Performance and predictability of a new large diameter contact lens design in keratoconic corneae

Objectives: To evaluate the clinical performance and predictability using corneal topography in the fitting of a new large-diameter rigid gas permeable (RGP) contact lens design in eyes with keratoconus (KCN). Methods: This study presents a review of eyes fitted with Alexa ES lenses for nonsurgical optimisation of visual correction. Anterior steep simulated keratometry (sim-K steep), corneal diameter (HVID), the Curvature at the apex in diopters (Cc), and distance from the corneal apex to the centre of the cornea (Lc) in millimetres derived from the Cone Location and Magnitude Index (CLMI) were recorded. Visual acuity, mean wearing time, final sagittal depth and adverse events were also recorded. Correlations between topographic indices and base curve were evaluated using the Pearson correlation coefficient. Results: Forty-six eyes from 26 patients (19 males/ 7 females) were included. Mean visual acuity improved from 0.49 +/- 0.32 with glasses, to -0.02 +/- 0.10 with the contact lens. The mean daily wear time was 12.19 +/- 1.96 hours. No complications were detected in 95.65% of the eyes [95% CI (83.9%-99.2%)] but two episodes of noninfectious keratitis. The average sagittal depth of the lenses fitted was 0.425 +/- 0.15 mm, and it was positively correlated with the Cc value (r(2) = 0.66, p < 0.0001, n = 46) derived from the CLMI index of the pre-fitting topography. Conclusions: Corneoscleral RGP contact lenses are a safe, and effective alternative for managing KCN patients to corneal lenses. Also, clinical data derived from the corneal topography could be used to help to decide the first diagnostic lens to be assessed, easing the overall fitting process.