Understanding Cataracts

12.cataracts-300x218A cataract is an area of opacity within the lens or the lens capsule of the eye.  The eye’s lens is a soft tissue equivalent of a glass lens inside a camera.  Its purpose is to focus light into a discernable image onto the retina in the back of the eye.  Like a dirty camera lens, a cataract obstructs some of the light, making the image cloudy and darker.  Cataracts can cover all or part of the lens, reducing vision to a greater degree as the opacity is more generalized.  They can be progressive, meaning that blindness increases as the cataract matures.

There are several causes of cataracts.  Juvenile cataracts (occurring in young animals) are congenital or caused by trauma to the eye.  Almost all dogs with Diabetes Mellitus will develop cataracts even when receiving insulin therapy.  The normal aging process causes a graying and hardening of the lens (nuclear or lenticular sclerosis) which is not a cataract and does not affect vision significantly. Many older pets will have an inherited cause for cataracts that begin to develop as the animal ages.  These may progress slowly over years, or rapidly over months.  Very rapid onset of cataracts causes suspicion that an underlying disease is responsible and should be investigated.

Specifically, cataracts are abnormal deposits of opaque proteins within the lens.  There is currently no known medication or treatment to reverse the formation of a cataract.  Surgery to remove the clouded lens is the only method of restoring vision to an affected eye.  A tiny incision is made through the capsule that contains the lens.  A technique called phacoemulsification is used to ultrasonically dissolve the lens and remove it by aspiration through a needle.  Afterward, an artificial lens may or may not be implanted in the capsule.  If not, the pet will lose the ability to focus, but light is allowed to reach the retina where the brain perceives an image.  Blurry vision is easier for the animal to compensate for than complete blindness.  An artificial lens will focus the image to some degree; however, it is impossible to implant an exactly matched lens to restore 20/20 vision.  In either case, the animal’s ability to see will greatly improve after surgery.

In the past, it was recommended to wait for a cataract to fully mature before surgery.  Advancements have caused Ophthalmologists to rethink this approach, so be sure to consult a specialist about the best time to pursue cataract surgery for your pet.  Complications from surgery can include uveitis (inflammation in the eye), infection, bleeding in the eye, secondary glaucoma, and retinal detachment leading to permanent blindness.  Also, not all pets are good candidates for cataract surgery.  A complete evaluation of the eye must be performed to determine whether surgery will be of benefit to the patient.  Overall, 90 to 95% of pets who undergo cataract surgery have improved vision.

Untreated progressive cataracts will over time lead to blindness.  A mature cataract and the affected lens can eventually detach from the suspensory tissues and settle to the bottom of the eye.  It may occlude normal fluid drainage and result in glaucoma.  Glaucoma is a very painful swelling of the globe caused by increased fluid pressure inside the eye.  Cataracts may or may not cause significant problems during the lifetime of the pet.  Only your veterinarian with an Ophthalmologist’s consult can help to predict the quality of life your pet will have with a cataract.