The complaint “Doctor, Fluffy’s eye is white all of a sudden ” is common by pet owners.

It actually may be one of several different conditions, requiring different treatments, or in some cases no treatment at all.

One of the most common causes for an eye to appear white in the center is a normal aging change called nuclear sclerosis, also known as lenticular sclerosis. This is a slow, progressive cloudiness that develops in the center of the lens as an animal gets older.

Even though this is a condition that takes years to develop, pet owners sometimes don’t notice it until it has become fairly advanced. The outer rim of the lens usually remains clear, but may only be visible when the pupils are dilated.

Nuclear sclerosis causes a gradual loss of detail vision, and in advanced cases the pet may only be able to distinguish large shapes and areas of light and dark. There is no treatment for nuclear sclerosis. Owners sometimes think that a pet has cataracts when they have nuclear sclerosis.

A cataract is a change in the crystalline structure of the lens that causes it to become white. It usually takes years to develop but may appear suddenly in a matter of weeks in some cases.

Cataracts occur in various forms and may involve part or all of the lens. The lens loses its natural elasticity and becomes hard. The pet can only distinguish light and dark in an eye if the entire lens is affected. Several complications to cataracts may occur, including luxation (detachment of the lens from the fibers that hold it in place), glaucoma (a painful increase in the pressure inside the eye) or endophthalmitis (a severe inflammatory condition inside the eye).

Cataractous lenses can be removed and replaced with a lens implant, just as in humans. This can prevent possible serious complications from leaving the lens there and restore normal vision to many pets that would otherwise be essentially blind.

There are also problems that may occur with the cornea that may make the eye appear white. The cornea is the clear “dome” over the front of the eye. There is a delicate layer of cells on the outside and inside of the cornea that keeps it from absorbing too much fluid. Any break in these linings can cause the cornea to swell and lose its normal transparency.

Damage to the outside epithelium in the form of a scratch or ulcer usually causes a part of the cornea to become hazy or white. Chemical irritation, such as from getting shampoo or flea spray into the eye, may make the entire cornea opaque. Different treatments may be required.

Damage to the endothelium on the inside of the cornea may occur from changes in pressure inside the eye or systemic diseases that affect the eye. Treatment of these conditions frequently involves oral medication in addition to topical application of drops or ointments.

If your pet’s eye looks abnormal, or if your pet shows discomfort by squinting or rubbing its eye, have your pet’s doctor examine it and start you on the proper course of treatment.

— Dr. Greg McGrath is a veterinarian at Cedar Lake Pet Hospital in Biloxi, Miss.