Cataracts in Ox: Causes of White or Cloudy Lens in Cattle

A cataract is an opacity within the lens, the clear structure behind the iris that helps focus light onto the retina. When the lens turns white, gray, or cloudy, light cannot pass through normally. That can reduce vision in one eye or both eyes. In cattle, cataracts may be present at birth, appear in young calves, or develop later after inflammation or injury.

It is important to separate a cataract from other causes of a white-looking eye. Corneal ulcers, pinkeye scars, uveitis, and severe corneal edema can also make the eye look cloudy from the outside. A cataract sits deeper inside the eye, so your vet usually needs a focused eye exam to tell where the opacity is coming from.

Not every cataract causes complete blindness. Small focal cataracts may be found incidentally during an exam and may never cause major handling problems. More mature cataracts can interfere with navigation, make cattle more reactive in unfamiliar settings, and sometimes trigger lens-induced inflammation inside the eye.

Cataracts in cattle are usually grouped by when they start and what triggered them. Some are congenital, meaning the calf is born with them. Congenital cataracts may occur as isolated developmental defects, as inherited problems in some family lines, or after fetal injury during pregnancy. In cattle, in-utero infection with bovine viral diarrhea virus has been linked to congenital ocular defects, including cataracts. Reports of congenital defects associated with transplacental viral infection also exist for other ruminant diseases such as bluetongue.

Other cataracts are acquired later in life. These can follow eye trauma, chronic uveitis, penetrating injuries, or severe inflammation elsewhere in the eye. Merck notes that cataracts in animals are often classified by age of onset, cause, and extent, and that spontaneous cataracts do occur in cattle, although complete blindness is considered uncommon in population studies.

Less often, cataracts may be associated with broader developmental eye abnormalities, retinal disease, or metabolic and nutritional problems. In practical herd medicine, your vet will usually think first about congenital change, prior inflammation, trauma, and infectious causes that could affect more than one calf.

Diagnosis starts with a full history and eye exam. Your vet will ask when the cloudiness was first noticed, whether one or both eyes are affected, if the calf was abnormal at birth, and whether there have been herd issues such as reproductive loss, weak calves, or known bovine viral diarrhea exposure. That context matters because a cataract can be an isolated finding or part of a larger congenital problem.

During the exam, your vet will determine whether the opacity is in the cornea, anterior chamber, lens, or deeper structures. This may include a menace response, pupillary light reflexes, focal light exam, fluorescein stain to check for ulcers, and tonometry if glaucoma or uveitis is a concern. Dilation may help your vet assess how much of the lens is involved and whether the back of the eye can still be seen.

If the lens is too opaque to view the retina, referral testing may include ocular ultrasound. In calves with suspected congenital disease, your vet may also recommend herd-level or individual testing for infections such as BVDV. Diagnosis is not only about naming the cataract. It is also about deciding whether the eye is comfortable, whether vision is functional, and whether there is a herd health implication.

Not every cataract can be prevented, especially congenital or inherited forms. Prevention focuses on reducing avoidable causes and catching herd-level problems early. Good biosecurity, a strong vaccination program designed with your vet, and BVD control are especially important because fetal infection can lead to congenital eye and brain defects in calves.

Protecting cattle from eye trauma and severe eye inflammation also matters. Prompt treatment of pinkeye, foreign bodies, and painful red eyes may reduce the chance of secondary damage inside the eye. Safe handling systems, reduced sharp hazards in pens, and lower dust and fly pressure can help support overall eye health.

If more than one calf is born with cloudy lenses, blindness, or other birth defects, involve your vet quickly. That pattern raises concern for infectious, toxic, or inherited causes. In those situations, prevention is less about one eye and more about herd investigation, breeding decisions, and pregnancy management.