The lens of a dog's eye is normally clear. Opacity of the lens, affecting part or all of the eye, is called a cataract. They can be inherited -- the most common cause of cataracts in dogs -- or result from trauma, diabetes or aging. Cataracts cannot be reversed and sometimes lead to blindness.
With a cataract, the dog cannot see through the affected area, so if the whole lens is covered, the eye (or eyes, if both are affected), will be blind. If a cataract blocks the eye's natural fluid drainage -- by absorbing fluid and swelling up or if it comes loose in the dog's eye and settles over the drainage area -- it can cause glaucoma. With glaucoma, fluid pressure builds up and damage to the eye can result in blindness. Over time, some cataracts dissolve, resulting in inflammation, which again can lead to glaucoma and blindness.
If both eyes are affected, cataracts are usually treated by removing the lenses, using surgery for an older dog with compact lenses, but a younger dog's soft lenses can be broken up by sound waves and sucked out -- a process called phacoemulsification. Cataracts can be left untreated if there isn't any inflammation or glaucoma and some dogs cope well without sight. Always consult a veterinarian for any problems with a dog's eyes.
- Caring For Your Dog; Dr. Bruce Fogle
- VeterinaryPartners.com: Cataracts
- Apple Tree House/Lifesize/Getty Images