Ultraviolet A absorption coefficients of contact lenses for use in contact lens assisted corneal crosslinking for thin Corneas

The purpose of this study was to compare the UVA absorption coefficients of multiple hydrogel and silicone hydrogel lenses (with and without pre-soaking in riboflavin) to those reported for the human cornea. The study also assessed the effect of different contact lens pre-soak times (in riboflavin) on the measured UVA absorption coefficients. Five lenses each of Omafilcon A, Nelfilcon A and Somofilcon A were pre-soaked in riboflavin and UVA absorption was assessed. Six lenses each of two hydrogel (Omafilcon A and Nelfilcon A) and three silicone hydrogel (Comfilcon A, Lotrafilcon A, and Samfilcon A) lenses were assessed before and after a 30-minute soak in riboflavin. One-way ANOVA was used for all comparisons. Absorption coefficients, without riboflavin, for Omafilcon A, Nelfilcon A and Somofilcon A were: 8.6 ± 1.2 cm^-1; 11.7 ± 3.4 cm^-1; 51.9 ± 2.9 cm^-1, respectively. These absorption coefficients were all significantly greater (p < 0.0001) after pre-soaking in riboflavin. The average (+/- SD) coefficients of the different lenses in the main study, without riboflavin, were: 9.1 +/- 0.7 cm-1; 10.9 +/- 2.1 cm-1; 6.9 +/- 2.0 cm-1; 16.2 +/- 2.8 cm-1; and 17.8 +/- 3.2 cm-1, respectively, for: Omafilcon A; Nelfilcon A; Comfilcon A; Lotrafilcon A; and Samfilcon A. Absorption coefficients were all significantly greater (two-tailed, paired Student's t-test, p < 0.0001) with riboflavin. Oxygen permeability is a better predictor of the absorption coefficient (and therefore of the contact lens-assisted corneal collagen crosslinking effectivity) of a soft contact lens than water-content.