Immature cataracts rarely cause problem

Dear Dr. Thompson: During my 9-year-old poodle's last check-up, my veterinarian mentioned that he had cataracts. She reassured me that the cataracts were not causing any problems and we should be watching them as he ages, but I am wondering if there is something else that could be done?

The term cataract applies to changes in the lens of the eye. A dog's lens does not differ significantly from a human's and serves to focus light on the retina in the back of the eye. Cataracts can be on the front, back, or throughout the lens and they are classified by how much they interfere with vision and the degree to which the lens is affected.

Sometimes hardening of the lens associated with aging will make the lens appear cloudy, but is not associated with any of the major issues linked to cataracts. An older dog can become relatively farsighted as a result, which might slow him down doing the crosswords but not much else.

Cataracts can be congenital, meaning your dog was born with them, or develop with age. Ultraviolet radiation can damage the lens, and if you lived in a part of the world where the sun shines prior to moving to northwest Ohio, that might play a role. The bigger concern is if the cataracts develop as a result of an underlying disease such as diabetes. There would be other symptoms accompanying the changes in the eye such as increased thirst and urinations, which does not sound like the case with your dog.

I assume the cataracts your dog was diagnosed with are smaller and not posing a significant risk or your veterinarian would have been more proactive. Smaller, or immature cataracts tend to have a minimal impact on vision and will rarely cause problems.

However, if the cataracts progress and the covering of the lens, called the capsule, begins to leak more serious issues can arise. The contents of the lens are irritating and foreign to the body and an inflammatory reaction will develop. This inflammation can eventually interfere with the drainage of the fluid inside the eye. Over time the pressure inside the eye will build, which is glaucoma.

For dogs with more mature cataracts I recommend having eye pressures checked on regularly as a screening tool to see if glaucoma is developing. When inflammation is occurring secondary to the leaking lens, a topical anti-inflammatory may be prescribed as a preventive measure.

Fortunately, most dogs diagnosed with cataracts do not develop any problems, but your veterinarian is right that it bears some watching. Good luck.

Questions for Dr. Gary Thompson can be emailed to askthevet@theblade.com or mailed to The Blade, Attn. Ask the Vet, 541 North Superior St., Toledo, OH 43660. Dr. Thompson regrets that he cannot answer individual letters.