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Retinal folds and retinal dysplasia
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Елена:
Diagram from The National Eye Institute
http://www.nei.nih.gov/health/eyediagram/
ETIOLOGY
Retinal folds and retinal dysplasia are closely related eye diseases that are primarily inherited, suspected to be autosomal recessive. Other causes include toxicity and infections during pregnancy, including herpesvirus and possibly parvovirus. These diseases are found in bichons, although not frequent among our breed compared to some other breeds. CERF reports for the last 12 years cite 43 cases in bichons, but this does not account for the majority of bichons who do not undergo annual CERF examination. Because these diseases may cause blindness in puppies, bichon breeders need to be aware that we should not be breeding affected bichons, and of course we should all CERF our breeding stock.
PATHOPHYSIOLOGY
The retina is a layer of sensory tissue that is attached to the tissue in the back of the eye. The retina receives light stimuli from the environment and converts it to an electric signal that is sent to the brain via the optic nerve, which lies behind the retina. The brain interprets this signal and vision occurs. Any alterations in the retinal tissue can impair vision. The retinal tissue undergoes changes until the eye is fully developed at the age of one year.
Dysplasia is defined as abnormal growth or development. Retinal dysplasia forms when the 2 developmental layers of the retina do not unite properly. It can involve both eyes or one, but the inherited form is almost always bilateral. It can occur anytime during eye development, from pregnancy to one year of age. There are 3 forms of retinal dysplasia:
Focal retinal folds: These are wrinkles in the retinal tissue in one or more areas. They cause small blind spots, but rarely cause visual impairment for the dog. They primarily occur in young dogs with developing retinas, and usually disappear by the age of one year. Young dogs (
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