Abstract
Purpose: :
UVB radiation from sunlight is known to be a risk factor for human cataract. The purpose here was to investigate the ability of a Class I (Senofilcon A) soft contact lens to protect against UVB-induced damaging effects on the rabbit lens and cornea in vivo.
Methods: :
Eyes of rabbits were irradiated using a bank of UV lamps (UBLF20T12/UVB) at a distance of 7.5 cm (Andley et al., IOVS, 1996). The maximum intensity of the light was at a wavelength of 310 nm, with a spectral distribution of 270-360 nm, and irradiance on the cornea of 1.7 mW/cm2. Eyes containing either a senofilcon A contact lens, a non UV-absorbing contact lens, or no contact lens at all, were irradiated for 30 min to produce a total fluence of 3J/cm2, equivalent to 16 hr of maximum exposure of the human cornea to UVB radiation from sunlight. Effects on the corneal epithelium were evaluated after 12h using fluorescence staining and histology. Effects on the lens and lens epithelium were evaluated after 48h by slit lamp examination, cell viability staining, transmission electron microscopy (TEM) and single cell gel electrophoresis (the latter measured DNA single strand breaks in lens epithelium).
Results: :
Severe loss of corneal epithelial cells was observed 12h after irradiation of eyes with no contact lens protection. The senofilcon A contact lens provided complete protection against UVB-induced loss of corneal epithelium, whereas the non UV-absorbing contact lens provided no protection. Slit lamp examination showed extensive anterior subcapsular opacification in eyes irradiated with no contact lens protection. The senofilcon A contact lens protected completely against UVB-induced lens opacification; however, the non UV-absorbing contact lens showed no protection. TEM analysis showed substantial lens epithelial cell swelling, vacuole formation, nuclear fragmentation and chromatic condensation in eyes irradiated without the presence of a contact lens. The senofilcon A contact lens completely protected against this damage, whereas the non UV absorbing lens showed no protection. Similar results were obtained regarding UVB-induced death of lens epithelial cells and UVB-induced DNA single strand breaks in lens epithelial cells. In both cases, the senofilcon A contact lens showed complete or nearly complete protection against UVB-induced effects, whereas the non UV absorbing lens offered no protection. Results will also be presented regarding UVA-induced effects on the rabbit lens in vivo with and without senofilcon A contact lens protection.
Conclusions: :
The senofilcon A contact lens is highly protective of the lens and cornea against UVB-induced damage in vivo, including lens opacification.
Keywords: radiation damage: light/UV • cataract • contact lens