Cataracts occur when the normally transparent lens of the eye opacifies or becomes cloudy. The lens is deep within the eyeball, as depicted by the darker gray area in the image below right. Even though the cloudiness may look like it is on the surface of the eye (the cornea), it is not. Any spot on the lens that is opaque, regardless of size, is a cataract. Cataracts may affect one or both eyes. Some cataracts are clearly visible to the naked eye, appearing as white or bluish dots, while others are visible only by examination with an ophthalmoscope.

Cairn Terrier with bilateral cataracts	Anatomy of the dog's eye

Many dogs develop cataracts as they age. The cataracts may stay small or may worsen until the dog becomes blind. The majority of cataracts are inherited and are found in breeds such as the Cocker Spaniel, Poodle, Husky, Schnauzer, Golden and Labrador Retrievers, and terriers. Diabetes, trauma, inflammation, and puppy milk replacers can also cause cataracts.

A common occurrence in developing cataracts is development of an allergic type of reaction to the cataract. This allergic reaction can result in many complications such as scar formation and glaucoma which in themselves may cause blindness.

In diabetic dogs with cataracts, there is frequently a spontaneous lens capsule rupture which can cause other complications. Within 4 months of cataract formation, your diabetic dog should receive a full eye exam and removal of the cataracts should be considered. Early surgical intervention, prior to secondary complications of glaucoma and loss of retinal function, is associated with a favorable outcome.

If your dog develops cataracts, please see your veterinarian so that their progress may be monitored and your dog can be checked for complications. You may need a reference to a veterinary ophthalmologist. If you wait to have your dog's eyes evaluated until the cataracts are extremely opaque, your veterinary ophthalmologist. may have to perform more complicated tests on your dog to determine the extent and cause of the loss of sight.

Treatment of Cataracts

Surgery

Cataracts may be surgically removed in one or both eyes. Your veterinary ophthalmologist will perform a full eye exam and then may also perform two additional special tests to check the health of the retina or nerve layer in the back of the eye. These tests, the ERG (electroretinogram) and ultrasound, are not painful but sedation may be given so that your dog does not move his head or eyes. The tests have virtually no risk associated with them. If your pet does not pass these tests, removal of the cataracts would not improve vision; therefore, surgery should not be performed.

Cataract surgery is elective although recent scientific evidence recommends early surgery in the diabetic dog. The surgery is expensive, usually US $1000-1500 per eye. It also requires a significant time commitment on the part of the owner. Eye drops must be administered several times daily before surgery and for about 6 weeks after surgery. Your dog must wear a protective plastic e-collar for 2 weeks after surgery, and your pet will not be able to be groomed or vaccinated during the 6 week healing period. The postoperative checkups are usually performed the day after surgery and also one, three, and six weeks after surgery. At that time, medications may be gradually discontinued and long term checkups are made about 4 months after surgery and then once a year. The success rate is OVER 90%. As with any surgery there are risks and your veterinary ophthalmologist will discuss theses risks with you.

The surgery is performed under general anesthesia and depending on the specifics of the cataracts, age, and cause the ophthalmologist may perform either a small incision technique (phacoemulsification) or a large incision method (extracapsular cataract extraction). The small incision technique is more common today and carries the benefits of shorter surgery and healing times. Phacoemulsification is the same technique performed for human cataract removal; a tiny probe breaks up the cataract with ultrasonic vibration and then removes the cataract particles. Lasers are not used. After removal of the cataract(s) your ophthalmologist may suggest replacement of the lens with an artificial lens to obtain sharper vision, just like in human cataract surgery.

Download a cataract brochure (.pdf) from the American College of Veterinary Ophthalmologists by clicking here.

Eye Drops

A number of non-prescription eye drop formulations are marketed that claim to reduce cataract formation or to "dissolve" existing cataracts. None of these eye drops have been tested in controlled clinical trials but rather rely on subjective reports of improvement by the dog owners. These products are not recommended until they have been thoroughly evaluated.

A 2006 veterinary study authored by DL Williams DVM evaluated a prescription formula, Ocluvet™, a topical nutritional antioxidant formulation including N-acetyl carnosine. Although 80% of dog owners using the drops reported improvement, a number of scientific tests were employed to objectively measure the results of the drops also. Dr. Williams reports, "The study demonstrates some marginal reduction in lens opacification in a substantial number of cases of canine cataract with the use of a topical nutritional antioxidant formulation including N-acetyl carnosine. Lens opacification was improved with treatment in eyes with immature cataract or nuclear sclerosis while in eyes with mature cataract or cataract with associated intraocular inflammatory pathology less reduction was seen."

The results obtained with Ocluvet™ were measurable but quite small. The best results were obtained when dogs with very early cataract formation were treated.

The Bottom Line

All older dogs are at risk for developing cataracts. Some breeds are more susceptible. Diabetes definitely increases the risk of developing cataracts and is also associated with other eye complications.

As soon as your dog is diagnosed with cataracts, ask your vet about the possibility of using prescription eye drops such as Ocluvet™. Don't waste your money on non-prescription, unproven drops. These drops work best in early stages of cataract formation. Your dog will still need to be monitored by your general veterinarian. In addition, within 4 months of being diagnosed with cataracts, an evaluation by a veterinary ophthalmologist is recommended.

References:

American College of Veterinary Ophthalmologists: Cataracts. http://www.acvo.org/

Kerry Kettring DVM, Dipl ACVO. A Cure for Cataracts? All Animal Eye Clinic.

Wilkie DA, Gemensky-Metzler AJ, Colitz CM, Bras ID, Kuonen VJ, Norris KN, Basham CR. Canine cataracts, diabetes mellitus and spontaneous lens capsule rupture: a retrospective study of 18 dogs. Vet Ophthalmol. 2006 Sep-Oct;9(5):328-34.

Williams DL, Munday P. The effect of a topical antioxidant formulation including N-acetyl carnosine on canine cataract: a preliminary study. Vet Ophthalmol. 2006 Sep-Oct;9(5):311-36.