Purpose To conduct ophthalmic, behavioral, electrophysiological, and genetic testing on two related Gordon setters presented for day blindness and compare findings with those of nine related and unrelated Gordon setters. Methods All dogs underwent comprehensive ophthalmic examination. Maze testing was conducted under different light intensities. Rod and cone function was assessed electroretinographically. DNA samples were screened for five canine retinal disease gene mutations. Results Ophthalmic examination was unremarkable in all dogs. There was no notable difference between day blind dogs and the reference population in scotopic and meso-pic maze tests. Day blind dogs performed worse in the photopic maze with slower course completion time and more obstacle collisions. Electroretinography revealed extinguished cone function in day blind dogs and depressed rod responses in all but two reference dogs. One reference population dog presented with day blindness 1 year after initial examination. Mutations that cause achromatopsia (in CNGB3) and cone-rod dystrophies (in ADAM9 and IQCB1) were not detected in any dog tested, although five reference dogs were carriers of the mutation in C2orf71 that causes rod– cone degeneration 4 (rcd4) in Gordon setters and in polski owczarek nizinny dogs. Conclusions This report describes a novel retinopathy in related Gordon setters that has clinical signs and vision testing results consistent with achromatopsia but electroretinographic results suggestive of cone-rod dystrophy. The majority of Gordon setters in this study had low rod responses on electroretinography but it is unclear whether this was indicative of rod dysfunction or normal for the breed. Longer-term observation of affected individuals is warranted.
Bibliographical noteFunding Information:
The authors are extremely grateful to the Gordon setter breeders and owners who kindly allowed their dogs to participate in this study. We also thank Drs. Deborah Friedman and Ann Gratzek for their initial referral of the probands, and C. Yeh (University of Pennsylvania and Michigan State University) and S. Pearce-Kelling (Optigen, LLC) for their assistance with DNA analysis. A special thank you to Dr. Rebecca Burwell for examining one of the dogs at the 1.5-year follow-up evaluation, Dr. Raaya Ezra-Elia for her help with the ERG traces, Dr. David Maggs for manuscript review, and Dr. Sara Thomasy and John Doval for their help with graph and pedigree illustrations, respectively. This study was funded in part by NIH grant RO1-EY019304.
© 2015 American College of Veterinary Ophthalmologists.
- Cone-rod dystrophy
- Day blindness
- Night blindness