A dachshund with "dayblindness" wears specially designed sunglasses
A genetic mutation in dachshunds could help uncover the roots of some inherited forms of blindness in humans, say scientists.
Cone-rod dystrophies are caused by progressive cell loss in the retina.
Dachshunds are particularly prone to similar conditions, and US and Norwegian researchers spotted an altered gene which may play a role.
Writing in the journal Genome Research, they said research on the similar gene in humans might lead to new therapies.
Cone-rod dystrophies are relatively rare, and can lead at first to "day-blindness", in which vision in bright light is affected, then to full loss of vision. It can start as early as childhood.
Other researchers have already identified genetic variations which seem to contribute to these conditions, but the latest research suggests that its genetic causes could be complex.
Inherited vision disorders are more common in dogs, and Dr Frode Lingaas of the Norwegian School of Veterinary Science isolated a particular part of a canine chromosome, and then a particular gene, called NPHP4, a portion of which had been deleted in affected dachshunds.
Dr Lingaas said: "This gene has been associated with a combination of kidney and eye disease in human patients.
"Here, we found a mutation which affects only the eyes, suggesting this gene might be a candidate for human patients with eye disease only."
He said that, even in the dog world, this could be a useful discovery, opening the way to genetic tests to help breed out some disorders.
However, he said the findings could make the development of human treatments easier.
Professor David Hunt, from the Institute of Ophthalmology, said that the finding could help scientists understand cone-rod dystrophies in some people.
Some, he said, were looking for ways to reverse similar conditions using gene therapy.
He said: "It is a wide spectrum of conditions, not just one.
"The problem is that there is a wide range of underlying defects and we haven't got a magic bullet which can target these all at once."
Sonal Rughani, from the Royal National Institute of Blind People, said: "This research is really exciting as it helps our understanding of the genetic basis of cone-rod dystrophies in humans.
"Following significant further research, this technique could facilitate the development of new treatments in the future."