In the retinas of human eyes, the cones are photoreceptor cells responsible for color vision, daylight vision, and the perception of small details. Vision scientists from the Division of Experimental Retinal Therapies at the University of Pennsylvania School of Veterinary Medicine, have been working for decades to identify the basis of inherited retinal diseases.
In dogs with three different kinds of naturally occurring retinal disease and in dogs with normal vision, the scientists used functional magnetic resonance imaging (fMRI) to assess brain responses to lights that stimulate only the cone photoreceptor (color-sensing) cells in the retina.
The researchers found that fMRI can detect brain responses to daylight vision for black and white information as well as color information, and it can identify the area of the visual cortex that responds to stimulation of a region in the dog retina that is rich in cones and similar to the human fovea. They also found they can use fMRI to measure the relative degree of loss of daylight vision. Using this technique in animals with a retinal disease caused by a mutation in a gene called NPHP5, they demonstrated that gene augmentation therapy restored the response in the cortex to black and white stimulation. That makes this disease a promising one in which to study photoreceptor cell replacement as a treatment in the future.