Gunbil German shepherd puppy in motion

A cataract is the clouding or loss of transparency of the lens. The lens of the eye is the critical focusing component of the eye. When it becomes opaque or cloudy, enough light may not pass through it and your pet’s vision may be impaired. Cataracts cause the pupil to appear grey or white.

Cataracts are often confused with nuclear sclerosis, or the normal aging of the lens, which does not usually affect vision and is commonly seen in older dogs. Cataracts can be genetically predetermined or have other secondary causes. Currently, there is no way to test for genetic predisposition. Secondary causes include uveitis and diabetes mellitus.

Clinical Signs

The most common clinical sign of cataracts is the appearance of a white or grey color behind the pupil. Other clinical signs include partial or total loss of vision and avoidance of dark rooms or hallways.


Your veterinarian can diagnose cataracts using an opthalomoscope. By determining how much of the lens is affected, your veterinarian may be able to determine how impaired your pet’s vision may be.


If the cataract is secondary to another disease, treatment is directed at alleviating the underlying cause. However, in most cases, there is no way to reverse cataracts. In completely vision-impaired pets, a surgical procedure to remove the lens and/or replace the lens with an artificial lens may be recommended.

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