Testing for PRA
Diagnosis of PRA can be made by ophthalmoscopic examination. This requires dilatation of the pupil by application of eyedrops. PRA can be diagnosed by ophthalmoscopic changes:
- increased reflectivity (shininess) of the fundus (the inside of the back of the eye, overlain by the retina)
- reduction in the diameter and branching pattern of the retina's blood vessels
- shrinking of the optic nerve head (the nerve connecting the retina to the brain).
There is also a DNA test available for the rdAc mutation, which is causing the most common PRA.
The benefit with a DNA test for PRA is that we can find affected cats before they show symtoms. A cat with double set of this recessive gene (the rdAc) will develop PRA, although there may be no signs at an ophthalmoscopic examination.
The advantage with the ophthalmoscopic examination is that you could also find other types of PRA than the one caused by the rdAc mutation, and you could find signs of other eye diseases as well.