Complete (agenesis) or partial (coloboma) absence of all the eyelid layers, or some of the eyelid layers may affect one or both eyes. It is the commonest congenital eyelid abnormality of cats, boith domesticated and wild . The region most frequently affected is the lateral part of the upper eyelid, but occasionally the medial and lateral canthus is involved. Rarely, the centre of the eyelid is involved. Multiple ocular colobomas in the Snow Leopard were first recorded in 1978 and there have been subsequent reports since.
No specific aetiology has been established, although a number of possibilities, including teratogenicity, environmental influences and genetic predispositon have been suggested. Ocular manifestations range from single defects (eyelid coloboma) to multiple ocular defects (eyelid colobomas, microphthalmos, cataract, retinal dysplasia, choroidal and optic nerve colobomas). Similar multiple congenital ocular anomalies have been reported in domestic short hair kittens.
A genetic predispostion to incomplete development of the eyelids at the lateral and medial canthus is suspected in certain lines of Burmese cats and epibulbar dermoids may also be part of the developmental defect in this breed.
- Bellhorn, RW, Barnett, KC, Henkind, P (1971) Ocular colobomas in domestic cats. Journal of the Amwerican Veterinary Medical Association 159:1015-1021
- Barnett, KC & Crispin, SM (2002) Feline Ophthalmology: An atlas & Text. p: 35 Elsevier Ltd
- Martin, CL, Stiles, J, Willis, M (1997) Feline colobomatous syndrome. Veterinary and Comparative Ophthalmology 7:39-43
- Koch, SA (1979) Congenital ophthalmic abnormalitites in the Burmese cat. JAVMA 174:90-91