Full-field electroretinograms in miniature poodles with progressive rod-cone degeneration.

Full-field electroretinograms (ERGs) were recorded between the ages of 4 and 34 months from 8 miniature French poodles with inherited progressive rod-cone degeneration (PRCD) and from 11 normal miniature poodles. Three stages of retinal function were observed in the affected dogs, although the ages of transition from one stage to the next were variable among dogs. Rod and cone ERGs were normal in amplitude in the first stage, rod ERGs were reduced in amplitude and cone ERGs were normal in the second, and rod ERGs were extremely reduced in amplitude or nondetectable and cone ERGs were reduced in amplitude in the third. On average, these poodles with PRCD lost 7.2% of remaining rod amplitude per month and 2% of remaining cone amplitude per month. Affected poodles had normal rod and cone b-wave implicit times over all three stages, in contrast to humans with the early stages of progressive forms of retinitis pigmentosa who have delayed rod and/or cone b-wave implicit times.