Progressive retinal atrophy (GUCY2D-PRA)

Progressive retinal atrophy (PRA) is a leading hereditary cause of blindness in pedigree dogs as is its counterpart retinitis pigmentosa (RP) in humans. PRA shows genetic heterogeneity, as does RP, with several distinct forms already recognized and several more remaining to be investigated. One can distinguish between late onset forms of PRA and early onset (whelp-age) dysplastic changes. The clinical and ophthalmologic signs of both forms are similar. Affected dogs suffer from bilateral Mydriasis, the reflection of the Tapetum lucidum is increased and the retinal vascular network appears atrophic.

A genetic variant of the GUCY2D gene has been found to be associated with an early-onset PRA in the breed German Spitz. Affected dogs suffer from impaired vision under both scotopic (dim light) and photopic (bright light) conditions, already noticeable at the age of 3 months. They show pale papilla and mild vascular attenuation. Some of them also have oscillatory nystagmus. While the photoreceptor function is already severely impaired or absent after a few months of age, the retinal structure is initially well-preserved. Only in older affected animals, a slight retinal thinning could be observed.