A slowly progressive retinopathy in the Shetland Sheepdog |
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| Authors: | Karlstam Lena Hertil Eva Zeiss Caroline Ropstad Ernst Otto Bjerkås Ellen Dubielzig Richard R Ekesten Björn |
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| Institution: | 1. Str?msholm Referral Hospital Str?msholm, Djursjukhusv?gen 11 SE‐734 94, Str?msholm, Sweden;2. University Animal Hospital, Swedish University of Agricultural Sciences, Uppsala, 7054 SE‐750 07, Sweden;3. Section of Comparative Medicine, Yale school of Medicine, 375 Congress Ave LSOG 114 New Haven, CT 06520, USA;4. Department of Companion Animal Clinical Sciences, Norwegian School of Veterinary Science, 8146 N‐0033, Oslo, Norway;5. Department of Pathobiological Sciences, University of Wisconsin, 3374 Veterinary Medicine Building 2015 Linden Dr Madison, WI 53706, USA;6. Department of Clinical Sciences, Swedish University of Agricultural Sciences, 7054 SE‐750 07 Uppsala, Sweden |
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| Abstract: | Objective To describe a slowly progressive retinopathy (SPR) in Shetland Sheepdogs. Animals Forty adult Shetlands Sheepdogs with ophthalmoscopic signs of SPR and six normal Shetland Sheepdogs were included in the study. Procedure Ophthalmic examination including slit‐lamp biomicroscopy and ophthalmoscopy was performed in all dogs. Electroretinograms and obstacle course‐test were performed in 13 affected and 6 normal dogs. The SPR dogs were subdivided into two groups according to their dark‐adapted b‐wave amplitudes. SPR1‐dogs had ophthalmoscopic signs of SPR, but normal dark‐adapted b‐wave amplitudes. Dogs with both ophthalmoscopic signs and subnormal, dark‐adapted b‐wave amplitudes were assigned to group SPR2. Eyes from two SPR2 dogs were obtained for microscopic examination. Results The ophthalmoscopic changes included bilateral, symmetrical, greyish discoloration in the peripheral tapetal fundus with normal or marginally attenuated vessels. Repeated examination 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 hyper‐reflectivity. The dogs did not appear seriously visually impaired. SPR2 showed significantly reduced b‐wave amplitudes throughout dark‐adaptation. Microscopy showed thinning of the outer nuclear layer and abnormal appearance of rod and cone outer segments. Testing for the progressive rod–cone degeneration ( prcd )‐mutation in three dogs with SPR was negative. Conclusion Slowly progressive retinopathy is a generalized rod–cone degeneration that on ophthalmoscopy looks similar to early stages of progressive retinal atrophy. The ophthalmoscopic findings are slowly progressive without tapetal hyper‐reflectivity. Visual impairment is not obvious and the electroretinogram is more subtly altered than in progressive retinal atrophy. The etiology remains unclear. SPR is not caused by the prcd‐mutation. |
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| Keywords: | dog electroretinogram progressive retinal atrophy retinopathy rod–cone degeneration Shetland Sheepdog slowly progressive retinopathy |
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