Effect of lens diameter on lens performance and initial comfort of two types of GP lenses for keratoconus: a pilot study

Abstract

Purpose: The purpose of this pilot study was to determine the effect of varying lens diameter of two types of keratoconic lenses on lens performance and initial comfort with participants with either centered or oval cones. Methods: Sixteen eyes of ten keratoconic participants were fitted with lenses of five diameters i.e. 8.7, 9, 9.6, 10.1 and 10.4 diameters and two commercially available lens types; “KCGP-1” and “KCGP-2”. Lensmovement, centration and initial comfort were assessed. Results: Ten subjects (2 female and 8 male, sixteen eyes) were enrolled to participate in the pilot study, themean age was 40.4 ± 14.33 years. Six eyes were in the early centred cone group, five in the early oval cone group and five in the late oval cone group. The lenses with the 9.6 lens diameter (TD) decentered the least for all lenses (p = 0.001). When compared to cone type, the 8.7/9 were more decentered for the late oval and late centred cones (p = 0.009). The movement of the smaller KCGP-1 was greater than the KCGP-2 for the centered early cones (p = 0.001) and the movement decreased for the larger KCGP-2 lenses for all cone types but not significantly (p > 0.05). The KCGP-1 lenses were more significantly comfortable than the KCGP-2 lenses for the centered cones (p = 0.003). Only for the early oval cones, was the larger KCGP-2 lenses more comfortable (p = 0.04). Conclusions: Lens diameter affects comfort and centration especially for the small (8.7/9) and large (10.4/10.1) diameters in this pilot study. Lens movement was not correlated with comfort.

Keywords

• Keratoconus
• GP lens fitting
• GP lens diameter
• GP lens comfort