The lens of the eye is a living ocular tissue that is transparent when healthy. A normal lens helps to focus light on the retina, a light-sensitive nervous tissue located at the back of the eye. A cataract is an abnormality of the lens in which it opacifies, or becomes cloudy and non-transparent causing light to scatter. When a large portion of the lens becomes cataractous it prevents formed light from reaching the retina resulting in poor vision.
A cataract can assume a variety of appearances such as small spots, a cracked-ice appearance, a diffuse milky haze, a “pearl-like” sheen, or white streaks. It may initially affect a small area and progress to involve a larger portion of the lens. Rate of progression is difficult to predict, though it tends to be more rapid in younger animals. Cataracts may develop in one or both eyes at the same or different times.
Many cataracts in dogs have a hereditary basis. Cataracts can also result from injury to or inflammation within the eye or systemic diseases that affect the eyes. Diabetes mellitus is the most common disease associated with cataracts in dogs. In fact, 80% of dogs will develop cataracts within 18 months after being diagnosed with diabetes. Although it may be difficult to determine the specific cause underlying cataract formation, typically cataracts that develop in the absence of other signs of disease are assumed to be inherited. Poor nutrition is an uncommon cause of cataracts, but has been reported in some young dogs.
Ideally, the health of the retina and other parts of the eye should be evaluated prior to the
formation of complete cataracts. If the cataract involves the entire lens, the area behind the lens may not be able to be examined directly. In these cases an electroretinogram (ERG) will be necessary to determine if the retina is functioning. If the ERG shows that the retina is not working, then cataract surgery will not improve vision. Cataracts are classified by cause, area of involvement, and stage of progression. Not all cataracts lead to blindness, but cataract surgery is often recommended if a cataract is causing significant vision impairment or rapidly progressing to involve more of the lens.
Medical remedies have been inaccurately advertised as effective for the treatment of cataracts. There is no proven medical treatment known to reverse, slow, or prevent the formation of a cataract. Some promoted agents actually worsen the cataracts rather than improve the condition. Surgery is the only effective treatment both in animals and humans and often provides a return of functional vision to pets.
Once the cataract has progressed to significant vision impairment in the affected eye, cataract surgery is often recommended. If one eye has a completely formed, vision-impairing cataract and the opposing eye has a rapidly developing cataract, some veterinary ophthalmologists recommend surgery before the second cataract is complete. Surgery has been performed successfully on dogs and cats between 6 months and 18 years of age. The pet’s general health is evaluated before cataract surgery.
For more information on this subject, speak to the veterinarian who is treating your pet.
© 2011 BluePearl Veterinary Partners