Eighteen dogs examined from April 1988 to March 1995 for complaints of total blindness or visual deficits were diagnosed with progressive rod-cone degeneration (PRCD) utilizing indirect ophthalmoscopy, tonometry, electroretinogram (ERG), and fluorescein angiography.
The animals were of the following breeds: 3 Maltese, 2 Pomeranians, 2 Toy Poodles, 2 Beagles, 2 mongrels, 1 Shetland Sheepdog, 1 Yorkshire Terrier, 1 Cavalier King Charles Spaniel, 1 Miniature Dachshund, 1 Chin, 1 Borzoi and 1 Shih Tzu.
The time owners became aware of visual abnormalities in their dogs ranged from 1 week to 2 years before the first examination. The following PRD signs were seen in all the dogs: a bilateral weakening or loss of pupillary light reflex in both eyes, mydriasis, attenuation of the retinal vessels, hyperreflectivity of the tapetal fundus, paleness of the optic disc, focal depigmentation of the nontapetal fundus, and low amplitude to non-recordable ERG. In other countries, progressive retinal degeneration is generally found in different breeds of dogs than those commonly affected in Japan. Our investigation showed that in Japan, the disease is mainly found in smaller sized dogs which are popular as pets. As PRD is thought to be a hereditary disease, systematic breeding programs and regular ophthalmologic examinations are necessary for prevention of the disease.
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