To see whether the fovea-like region was similarly affected in dogs, the Penn researchers used the same techniques they had employed to study normal dogs to examine animals that had mutations in two genes (BEST1 and RPGR) that can lead to macular degeneration in humans.
In both cases, the onset of disease affected the fovea-like region in dogs in a very similar way to how the diseases present in humans -- with central retinal lesions appearing earlier than lesions in the peripheral retina.
"Why the fovea is susceptible to early disease expression for certain hereditary disorders and why it is spared under other conditions is not known," Cideciyan said. "Our findings, which show the canine equivalent of a human genetic disease affecting an area of the retina that is of extreme importance to human vision, are very promising from the human point of view. They could allow for translational research by allowing us to test treatments for human foveal and macular degenerative diseases in dogs."
In addition, the discovery offers insight into a rare human condition known as fovea plana, in which people have normal visual acuity but no "pit" in their fovea. In other words, their fovea resembles that of dogs, challenging the previously held assumption that lack of tissue and blood vessels overlaying the fovea is a prerequisite for the high resolution of vision.
The fact that dogs have a fovea-like area of dense photoreceptor cells may also indicate that dogs are seeing more acutely than once suspected.
"This gives us a structural basis to support the idea that dogs might have a higher visual acuity than has been measured so far," Beltran said. "It could even be the case that some breeds have an especially high density of cells and could be used as working dogs for particula
|Contact: Katherine Unger Baillie|
University of Pennsylvania