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R. Whiting, R. Madsen, K. Narfstrom; Natural History of Hereditary Retinal Degeneration in Abyssinian Cats (rdAc). Invest. Ophthalmol. Vis. Sci. 2009;50(13):4507.
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Recessively inherited retinal degeneration in Abyssinain cats (rdAc) has been well characterized and a mutation in the CEP290 gene discovered. In preparation for therapeutic intervention, the time point for appearance of early functional changes in the retina was determined and the overall timeline for retinal degeneration assessed.
A total of 291 electroretinograms (ERGs), using scotopic and photopic recordings and standardized protocols, were performed in 97 anesthetized cats, aged 2.5 months to 9.5 years, using conventional Ganzfeld ERGs over a 7-year period. A- and b-wave amplitudes were measured, and the data was divided into deciles based on cat age at recording. Repeated measures analysis of variance was used to test for differences between affected and normal cats in ten age groups. The mean amplitude for each group was compared to that of the youngest age group (<5.5 months), differences were evaluated for significance, and the percentage of ERG parameter decline was calculated.
At scotopic high intensity stimulation (4 cd.s/m2), a significant difference (p<0.01) between normal and affected cats was found for all age groups for both a- and b-wave amplitudes. The table below shows mean decrease of a- and b-wave amplitudes in various affected groups compared to the youngest age group.
Affected Abyssinian cats have functional retinal changes much earlier than previously reported. A variable but progressive decline in a- and b-wave parameters was observed with 72% and 56% amplitude reductions for a- and b-wave amplitudes, respectively, in affected cats at age 4 years or older, when also showing clinical end-stage retinal degeneration.
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