Lenses from Brown‐Norway pigmented rats are more tolerant to in vitro ultraviolet irradiation than lenses from Fischer‐344 albino rats

Purpose: To investigate if the previously shown difference in in vivo‐induced ultraviolet B radiation (UVR‐B) cataractogenesis between pigmented and albino rats can be seen also with in vitro irradiation. The shielding effect of the iris and UVR absorption in the anterior segment is nullified, and inherent differences in lenticular UVR‐B sensitivity between the strains may be revealed. Methods: Lenses from albino (Fischer‐344) and pigmented (Brown‐Norway) rats were irradiated in vitro with 1.8 kJ/m² UVR‐B. The lenses were cultured in standard environment in a culture incubator. Cataract was quantified daily by measuring the amount of lens forward light scattering over a period of 1 week. All lenses were photographed during the week. Results: Two days after exposure, both strains developed significant cataract compared to control lenses, and the light scattering increased exponentially to the last day. From day 4, exposed Fischer lenses scattered more light than Brown‐Norway lenses. This difference increased towards the end of the week. The type of cataract (anterior subcapsular, equatorial, and posterior cortical cataract) was similar in both strains. No anterior polar or nuclear cataract was observed. Conclusions: Lenses from albino Fischer rats are more sensitive to in vitro UVR‐B than lenses from pigmented Brown‐Norway rats. Ultraviolet B radiation cataract type induced in vitro differs from in vivo cataract in pigmented rats, but not from albino rats. In vitro UVR‐B exposure induces more cataract than corresponding lenticular UVR‐B in vivo exposures, for both albino and pigmented rat.