You may notice your cat becoming hesitant about moving around the house. Or, you rearranged the furniture and your cat is bumping into things. What’s happening? Your cat may be going or have become blind.
Blindness in cats has numerous causes. Rarely, a cat may be born blind or have serious neonatal eye infections that cause blindness. Although cats that are blind from birth can lead relatively normal lives, they should not be allowed outside. These cats tend to use their senses of hearing and smell for guidance and can compensate fairly well if they are in a familiar environment like their home.
Trauma, along with some other conditions such as retinal detachment, can lead to acute blindness. A cat who has had normal vision and becomes acutely blind does not have time to adjust to gradual vision loss. These cats may either freeze in place due to fear or run wildly in a panic. It is best to confine these cats to a large dog crate with litter box, food and water bowls, and a bed to curl up in while seeking veterinary consultation. A veterinary consult should be sought in any case of acute blindness.
Eric C. Ledbetter, DVM, DACVO, Associate Professor of Ophthalmology at Cornell University College of Veterinary Medicine, says, “The most common causes of blindness in cats are hypertensive retinopathy, glaucoma, and uveitis.” While these conditions can lead to permanent vision loss, if caught early, treatment may prevent or delay the progression to blindness.
Hypertensive retinitis results from hypertension causing retinal detachment and bleeding in the back of the eye. What causes the hypertension or high blood pressure? The most common cause of hypertension is kidney failure, although hyperthyroidism also is a culprit for some cats. Kidney failure is a common condition in senior cats that can be diagnosed (along with associated hypertension) by your veterinarian through measures of blood pressure and blood tests to evaluate kidney status. (See “Kidney Failure Is a Progressive Disease,” at catwatchnewsletter.com.)
Early diagnosis and treatment of kidney disease can slow the progression of its sequelae (including hypertension) and potentially save your cat’s eyesight. Amlodipine, a drug used to treat hypertension, may allow for some healing of a detached retina, thereby preserving or restoring some vision.
Glaucoma and Uveitis
Glaucoma is an increased pressure within the eye that can occur secondary to abnormal drainage of intraocular fluid. It will eventually put pressure on the optic nerve. If this pressure persists, permanent damage can be done to the nerve and vision loss or blindness in that eye may result.
There are two types of glaucoma. Primary glaucoma is an inherited condition and usually will affect both eyes. Cat breeds with a predisposition to this type of glaucoma include Burmese and Siamese cats.
Secondary glaucoma has an inciting cause that can vary. While both eyes may be affected, sometimes just one eye is involved. A common cause of secondary glaucoma is the third most common cause of blindness overall—uveitis.
Uveitis is inflammation of the uvea, the pigmented area between the sclera and the cornea that contains the iris, choroid, and ciliary body. Uveitis causes a buildup of proteins and inflammatory cells that block the fluid drainage ducts, putting pressure on the optic nerve and leading to glaucoma. Many viral illnesses—including feline immunodeficiency virus (FIV), feline leukemia virus (FELV), and feline infectious peritonitis (FIP)—can cause uveitis.
Glaucoma usually begins subtly. If only one eye is affected, it may be noticeably cloudier than the other eye or appear to be enlarged and/or red. The pupil will eventually dilate. You might notice your cat squinting and acting like the eye is painful.
Glaucoma can be diagnosed during a regular physical examination. Your veterinarian will use a tonometer—a tool that measures intraocular pressure—to check your cat’s eyes. Normal intraocular pressure for cats varies with the time of day, the age of the cat, and whether the cat is spayed, neutered, or intact. If only one eye appears to be affected, your veterinarian will compare the eyes. In general, intraocular pressures of 10 to 25 mmHg are considered normal, but your veterinarian also will examine the retina and optic nerve.
Glaucoma is not curable (yet). However, if it’s diagnosed early, it can be controlled, and the progression of the disease can be slowed or halted. Treatment requires the use of eye drops, which are usually well tolerated by cats. Coupling the daily treatment with a special food treat can make your cat more compliant. Cats tend not to be as painful as dogs with glaucoma, but if your cat is painful and the glaucoma has progressed enough to cause blindness, removal of the eye can provide relief in some cases.
Cataracts can occur in cats, but Dr. Ledbetter notes that they are much less common in our feline companions than in dogs. A cataract involves cloudiness or opacity in the lens of the eye that blocks light transmission back to the retina and optic nerve.
Cataracts may appear in one or both eyes and may not totally occlude vision. Cataracts can be secondary to diabetes, hypertension, exposure to toxic substances, or trauma (such as being hit by a car). If only one eye is involved, your cat will still have useful vision. If both eyes have cataracts and the retina and optic nerve are healthy, surgery may be considered to remove the affected lens in at least one eye. This surgery is done more commonly in dogs than cats and should be done by a veterinary ophthalmologist.
While many blind cats continue to lead happy lives if the cause is caught early, some of the conditions that lead to blindness can be treated to stop or slow the progression of vision loss. This is yet another reason why an annual physical examination for cats under 10 years of age is important to your cat’s health. For cats 10 years of age or older, once every six months is recommended.
Included in the annual exam will be a check of the cat’s eyes, as well as for any other conditions that could eventually cause your cat to lose her sight.
AndrewLozovyi | Deposit Photos
Helping Your Blind Cat
No matter what caused vision loss in your cat, you can make life a bit easier for her by trying to integrate these steps into your daily routine:
-Minimize furniture rearranging and clutter.
-Keep important things (food and water bowls, litter boxes) in consistent places.
-Choose toys that involve noise and smell. Food puzzles are great, and toys that jingle or crinkle can be fun for your cat. Catnip toys can attract a blind cat.
-Consider small bells on the collars of your other pets so your cat is alerted when they approach. Use extra caution when introducing any new pets.
-Block off dangerous areas, such as stairs and balconies.
-Do not allow her outside unsupervised.
-Consider different floorings to help her navigate.
-Alert your cat before touching her. Talk, hum, whistle, or clap to let her know you are about to touch her.
-Provide identification (microchip, tags) in case she gets outside alone.