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CORNEAL ULCERS

What is a corneal ulcer?

An ulcer is a break in the outer surface of tissue. A corneal ulcer is therefore a break in the outer layer of the cornea. Ulcers may occur from a variety of conditions such as scratches by other pets, foreign material such as pieces of grass, sand or dirt getting into the eye, from a lack of tear production and from a failure of the eyelids to remain completely closed during sleep. Uncomplicated ulcers, although painful, should heal in 3 to 10 days (depending on the size) when appropriate treatment is used. Those ulcers that persist are considered complicated.

What types of ulcers are there?

Corneal ulcers fail to heal for two reasons. The first category is comprised of those that fail to heal due to external causes. External causes include: ongoing trauma, unresolved infection, foreign material embedded within the eyelid or in the cornea itself, the failure of the patient to close its eyes fully during sleep, the lack of tear production and abnormally placed eyelashes. These ulcers require treatment of the external cause as well as the ulcer to allow healing to occur.

The second category is those ulcers that fail to heal for internal reasons. These are usually primary tissue healing problems or other conditions inside the eye that prevent healing. Primary tissue healing problems refer to conditions at the cellular level in which the cornea itself fails to heal in a normal fashion. This process is recognized in certain breeds, like the Boxer, and older dogs of any breed and are sometimes referred to as a ³boxer ulcer.² Another term for this type of ulcer is ³indolent ulcer.² Other ocular conditions that would prevent corneal healing would be unresolved glaucoma or inflammation within the eye.

How are ulcers diagnosed?

Evaluation of a patient with a corneal ulcer requires a number of diagnostic instruments and techniques. Probably the most important in the evaluation of a corneal ulcer is using the slit lamp-biomicroscope. This instrument permits the veterinary ophthalmologist to carefully evaluate the cornea and ocular structures with a high degree of magnification and resolution. Stains are used to determine the size of the ulcer and if the edges are undermined. Frequently, specimens are obtained for bacterial culture, virus isolation and cytological evaluation.

How are ulcers treated?

Treatment of a non-healing corneal ulcer is dependent on the results of the diagnostic procedures. Ulcers due to external causes require those causes to be treated and, normally, healing rapidly follows. Those that involve other ocular diseases will require those diseases be treated to permit healing of the ulcer. The most frustrating ulcer to treat may be the ³healing defect² ulcer. These ulcers, although generally not sight threatening, take a long time to heal. If healing is prolonged, severe scarring and possible vision loss may occur. Treatment consists of stripping the surface off the cornea and pricking the corneal surface with a needle to Œroughen¹ it. Treatment with antibiotics, medications to dilate the pupil and agents that increase the adherence of the surface to the next layer is then begun. If these therapies do not work a surgical procedure known as a superficial keratectomy is recommended.

What about severe ulcers?

If the ulcer becomes deep, a perforation of the cornea may be the result. These ulcers require aggressive surgical intervention and subsequent medical treatment. Various surgical techniques have been used to treat deep corneal ulcers. The most common procedures used in this clinic are a corneal graft or pedicle conjunctival graft. A corneal graft may be used when the ulcer is along the center of the cornea or in cases of very large, sight-threatening ulcers. The advantage of this procedure is that it provides an immediate seal to the corneal ulcer with a healthy piece of ocular tissue. The graft will scar to some degree, yet vision is possible through the graft. The second technique involves the stitching a piece of conjunctiva (the moveable white tissue of the eye) into the corneal defect. The advantage of this procedure is that it also provides an immediate seal and that it brings healing blood vessels to the area. The tissue remains in place for 4-to-6 weeks. Once healed, the graft may be trimmed after applying a local anesthetic. Corneal ulcers are a frequent problem in veterinary medicine. Your regular veterinarian is equipped to evaluate and manage most of the non-complicated problems. Only those patients with severe or chronic ocular diseases are referred for evaluation to the veterinary ophthalmologist who is specially trained and equipped to treat unusual ocular diseases in pets. Our goal is to help your pet heal and stop hurting.

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