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Yumiko Umino, Eduardo Solessio; Loss of Scotopic Visual Sensitivity in Diabetic Mice. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5958.
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Diabetes leads to early dysfunction of photoreceptors and neurons in the inner retina. However the effects on visual function are not well understood. Our goal was to determine if diabetes induces early visual losses in the Ins2Akita/+ mouse model of type 1 diabetes.
Age-related changes in contrast sensitivity of Ins2Akita/+ diabetic mice and their littermate controls were measured using a visuomotor behavioral assay (OptoMotry®, CerebralMechanics Inc). Spatial and temporal contrast sensitivity functions were determined in dim light conditions and in bright light conditions to study rod- and cone-driven visual sensitivities, respectively.
In Ins2Akita/+ mice the onset of diabetes (defined as blood glucose > 500 mg/dL) occurred at 5 weeks whereas the decline in sensitivity began after 10 weeks of age. Mice experienced a loss in sensitivity to gratings with wide bars (low spatial frequency) presented in dimly lit environments, indicating a loss in rod-driven (scotopic) vision. Visual sensitivity decreased progressively with time, and steadied at approximately 50% of its initial value after 20 weeks. Sensitivity to gratings with narrow bands (high spatial frequencies) did not change significantly, suggesting that acuity remained unaltered. Our preliminary studies in bright backgrounds suggest that cone-vision (photopic) sensitivity does not change during the first 34 weeks of age.
We identified an early, progressive loss of visual contrast sensitivity in the Ins2Akita/+ mouse. This unexpected finding involves rod vision (dim lights, achromatic vision) rather than cone vision (bright lights, color). The loss in contrast sensitivity suggests dysfunction of neural circuits that compute light differences across the retinal image (contrast) rather than impaired rod and cone photoresponses.
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