Rod-cone dysplasia (progressive retinal atrophy) in Irish setters
Aguirre, G.D.; Rubin, L.F.
Journal of the American Veterinary Medical Association 166(2): 157-164
1975
ISSN/ISBN: 0003-1488 PMID: 1112740 Document Number: 90416
Two pups, one bred from a couple known to be carriers of the retinal atrophy defect and the other from an affected male and its carrier dam, were examined for the development of degenerative changes in the eyes. Ophthalmoscopy revealed no abnormality of the fundus between 24 days and 6 weeks of age. By week 14, abnormal granular appearance of the tapetal retina was seen. By month 4, the granulation continued with extensive hyperreflectivity which varied in intensity at any given area. There was also narrowing of the small vessels in the retina. By month 6, the hyperreflectivity had increased and the vascular narrowing progressed further. The latter change occurred in the non-tapetal zone as well, but the pallor of the non-tapetal fundus was barely perceptible. By electroretinography (ERG) rod-mediated responses could not be recorded. Abnormal cone-mediated responses were recognizable at 24 days, 6 weeks and 14 weeks of age. These responses deteriorated thereafter and by 181/2 weeks of age ERG was almost extinguished. By light microscopy abnormalities characterized by narrowing of the receptor outer nuclear layer and pyknosis of rod nuclei were evident by 24 days of age. Abnormalities recorded above were not detected in carrier dogs or the littermates of affected dogs; the former, however, showed disturbance in the photoreceptor system by ERG. It was concluded that in affected dogs, rods and cones degenerated without attaining functional maturity [see also VB 41, abst. 4204 and VB 42, abst. 4081].