SUDDEN ACQUIRED RETINAL
SARD is a condition of middle-aged dogs in which there is a sudden onset of blindness without any other signs of eye disease. Some dogs show increased eating and drinking (and consequently urination), and some may have an underlying glandular disorder known as Cushings disease.
SARD is an incompletely understood condition and no effective treatment is available. Some researchers have suggested that the sudden loss of photoreceptor function, in which both rods and cones are affected, may be due to an excess of a neurotransmitter called glutamate. The increased levels of the excitatory chemical glutamate may 'switch off' the retina. Irreversible degeneration of retinal function follows.
Females and smaller breeds are more likely to develop SARD. The first indication that a dog may have SARD can be ravenous eating and drinking, or obvious evidence that sight is deteriorating rapidly, ie bumping into objects.
Diagnosis of SARD requires specialist veterinary ophthalmological examination. This involves a procedure called electroretinoscopy to assess the photoreceptive activity of the retina, which invariably progresses to zero.
Because this condition occurs occasionally in dogs with underlying disease, sometimes laboratory investigation, eg urine and blood tests, is warranted to eliminate such conditions.