Optic nerve colobomas, whether inherited as CEA or acquired congenitally via embryologic aberration, are present at birth and do not progress.Īffected dogs’ vision will be altered to varying degrees (generally mildly and sometimes not at all). CEA is inherited as an autosomal recessive trait. Of these CEA dogs, an estimated 30% will suffer optic disc colobomas.įor the non-CEA associated form of optic nerve coloboma, there appears to be a hereditary predisposition in the Basenji breed. Other dogs may be affected by optic nerve colobomas though more rarely and sporadically. This includes both rough and smooth-coated collies, the Shetland Sheepdog, Australian Shepherd, Lancashire Heeler, and Border Collie. Up to 75% of Collies may be affected by CEA. In CEA, optic disc colobomas are but one of several potential problems observed in both eyes of affected dogs. In dogs, optic nerve colobomas can arise not only from a simple failure in embryologic development (which can be either genetic or environmental in origin and affect one or both eyes), but more commonly as a result of a genetic disease known as Collie Eye Anomaly (CEA). If the defect is large enough, normal nerve conduction related to vision can be disrupted and vision impairment ensues. We call this lesion an optic nerve coloboma. This creates a “pitted” or “cratered” area within or adjacent to the optic disc (where the optic nerve attaches to the eye). Should embryologic development not proceed normally, however, bits of the optic nerve may be left out of the process. The optic nerves located at the back of the eyes where they establish a direct connection to the brain are responsible for vision. Collie Eye Anomaly (CEA), also known as Optic Nerve Colobomas, is a disease of the dog’s optic nerve and more common in the collie breed.
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