CATARACTS

General Information:

A cataract is any abnormal opacity (cloudiness) of the lens or its outer covering (capsule). The opacity may range from a tiny spot to total loss of transparency. The lens is an M and M-shaped transparent structure that lies directly behind the iris and pupil. The cornea, aqueous humor, lens and vitreous body are elements that bend (refract) light waves to form an image upon the retina. The cornea accounts for about 80% and the lens for 20% of the light-bending action. Causes of cataracts include heredity, metabolic defects, injuries and aging. The rate of cataract development ranges from a few days to years.

Treatment Information:

The advent of phacoemulsification has increased the success rate after canine cataract surgery from 60-65% to 90-95%. In phacoemulsification surgery the lens is fragmented through a 3 mm incision with a titanium needle that vibrates at 30-50,000 cycles per second. Because the anterior chamber is not allowed to collapse, complications associated with fibrin exudation are rare. Equally importantly, phacoemulsification surgery utilizes automated irrigation-aspiration techniques to thoroughly remove lens cortical material from the peripheral lens capsule. As a result, chronic lens-induced uveitis is not nearly the problem that it is after extracapsular lens extraction.

Alternatively, lens removal (cataract surgery) in animals is still a suitable choice in some cases. Your pet must have restricted exercise for a time post-op since normal animal behavior can result in post-surgical injury, while human patients can be instructed to observe certain precautions. Some animals do not see for several weeks after surgery; others see after a few days.

In either case, most ophthalmologists routinely replace the natural lens with a prosthetic lens implant made of polymethylmethacrylate. Lens implantation after cataract surgery results in vision acuity that is nearly normal.

Some pets may not be suitable for cataract surgery due to age, health and psychological make-up. If your pet should not undergo surgery, do not be discouraged, since it will probably be an acceptable pet despite its handicap.

If you feel that surgical correction is a good choice for your pet, please consult your veterinarian, who may perform the surgery or may recommend the surgery be performed by a board certified veterinary ophthalmologist.

We hope that you will find this information helpful in your quest for better pet care. If you have any questions or comments, please feel free to e-mail us.

David E. Hammett, DVM
and the Staff of All Creatures Veterinary Clinic, PC