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Bilateral aplasia of the optic nerve in a cat.

1974; BMJ; Volume: 58; Issue: 7 Linguagem: Inglês

10.1136/bjo.58.7.663

1468-2079

K. C. Barnett, T. Grimes,

Fetal and Pediatric Neurological Disorders

Congenital absence of the optic nerve in man is a very rare anomaly (Duke-Elder, I963, I964).In true cases the optic disc, optic nerve fibres, and central retinal blood vessels are absent on ophthalmoscopic examination.Hypoplasia of the optic nerve, which is also rare, occurs when some or all of the nerve fibres fail to develop and reach the disc.The condition may be unilateral or bilateral, and may be found in grossly malformed eyes or in those that are otherwise normal.Retinal vessels are present, however, although they may be greatly attenuated.The absence of retinal vessels necessarily involves a complete lack of vision.Hypoplasia of the optic nerve has been described in the horse (Gelatt, Leipold, and Coffman, i969), cattle (Leipold and Huston, i968), and dogs (Saunders, 1952; Gelatt and Leipold, 1971).Aplasia of the optic nerve has been recorded in the cat ((Abderhalden, 1903; Zeeman and Tumbelaka, I9I6; Szymanski, I926; Veenendaal, 1936) and the mouse (Bein, 1947).This report records the ophthalmoscopic and pathological features of bilateral aplasia of the optic nerve in a cat. Case reportA 5-week-old male black-and-white long-haired kitten presented with a history of total blindness.It was one of a litter of three born on a farm.The dam and two littermates were examined and found normal.The sire was unknown.The dam had produced several previous litters with no ap- parent abnormalities.This kitten was well grown and, except for the ocular defect and a stumpy tail, was normal.Hearing was acute and when the animal was moving there was continouus and rapid head shaking.Ocular movements were few but there were intermittent episodes of nystagmus, both vertical and horizontal, rapid, of small excursion, and apparent only on ophthalmoscopic examination.The two eyes were similar and normal in size (Fig. I).The ocular adnexa and the anterior segment, including the lens, were normal.The pupils were dilated, circular in shape, and did not respond to light.When the animal was active the pupils were maximally dilated but they constricted slightly at rest and exhibited hippus.In sleep the pupils were constricted and of the normal feline vertical slit shape.FIG.I Two eyes similar, normal in size, dilated pupils