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During an ophthalmic (eye) exam, a veterinarian may perform a number of tests. These tests can help identify (1) problems with the eyes or (2) underlying diseases that may affect the eyes. Your veterinarian may conduct the exam or recommend that a veterinary ophthalmologist (an eye-care specialist) evaluate your pet.
Why Should Pets Receive an Ophthalmic Exam?
Your pet’s eyes should be examined as part of a regular physical exam. However, more thorough testing is needed in the following circumstances:
An ophthalmic exam may include many different tests. While a complete description is beyond the scope of this article, the most common tests are outlined here. Your veterinarian may choose to conduct some or all of these tests, depending on the nature of your pet’s problem.
The ophthalmic exam often begins with an evaluation of the pet’s vision. The veterinarian may observe how the pet moves around the room or if he or she follows a cotton ball when tossed near the eyes. A menace test may also be conducted to see if the pet blinks when a finger is moved toward, but without touching, the eye.
A pupillary light reflex test is used to evaluate the retina (the sensory membrane that lines the eye), the muscles controlling the iris (the colored portion of the eye), the nerves, and the part of brain that controls visualization. The veterinarian will shine a bright light into each eye and evaluate both eyes for pupil constriction.
If the veterinarian is concerned about tear production, he or she may perform a Schirmer tear test. A small strip of paper is positioned in each lower eyelid and held in place for 60 seconds. This test can help determine if your pet is producing enough tears to lubricate the eye properly.
An ophthalmic exam usually includes a thorough evaluation of the outer eye structures, including the tissues around the eyes, the eyelids, the duct where the tears drain from the eyes, and the cranial nerves that affect the eyes. At the same time, the veterinarian will check the eye for inflammation and infection as well as for foreign bodies and unusual growths. The lens of the eye will also be examined for signs of cataracts.
It is common for pets to inadvertently scratch the cornea (the clear layer on the front of the eye). Because these painful abrasions or ulcers are not always visible with the naked eye, your veterinarian may conduct a fluorescein stain test. When a small amount of lime-green dye is placed in the eye, any defect in the cornea will take up the dye, displaying the location and size of the abrasion.
Another painful condition for pets is glaucoma (high eye pressure caused by improper fluid drainage within the eye). Certain breeds and some diseases, such as diabetes, are associated with glaucoma.
Before testing eye pressures, the veterinarian will first place a few drops on the eye to numb the eye surface. Most likely, the veterinarian will use an instrument that looks like a pen to gently tap the eye surface. This instrument provides a reading of eye pressure. High pressure is a sign of glaucoma, while low pressure may be a sign of uveitis (inflammation of an interior layer of the eye).
An ophthalmic exam also includes a thorough inspection of the fundus (the back of the eye). A few drops will be placed into your pet’s eyes to dilate (enlarge) the pupils. It may take 15 to 30 minutes for the drops to work. The veterinarian will use a special instrument to examine the interior of the eye, including the retina, the blood vessels, and the optic nerve.
If you notice any abnormality in your pet’s eyes or vision, contact your veterinarian immediately. Many eye conditions are extremely painful or could result in the loss of vision, if not attended to promptly. An ophthalmic test will help identify the source of the problem so that your pet receives proper treatment and pain relief as soon as possible.
This article has been reviewed by a Veterinarian.
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