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B. A. Ekesten, L. Karlstam, C. J. Zeiss, R. R. Dubielzig; A Slowly Progressive Retinal Degeneration in the Shetland Sheepdog. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3645.
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© ARVO (1962-2015); The Authors (2016-present)
To study a spontaneously occurring, slowly progressive retinal degeneration (SPRD) in related Shetland Sheepdogs (Shelties) in Sweden.
Shelties were routinely screened for hereditary eye diseases in a health program. The examination included direct and indirect ophthalmoscopy and slit-lamp biomicroscopy after dilating the pupils with tropicamide. Electroretinograms (ERGs) were performed under isoflurane anaesthesia in 12 dogs with SPRD and 6 normal Shelties. One Sheltie with abnormal ophthalmoscopic appearance and abnormal ERG was euthanized and the eyes were examined by light-microscopy.
Ophthalmoscopic examination revealed bilateral, grayish, hyporeflective areas in the peripheral and midperipheral tapetal fundus with either normally appearing retinal vessels or slightly attenuated peripheral vessels in 39 related Shelties (16 males, 23 females; aged 2.5-13 years) between 2001-2009. The hyporeflective areas were symmetrically distributed between the eyes. Re-examination of 15 dogs after 6 months to 4 years showed that the ophthalmoscopic changes slowly spread across the central parts of the tapetal fundus, but did not progress to obvious neuroretinal thinning presenting as tapetal hyperreflectivity and did not cause obvious visual impairment. The ERGs of SPRD dogs either fell within normal limits (4 dogs) or showed subnormal, marginally delayed rod responses, whereas the cone responses were essentially normal (8 dogs). Thinning of the outer nuclear layer and photoreceptors displaced into the subretinal space were seen on light-microscopy. DNA-testing for prcd/PRA in 3 dogs with SPRD was negative.
We describe a slowly progressive retinal degeneration in a group of related Shelties in Sweden. The appearance of the tapetal fundus in SPRD is similar to early-stage progressive retinal atrophy (PRA). The slow progression and recordable rod ERGs in old dogs clearly show that this is different from prcd/PRA. The condition is likely to be inherited given the close kinship between the affected dogs.
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