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MK Kakar, VC Mody Jr, S Lofgren, X Dong, PG Soderberg; Evolution of Ultraviolet Radiation-B (UVR-B) Induced Cataract in the Pigmented Rat . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3573.
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Purpose:To investigate cataract development in pigmented rats as a function of time after acute exposures to UVR-B doses of 5 kJ/m2 and 25 kJ/m2. Methods:One hundred and sixty pigmented Brown Norway rats 6 weeks old, were divided into 8 equal groups. After anesthesia with ketamine (45mg/kg) and xylazine (10 mg/kg), pupils were dilated bilaterally with 1% tropicamide. After another 10 minutes, the eyes were unilaterally exposed to either 5 or 25 kJ/m2 UVR-B over 15 minutes. For each dose, the rats were sacrificed after 5, 25, 125, or 625 hrs. Both eyes were enucleated and lenses were extracted. Following this, the intensity of forward light scattering was measured in a cuvette for each of the lenses immersed in balanced salt solution. Photographs were then taken with a photomicroscope. Statistical analysis was performed with significance level set at 0.05 and confidence coefficient of 0.95. Results:Following exposures to 5 kJ/m2, the intensity of forward light scattering increased till 125 hours post-exposure and decreased thereafter. Microscopic examination of the exposed lenses revealed a pattern of diffuse anterior capsular haze progressing to faint anterior subcapsular opacities and eventually indistinct shell-shaped opacities in extranuclear region. In contrast after exposure to 25 kJ/m2, intensity of forward light scattering peaked at 5 hours post-exposure and decreased thereafter. Cataract development after 25 kJ/m2 followed a trend of diffuse anterior capsular haze with posterior cortical involvement, recovering to distinct anterior subcapsular opacities and finally shell-shaped opacities in the extranuclear region. Also, exposure to 25 kJ/m2 induced higher intensities of forward light scattering in the lenses when measured at similar time points. Conclusion:Progression and repair of the UVR-B cataract is dose dependent. Cataract development occurs more rapidly at higher doses in the pigmented rat. The pigmented Brown Norway rat is less sensitive to similar doses of UVR-B compared to the albino Sprague Dawley rat.
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