To determine the impact of ultraviolet (UV)-absorbing silicone hydrogel contact lenses on the prevention of UV-induced pathological changes in the cornea, aqueous humor, and crystalline lens.
Twelve rabbits were assigned to one of three treatment groups (n = 4 per treatment group) as follows: 1) senofilcon A contact lenses (Acuvue Oasys, absorbs 99% of UV-B and 90% of UV-A); 2) lotrafilcon A contact lenses (Focus Night and Day, no UV absorption); 3) no contact lens. The contralateral eye was patched without a contact lens. Animals received UV-B (1.667 J/cm2) and UV-A (0.245 J/cm2) exposures daily for 5 days. Post-mortem tissues were examined as follows: in the cornea, expression of matrix-metalloproteinases (MMPs) was evaluated by zymography and apoptosis was evaluated by TUNEL and caspase-3 ELISA; ascorbate in the aqueous humor was evaluated by NMR spectroscopy; in the crystalline lens apoptosis was evaluated by TUNEL and caspase-3 ELISA. Non parametric statistical tests were used to compare outcomes accounting for treatment group and UV exposure status.
For the cornea, there was a statistically significant increase in MMP-2 and -9, TUNEL positive cells and caspase-3 activity in the UV-exposed lotrafilcon A group compared to the UV-exposed senofilcon A group (all p = 0.03). A statistically significant decrease in aqueous humor ascorbate was observed in the UV-exposed lotrafilcon A group (p = 0.03). For the crystalline lens, there was a statistically significant increase in caspase-3 activity in the UV-exposed lotrafilcon A group compared to the UV-exposed senofilcon A group (p = 0.03). There was also an increased number of TUNEL positive cells in both the UV-exposed lotrafilcon A and non-contact lens groups; this was not statistically significant compared to the UV-exposed senofilcon A group. There were no statistically significant differences noted in any of the outcomes when comparing the UV-exposed lotrafilcon A group and the non-lens wearing control group.
MMPs can be induced within the cornea by UV exposure and are associated with many pathologic inflammatory cascades. Ascorbate is a scavenger of free radicals in the aqueous humor and can decrease following UV exposure. DNA damage and apoptosis can be induced in both the cornea and lens by UV exposure. This is one of the first studies to show evidence that UV-blocking contract lenses are capable of protecting the cornea, aqueous humor, and crystalline lens from UV-induced pathological processes.
Vistakon, Division of Johnson & Johnson Vision Care Inc.