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Cataracts

Twenty years ago a diagnosis of cataracts would have meant blindness in the effected eye in most cases. Some dogs that have cataract will be able to see well enough to have a decent life without surgery. Many dogs that have cataracts also have other problems that make the loss of vision more serious (aging changes like arthritis and other diseases that predisposed them to developing catartacts). Many dogs that develop cataracts will later develop other problems associated with inflammation caused indirectly by the presence of the cataract. At Foothills Animal Hospital we will suggest that, if you can afford surgery, we refer you to a veterinary opthomologist for assessment of the eye for cataract surgery. Veternary opthomologist are available in Greenville, Columbia, Athens and Charlotte. However, the surgeons that work out of Greenville actually do the surgeries for cataracts in Charlotte. Rechecks are done in Greenville.

If the cost of surgery prohibits consideration we will do our best help advise you on management of the reduction or loss of vision that will happen. Obviously, minimizing changes in the environment and understanding of your pets limitations may allow them to have a good life without surgery. On the other hand we would ideally like to have our pets enjoy the quality of life that good vision allows.

Question and answer

What are cataracts?

A cataract occurs when the lens in the eye turns opaque or white. The lens is the spherical body behind the pupil that focuses light rays. It is situated toward the front of the eye behind the cornea and iris. It normally is highly transparent. The lens can become totally or partially opaque due to the cataract. The cataract blocks the light rays, thereby impairing vision. Cataracts are common in dogs, representing one of the most important causes of vision loss. They are uncommon in cats.

What causes cataracts?

Most cataracts are inherited. Hereditary cataracts affect many dog breeds. Breeds that are affected with hereditary cataracts that typically progress to blindness are the miniature poodle, American cocker spaniel, and miniature schnauzer. Other commonly affected breeds are the golden retriever, Boston terrier, and Siberian husky.

Other causes of cataracts include:

What are the signs of cataracts?

If cataracts occupy less than 30% of the lens, or if they affect only one eye, they often go unnoticed. When cataracts occupy more than 60% of the lens, vision problems become obvious. The pet guardian probably will notice that the pet is having difficulty seeing. Vision impairment is noticed usually before any cloudiness in the eye is seen. If the cataract is caused by diabetes mellitus, the pet may have signs of diabetes, including excessive urination (polyuria), excessive thirst (polydipsia), and weight loss.

How are cataracts diagnosed?

Cataracts are diagnosed by a good medical history and a thorough eye examination. Cataracts often are mistaken for sclerosis of the lens, a normal aging process. Sclerosis of the lens does not cause vision loss, and the veterinarian can distinguish the two easily on examination of the eye. Laboratory tests, except for determination of blood sugar, usually are not necessary because most are hereditary cataracts. Routine complete blood counts and serology (the study of antigen-antibody reactions) are used to screen for infectious diseases when cataracts are associated with anterior uveitis. Ultrasound imaging of the eye may be indicated when cataracts are advanced and surgery is anticipated, or to rule out other eye defects. Electroretinography (a graphic recording of the changes in the retina after stimulation by light) should be performed to evaluate the retina before surgery to rule out retinal degeneration or other retinal diseases.

How are cataracts treated?

Animals with cataracts of all types should be monitored carefully for cataract progression. Hereditary cataracts in young dogs can progress quickly. Surgery is the treatment of choice for hereditary cataracts. Surgery may or may not be indicated to treat nonhereditary cataracts. Eye drops may be prescribed prior to surgery. Surgery normally can be done on any hereditary cataract that is causing or will cause vision loss. The prognosis for cataract surgery is better if surgery is done early in the course of cataract development. It is not advisable to delay surgery until the animal is blind in both eyes. Pets undergoing surgery may be hospitalized or may be cared for at home. Rarely is hospitalization required for longer than 48 hours.

What is the prognosis for animals with cataracts?

Once a cataract develops, its rate of progression varies depending on its location within the lens and the age of the animal. As the normal lens ages, lens protein becomes insoluble and sclerotic, conditions which inhibit cataract progression. As a result, a small cataract in a one-year-old cocker spaniel may enlarge to cause blindness within several months, whereas a cataract of the same size in a 10-year-old poodle may require years to cause blindness. Cataracts caused by diabetes mellitus usually progress rapidly. With appropriate surgery, the prognosis (outcome) for good vision is excellent after removal of hereditary or diabetic cataracts. The prognosis after removal of other types of cataracts varies with the cause of the cataract.

The following is a "blurb" from a referral clinic that is used for their cataract patients.

A cataract is a clouding of the lens inside the eye and is the most common cause of blindness in dogs. Cataracts can be caused by injuries or diabetes, but most cataracts in dogs are inherited. Any opacity, or or clouding, in the lens is called a cataract; very small spots do not significantly affect vision. However, most cataracts will progress, and ultimately cause blindness. The lens is located behind the colored iris; thus when a cataract occurs, the pupil may appear white. Vision through a mature cataract is like looking through white painted glass.

There are no medications which are effective in treating or preventing cataracts. A cataract is not a growth; treatment requires surgical removal of the lens and, once removed, a cataract cannot recur. Cataracts are not treated with lasers; the surgery to remove the lens uses phacoemulsification, the same procedure used in people. Once the lens is removed, it is replaced with an artificial lens inserted into the pocket formed by the original lens capsule which remains in the eye. Occasionally, there is a weakness in this capsule which is detected during surgery. In these cases, sutures may be used to support the artificial lens. If replacement of the lens is not possible, the cataract will still be removed, with resulting vision which is somewhat blurry but significantly better than before surgery. One or both eyes may be candidates for surgery; the doctor will discuss these options with you.

Cataract surgery is approximately 90-95% successful. However, this means that in 5-10% of cases, complications may prevent vision recovery. The purpose of the examinations before and after surgery is to detect and prevent these complications whenever possible. In uncomplicated cases, vision will begin to improve within a few days; after six weeks, healing is usually complete and medication is discontinued.

Once the doctor has examined your pet and surgery has been agreed upon, a blood analysis will be done to detect any generalized illness and thus minimize the inherent risks associated with general anesthesia. Eye drops will be dispensed to be started before the surgery. You will use these medications after the surgery as well. Your pet will be admitted to the hospital on the morning of the surgery. The hair will be clipped from the area around the eyes and the front legs (to administer the anesthetic). An electro-retinogram test may be necessary to evaluate the function of the retina.

The surgery takes approximately one hour per eye. Your pet will be monitored in the hospital for several hours after surgery. Although overnight hospitalization is not required, he will need to come back for the first re-examination the day after surgery. When your pet goes home, he will be wearing a large plastic collar to prevent him from rubbing at the eyes. Although he may not like it, he will learn to tolerate the collar and can eat and sleep with it on. It is essential to avoid injury to the eyes after this delicate surgery. Please keep your pet away from other animals during these first two weeks. No bathing or strenuous exercise. Following cataract surgery (in people as well as dogs) there is no significant discomfort, thus pain medication is not necessary. Additional re-examinations will be scheduled at intervals after the surgery and additionally as needed.

The majority of the information in this page is has been taken from VetMedCenter.com. For further information about this useful source of informtion follow the link or look, on the internet, at www.vetmedcenter.com.