Retinal degenerations

The retina is the nerve tissue at the back of the eye which when stimulated by light sends electrical impulses to the brain which are interpreted as vision. Patients may develop a number of potentially vision affecting or destroying diseases of the retina. These can be inherited or acquired.

PRA – Progressive retinal atrophy: is an inherited disease causing progressive irreversible vision loss. The majority of affected patients are purebred dogs, where the inheritance is most commonly “autosomal recessive”.  This means that the affected patient needs 2 bad genes for blindness to occur (one from both parents, thus both parents must be at least carriers of the disease).

The first sign usually noticed by the owners is poor night vision, which progresses over months to include day vision loss. DNA testing to screen for clear, carrier or affected status of patients and potential breeding animals is becoming more available. Many breeders of purebred dogs have there breeding animals eyes checked annually by an ophthalmologist to check for the occurrence of this and other inherited eye diseases.

SARD – Sudden Acquired Retinal Degeneration is a non-inherited irreversible sudden vision loss with no history of exposure to toxins, trauma or other disease. Excepting for the vision loss and usually dilated pupils, the eye examination reveals no obvious abnormalities.  Electrical retinal testing (ERG) is very helpful in diagnosing SARDs.