Anophthalmos (anophthalmia); microphthalmos (microphthalmia)

Clinical features

the two examples illustrate both abnormalities. The left eye of the Guernsey heifer in 8.2 has a small orbit and there is no evidence of the globe. Note that the entire orbit appears collapsed and smaller, compared with the normal right eye. This condition can be inherited. A Jersey cow with microphthalmos (8.3) and prolapse of orbital fat had possibly had an insult to the eye in calfhood, leading to this shrunken globe (phthisis bulbi).

8.2 Anophthalmos in left eye of heifer (Guernsey)

8.3 Microphthalmos in cow (Jersey)

Cataract

Clinical features

both eyes of the 4-day-old Hereford crossbred calf in 8.4 were affected and the animal was totally blind. In other animals, only one eye may be affected, or the cataract may not cause total loss of vision. Congenital cataract is not normally progressive. Cattle cope with blindness remarkably well and can be reared in confinement systems. They quickly learn to remain within the group, although handling can be difficult. Blind dairy cows will learn to follow the herd to and from pasture. Congenital cataract may be inherited, or may result from the teratogenic effects of maternal BVD infection during early/mid pregnancy. 8.5 shows a congenital nuclear cataract in a young Friesian calf.

8.4 Cataract, bilateral, (Hereford cross, 4 days old)

8.5 Congenital nuclear cataract in calf resulting from maternal BVD infection (Friesian)

Note in acquired cataract the two large synechiae (adhesions of the iris to the cornea), and the opacity and wrinkling of the lens in the Guernsey cow in 8.6. Cataracts may be secondary to inflammatory processes within the eye, when they can be progressive. In contrast, congenital cataracts (8.4) are rarely progressive.

8.6 Acquired cataract in cow (Guernsey)

Coloboma

Clinical features

it can occur in the eyelids, iris, lens, or, as shown in 8.7, the retina. Note the pale area devoid of functional retinal cells. The condition is inherited in certain breeds of cattle (e.g., Charolais), but vision is not normally impaired.

8.7 Coloboma involving retina in cow

Dermoid

Clinical features

a typical dermoid is seen in a 4-month-old Friesian heifer (8.8). The tumor is attached to the conjunctiva of the lower lid and presents long hairs, which led to the presenting sign of unilateral epiphora.

8.8 Dermoid attached to conjunctiva in heifer (Friesian, 4 months old)

Strabismus (“squint”)

Clinical features

strabismus may be convergent (esotopia), when the visual axes of the eyes converge more than is required for normal vision, or divergent. It may involve one or both eyes. The globe is deviated from its proper axis due to excessive tension in opposing extraocular muscles. 8.9 shows convergent strabismus in the left eye of a Hereford cross heifer. Exophthalmos with strabismus may be inherited, although it is often unnoticed until 6–9 months old, and it is frequently progressive. Some animals may become so badly affected that total impairment of vision results.

8.9 Convergent strabismus (“squint”) in heifer (Hereford cross)

Neonatal corneal opacity

A reduction in intraocular pressure in stillborn calves leads to cloudiness in the cornea and indicates that the calf has died at least 12 hours before birth. In the stillborn Charolais calf in 8.10 the eyeball is also slightly sunken in the socket.

8.10 Neonatal corneal opacity in stillborn calf (Charolais)

Vitamin A deficiency

In young growing animals, vitamin A deficiency blindness is associated with stenosis of the optic foramen and consequent pressure on the optic nerve. The pupil becomes dilated and degenerative changes may be seen on the retina (8.11). For comparison, 8.12 shows a normal fundus. The optic disc is pale and enlarged, with indistinct margins (papilledema). White mottling of the nontapetal area suggests chorioretinal degeneration. The steer was blind. The diet had been barley straw, rolled barley and, occasionally, poor-quality hay.

8.11 Vitamin A deficiency: degenerative changes in retina (blind steer) (Canada)

8.12 Normal fundus