Cats and dogs both have a nictitating membrane (also called a third eyelid) in each eye. The third eyelid normally functions to provide physical protection to the cornea and to produce a significant portion of moisturizing tear film to keep the eyes well-lubricated. Cherry eye is the most common disorder of the feline third eyelid. It is especially prevalent in certain breeds, such as the Burmese and Persian. Fortunately, this condition is not particularly common in cats, nor is it difficult to diagnose. Owners who notice a doughy red mass of tissue that suddenly pops out from the inner corner of one or both of their cat’s eyes should take their pet to a veterinarian as soon as possible. Cherry eye isn’t a medical emergency, but it still is important to treat the condition promptly to prevent permanent ocular damage. The initial discovery and evaluation of cherry eye is almost always first made by the cat’s owner.
Cherry eye is usually diagnosed based simply on the veterinarian’s physical examination of the animal, because it is so obvious and virtually impossible to ignore. In young cats, no special tests are needed to confirm that the gland of the third eyelid has prolapsed or everted, especially if the condition came on suddenly, which almost always is the case. Older cats that gradually develop fleshy red masses in or around one or both of their eyes are more likely to be suffering from some form of cancer. In those cases, the veterinarian probably will recommend taking a biopsy of the mass and submitting the sample to a pathology laboratory, to determine exactly what it is. Sometimes, the veterinarian will take an excisional biopsy, which involves removing the entire mass rather than removing only a small slice of it. A less invasive diagnostic tool is taking a sample using a fine needle aspirate (FNA). This technique involves piercing the lump with a sterile needle attached to a syringe and pulling back on the plunger to extract cells and fluid. The contents of the syringe are then expressed onto a glass slide and examined under a microscope.
Any abnormal eye condition merits a thorough ophthalmic examination. This involves assessing the cat’s pupillary light reflexes, evaluating the size of its eyeballs, retropulsing the eyeballs and evaluating intraocular pressure (the pressure inside the eyeballs). The cat’s demeanor, hydration status and overall body and coat condition will be evaluated as part of the physical examination. Advanced diagnostic techniques, including ultrasound, computed tomography (CT) scan and magnetic resonance imaging (MRI), are available at specialized referral centers and veterinary teaching hospitals but aren’t often used to diagnose eye problems.
Fortunately, diagnosing cherry eye is simple. Surgical correction of the condition is also fairly simple and usually is quite successful.