Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

Collie eye can be detected by a veterinary ophthalmologist in puppies as
young as 4 to 8 weeks of age, after the bluish puppy film disappears from the
eye. The retina is graded 1 to 5, depending on the degree of degeneration.
Grades 1 and 2 do not affect eyesight; grades 3, 4, and 5 are associated with
increasing visual impairment. The grade does not change as the dog grows
older, but retinal detachment with sudden blindness can occur at any time.
There is no treatment.
Prevention: The inheritance of Collie eye anomaly has been investigated
in the breed and found to be a simple recessive genetic trait. Genetic tests
from OptiGen are now available for Collie eye anomaly in many of the
affected breeds.
PROGRESSIVE RETINAL ATROPHY
THE EYES • 203
Progressive retinal atrophy (PRA; also known as PRCD, progressive rod and
cone degeneration) was first discovered in the Gordon Setter in 1911 and is
now recognized in more than 86 breeds. PRA includes several specific inherited
types of the diseases. In most instances the mode of inheritance is an
autosomal recessive gene. In all cases there is destruction of retinal cells in
both eyes, leading to blindness. There is no treatment for PRA.
The initial sign of PRA is night blindness. The dog hesitates to go out at
night and won’t jump on or off furniture in a dark room. As vision loss progresses,
the dog develops other signs of impairment. For example, the dog may
go up but not down a flight of stairs. Other behavioral changes also suggest
loss of vision.
Early onset slow progression PRA causes night blindness during the first
year of life but dogs may retain daylight vision for a year or longer. Breeds
affected by this type of PRA include the Akita, Miniature Schnauzer,
Norwegian Elkhound, Tibetan Terrier, Dachshund, and Gordon Setter.
Early onset rapid progression PRA causes visual impairment beginning
during the first year of life and progressing to complete blindness in a matter
of months. Breeds affected by this type include the Collie, Irish Setter, and
Cardigan Welsh Corgi.
Late onset PRA causes night blindness that is noted after 2 years of age.
Complete blindness occurs by age 4. This variant affects the Afghan Hound,
Border Collie, Cocker Spaniel, and Labrador Retriever.
Sudden acquired retinal degeneration is a disease of unknown cause found
most often in healthy, middle-aged female dogs 6 to 14 years of age. It produces
rapid and complete loss of vision in both eyes in a matter of hours to several days.
An electroretinogram (ERG), which measures the retina’s response to light
using a corneal electrode and neutral electrodes placed on the skin around the
eye, may be done to definitively diagnose PRA after a CERF exam has suggested
this diagnosis.