There are a number of diagnostic tests that can be conducted to confirm whether a cat has cataracts and, if so, to determine the cause of the condition. A veterinarian evaluating a cat with cloudy eyes or ice-blue “chips” in its pupils will probably have a tentative diagnosis of either cataracts or nuclear sclerosis in the back of his mind. The doctor will take a thorough history from the cat’s owner, including its vaccination history, diet, indoor/outdoor activities and any recent changes in personality, behavior, appetite or activity level. It will be especially important for the owner to describe when she noticed the eye cloudiness and whether it has changed at all since that time. The veterinarian will also perform a complete physical examination, including assessing the eyes using an ophthalmoscope. The initial work-up will include evaluation of pupil size and symmetry and assessment of pupillary light reflexes. The veterinarian will check the “menace reflex” by moving one hand swiftly toward the cat’s face then stopping abruptly, assessing its reaction. Another test to detect vision deficiencies is to throw a cotton ball onto the floor while watching to see whether the cat follows the movement. The veterinarian may recommend routine blood and urine evaluation, although the results of those tests are typically unremarkable in cats whose only problem is cataracts.
There are a number of diagnostic tests that can help a veterinarian determine whether cataracts are present and, if so, why they appeared. The Schirmer tear test can be used to evaluate tear production, and the eyes can be stained with a fluorescein dye to help assess the structural integrity of the cornea. These two tests are used to evaluate the moisture level of the eye, look for possible foreign bodies and determine whether the cornea has been damaged. A tonometer can be used to identify the pressure of the fluid inside the eyes, to check for glaucoma. A slit lamp instrument can be used to examine the lens of the eye and other structures. Assuming that intraocular pressure is normal, the veterinarian may dilate the cat’s pupils with eyedrops and use a penlight or other light source to evaluate the cataract. Anesthetic drops are normally applied to the eyes before these tests, to ensure a painless examination and accurate test results. Ocular ultrasonography and electroretinography are available for advanced evaluation of the retina and other eye structures. These advanced diagnostic tests are normally performed if surgery is anticipated. Once cataracts have been diagnosed, further blood tests may be recommended to rule in or out any underlying medical conditions that may be involved.
If you notice any change in your cat’s eyes – especially cloudy areas - schedule an appointment with your veterinarian. Many feline eye disorders worsen progressively if not treated in a timely manner. Prompt diagnosis and treatment can help preserve a cat’s vision and relieve its discomfort.