Hemeralopia (day blindness), is an abnormal opthalmic disease characterized by blurred vision when a dog is exposed to bright light.
Although this condition may be an acquired condition with hyperadrenocorticism, use of certain seizure medications (e.g. vigabatrin) and following cataract-removal surgery, it is normally an autosomal-recessive condition caused by retinal degeneration associated with a number of conditions including:
- Progressive retinal atrophy
- Retinal pigment epithelial dystrophy
- Congenital stationary night blindness
- Cone degeneration
- Progressive rod cone degeneration
in clinically affected dogs, day blindness is apparent by eight to ten weeks of age. Night vision is rarely if ever impaired. Hemeralopic dogs show severe loss of vision both in daylight and in high levels of artificial illumination, but such dogs become less insecure when placed in dim lighting. Recovery of vision takes several minutes, though loss of vision on returning to bright light is immediate.
Histologic and ultrastructural studies of the retina indicate that in the mature hemeralopic dog there are no identifiable cones, and that in the younger dog (six months of age), normal cones do not exist, although degenerate cones can be found. In all hemeralopic dogs, the rods and the inner retinal layers of the eye are normal.
In most cases, here is no effective treatment for hemeralopia, although gene therapy shows promise.
- Merck Vet Manual
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