with regard to the apical fitting relationship in keratoconus remains undoc umented. Methods. Patients were examined at baseline in the Collaborative L ongitudinal Evaluation of Keratoconus (CLEK) Study (N = 1209). Patients wea ring a rigid contact lens in one or both eyes (N = 808) had their habitual rigid contact tenses analyzed, and the fluorescein patterns and base curves were compared to the first definite apical clearance lens (FDACL). The FDA CL is the flattest lens in the CLEK Study trial lens set that exhibits an a pical clearance fluorescein pattern. For patients wearing a rigid contact l ens in both eyes, one eye was selected randomly for analysis. Results, Twel ve percent of the rigid contact lens-wearing eyes were wearing tenses fitte d with apical clearance based upon the clinician's fluorescein pattern inte rpretation. The remainder (88%) was wearing lenses fitted with apical touch . For mild (steep keratometric reading <45 D) keratoconus corneas, the mean estimate of the base curve to cornea-fitting relationship was 1.18 D flat (SD +/- 1.84 D); moderate (steep keratometric reading: 45 to 52 D) corneas were fitted on average 2.38 D fiat (SD +/- 2.56 D); and severe (steep kerat ometric reading >52 D) corneas were fitted an average of 4.01 D flat (SD +/ - 4.11 D), Conclusions. Despite the potential risk for corneal scarring imp osed by flat-fitting rigid contact lenses, most CLEK Study patients wear fi at-fitting lenses. Overall, rigid lenses were fitted an average of 2.86 D ( SD +/- 3.31 D) flatter than the FDACL.