SARD = Sudden Acquired Retinal Degeneration

Below are several definitions/explanations collected through the research of Mrs. Marcia Feld.  They are printed here with her permission and with complete acknowledgement of their sources.

PLEASE BEAR IN MIND THAT THE MAJOR DIFFERENCE BETWEEN SARD AND PRA IS THAT PRA IS INHERITABLE - WHILE SARD IS NOT.

Sudden acquired retinal degeneration (SARD) is a recently described retinal disease of dogs that is characterized by an acute onset of blindness with an ophthalmoscopically-normal fundus.  Synonyms for SARD are "toxic metabolic retinopathy" and "silent retina syndrome."  Affected dogs are typically middle to old-aged, many of them are moderately overweight, and all breeds may be affected.  The primary complaint always is acute vision loss. Owners often report polyuria, polydipsia and polyphagia and, sometimes, night blindness (nycalopia).

Source: "Sudden Acquired Retinal Degeneration in the Dog "
Alexandra van der Woerdt, Mark P. Nasisse and Michael G. Davidson
Progress in Veterinary & Comparative Ophthamology/ Volume 1, Number 1 - pg 11
2. Sudden Acquired Retinal Degeneration (SARD)
This may be one disease or possibly several specific aging retinopathies.
Synonyms - silent retina syndrome, metabolic toxic retinopathy
Incidence
1. Older dogs - 6 to 14 years, average age 10 years
2. Breed predisposition - none
3. Sex - females more frequently seen
Etiology - unknown. Several theories have been proposed but no consistent finding has been identified.
Most animals are in good health but many have the complaint of polyphagia, weight gain, polyuria, and polydipsia.  However, this may be nothing more than a stress reaction to sudden blindness.
1. Cushing's disease
2. Immune-mediated
3. Neurotoxic reaction
History
1.  Sudden onset - 24 hours to several days.  After being questioned, many owners believe the dog may have had trouble several days before they realized it was totally blind.
2.   Nyctalopia may precede total blindness.
Examination findings:
1. Pupils dilated but will respond to bright light.
2. Dazzle reflex - absent
3. Fundus examination
a. Normal at onset; after several days may have subtle hyperreflective changes
b. After 30 days - signs of generalized degeneration are more obvious, but the changes seen are insufficient to account for the degree of blindness
c. Advanced cases will appear similar to generalized progressive retinal degeneration
4. ERG - absent
Treatment - none
Comment: Sudden blindness disorients older dogs more than young ones, but given time, most old dogs will usually become well adjusted pets.
Source: Severin: Ophthalmology Notes pg 449
Definition of SARD
Gretchen M. Schmidt, DVM, ACVO
S = Sudden: loss of vision over a period of days to weeks.
A = Acquired: not inherited, any breed or mixed breed at risk.  Some breeds seem higher, e.g. Miniature Schnauzer, Dachshund, Cairn Terrier
R.D. = Retinal Degeneration: death of photorecptor cells (rods and cones) in the retina. ERG is gone (flat line).  Lens brain, optic nerve, corneas not affected.
Cause unknown. Free radical theory?  Blindness frequently preceded by increased hunger, increased thirst, and weight gain.

Note:  Dr. Schmidt will be presenting on the topic of PRA/SARD at the 1999 National Specialty in Chicago.  This will be sponsored by the Chicago Miniature Schnauzer Club.