Eye cancer symptoms in dogs depend on the type and location of the tumor. Often, symptoms of the most serious types of cancer appear suddenly, while less malevolent types occur gradually. Not all canine eye tumors affect vision, at least not initially. When your dog gazes into your eyes -- which he probably does frequently -- take the opportunity to not just adore him back but to check out his eyes' appearance for any abnormalities.
Tumors affecting the eyeball, called orbital tumors, usually cause eyeball protrusion. The eyelid, conjunctiva and cornea generally swell. This swelling and protrusion means the affected eye can no longer move in conjunction with the unaffected eye. Your vet cannot move the eyeball back into place because of the tumor. Fortunately, orbital tumors are usually not painful, at least when symptoms first appear.
The most common eye tumors are anterior uveal melanocytomas, which are benign. When malignant, they are usually just referred to as melanomas. These tumors are black, with the primary symptom consisting of a mass in the eye and irregularities in the pupil. The iris, or colored part of the eye, becomes chronically inflamed. The white of the eye -- or sclera -- appears red from ruptured blood vessels. This condition is painful, made more so if the dog also suffers from glaucoma, which often accompanies eye melanoma.
Other parts of the canine eye sometimes affected with melanoma include the conjunctiva, as well as the area between the sclera and the cornea. The latter are known as limbal tumors, which are often benign.
Diagnosing Eye Tumors
Your vet will perform various eye tests on your dog, including pressure testing for glaucoma. An ophthalmic exam reveals the basic location and size of the tumor. She'll take blood and urine samples, the testing of which not only reveal the general state of your dog's health but potentially whether a tumor has metastasized, or spread. For melanomas, she may take tissue samples for biopsy. Your vet also determines tumor type and whether it has spread via X-rays and ultrasounds. If the tumor is benign, she may opt to simply have your dog come in for an examination every few months for monitoring.
Treatment and Prognosis
For any malignant tumor, enucleation, or eye removal, is generally necessary. Most dogs learn to function quite well with just one eye. The prognosis depends on the type of tumor. Orbital tumors often don't have a good prognosis, because by the time symptoms appear, the cancer has already spread. Your vet may remove a substantial amount of bone around the orbital cavity to decrease the odds of recurrence. While a conjunctival melanoma usually requires enucleation, the surgeon can remove a limbal tumor without taking out the eye.