Defining Cataracts in Cats
A cataract is defined as any opacity of the lens that impairs the eye’s ability to absorb and transmit light to the retina. This therefore interferes with a cat’s vision. Any spot on the lens of a cat’s eye that blocks light technically is a cataract, regardless of its size. Cats of either gender can develop cataracts, although they are much less common in cats than in dogs. Cataracts are seen more frequently in older cats, but sometimes they are present at birth or develop early in life. Regardless of their cause, the symptoms of cataracts are the same. Affected cats have cloudy pupils which may have what look like icy-blue “chips.” They have impaired vision in affected eyes, ranging from mild to blindness. Cataracts can have a strong genetic component. Other contributing causes include nutritional deficiencies, low calcium levels, exposure to toxins, radiation, electric shock and blunt or penetrating trauma.
Causes of Feline Cataracts
Causes of Cataracts in Cats
Cataracts in cats and other animals can be caused by a number of different things. Many feline cataracts are congenital, which means that they are present when the kittens are born. Cataracts also often develop as a natural result of the aging process. Some cats get cataracts from poor nutrition or traumatic eye injuries. Nutritional deficiencies are one of the most common causes of feline cataracts. Taurine is one of the dietary nutrients that is essential to the health and normal development of feline eyes. Cats that are fed a sub-standard diet that lacks adequate sources of taurine, including a nutritionally unbalanced homemade diet, have a heightened risk of developing cataracts, usually in both of their eyes. Inflammation from physical trauma or underlying systemic medical conditions can also contribute to cataracts. Injuries to one or both of a cat’s eyes as a result of scratches received during a cat fight frequently contribute to non-congenital cataracts in cats. There seems to be a strong familial or genetic component to the development of cataracts. Other things that can contribute to feline cataracts include low circulating blood calcium levels, exposure to toxins or poisons, radiation, electrical shock and blunt or penetrating trauma. Unlike dogs, cats usually don’t develop cataracts as a result of diabetes.
At the most basic physiological level, cataracts occur when there is some change in the composition or arrangement of protein molecules and fibers in the lens of the affected eye. Fortunately, cataracts aren’t particularly common in companion cats. However, they have been diagnosed more and more frequently in recent years. This probably is due in part to the fact that cats are living longer these days as a result of ongoing improvements in nutrition and health care. Cataracts tend to become more pronounced as a cat ages, although this isn’t always the case. Cataracts can be painful, especially if they worsen over time. In severe cases, progressive cataracts can eventually lead to complete blindness.
Preventing Cataracts in Cats
Because congenital cataracts are thought to be strongly influenced by genetics, one of the most important ways to reduce their prevalence in cats is to remove affected animals from the breeding population. This won’t guarantee that future generations will be free from this potentially devastating condition, but it will help to reduce the number of cats with hereditary cataracts. Fortunately, while cataracts almost universally have some adverse impact on a cat’s vision, they don’t affect its overall health. Cats seem to adjust extremely well to progressive vision deficiencies, even without treatment. Nonetheless, surgical removal of feline cataracts is highly successful. The prognosis for cats with cataracts is usually excellent, if their condition is identified and treated early in its course.
Symptoms of Feline Cataracts
Effects of Cataracts – From the Cat’s Point of View
The term “cataract” refers to any opacity or cloudiness of the lens of the eye, regardless of its size. Cats of either gender can develop cataracts for a number of different reasons, although in cats most reported cases have been congenital. The symptoms of feline cataracts are the same, regardless of their cause. Some cats with cataracts act completely normal and don’t seem to suffer any adverse consequences or show any signs of decreased vision, especially if only one eye is affected. In advanced cases, most cats do experience vision deficits, which can progress to actual blindness. Sometimes cataracts are irritating and can even become painful.
Symptoms of Cataracts in Cats – What the Owner Sees
The main visible sign of a cataract is an icy blue spot or cloudiness that develops on the lens in the pupil of the cat’s eye. The cloudy spot may start and stay small or get bigger gradually over time. Sometimes, cataracts spread quickly to cover most or all of the pupil. The chief complaints by owners of cat with cataracts are that they notice cloudy spots in their pet’s eyes and changes in its vision. Cataracts can develop in one eye or in both. Many cats have cataracts from the time they are born. Abnormalities that are present at birth are called “congenital” disorders. Depending on the severity of the cataracts, affected cats can display a variety of vision problems, ranging from mild impairment to total blindness. Owners of cats with cataracts may notice one or more of the following signs that are associated with impaired vision:
- Cloudy spots in the pupil of one or both eyes; may look like an ice-blue chip
- Unusual high-stepping walk; abnormal ambulation
- Unsure footing
- Tripping over or bumping into familiar objects (walls, furniture)
- Misjudging distances
- Not recognizing familiar people
- Watery eyes
- Changes in eye color
- Changes in pupil size or shape
Cats at Increased Risk
Certain breeds are predisposed to developing cataracts, including Persians, Birmans, Himalayans and Domestic Shorthairs. This is undoubtedly due to hereditary factors. Cats can develop a condition called nuclear sclerosis, which also causes a cloudy bluish haze on the lens. It is caused by normal aging of the eyes as cats get older; the lenses lose their ability to retain water and fibers build up on the lens’ surfaces. Owners may confuse this condition with cataracts. However, nuclear sclerosis normally does not impair a cat’s vision and doesn’t require treatment.
Diagnosing Feline Cataracts
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.
Treatment Of Feline Cataracts
Goals of Treating Cataracts in Cats
The goals of treating cataracts are to restore a cat’s vision, prevent the development of secondary problems such as uveitis, glaucoma and retinal detachment and improve the cat’s overall quality of life. Owners should seek veterinary advice if they suspect that their cat has cataracts. The only way to eliminate cataracts is to remove them surgically. Short of blindness, cataracts can develop into glaucoma and retinal detachment, at which point surgery may no longer be a viable option. Some owners decide not to treat cataracts, because cats typically adjust quite well to progressive vision impairment.
Cataracts in very young kittens sometimes spontaneously improve (or never worsen) and may not need to be treated. New cataracts that have very low opacity (classified as immature, incipient, non-progressive or incomplete cataracts) may also not need treatment unless and until they interfere with the cat’s vision. In some of these cases, topical anti-inflammatory eye drops may increase the cat’s comfort. The progression of cataracts caused by nutritional deficiencies may be delayed with appropriate dietary supplementation under a veterinarian’s supervision.
The only effective treatment for cats whose vision is impaired from cataracts is surgical removal of the affected lens (cataract extraction) and replacement of it with an artificial lens. Before surgery, the cat’s eyes should be examined with ophthalmic ultrasound and electroretinography, to make sure that the back part of the eyes are normal. There are several different ways to extract cataracts, each of which normally is performed by a specialized veterinary eye doctor (ophthalmologist). These procedures include: 1) extracapsular lens extraction (ECLE); 2) intracapsular lens extraction (ICLE); and 3) phacofragmentation or phacoemulsification (“phaco”). Most ophthalmologists prefer the phacofragmentation technique, which uses ultrasound waves to liquefy the damaged lens. The liquefied particles are removed through a sensitive suction instrument, and the eye is irrigated with a soothing sterile solution. An artificial lens can be implanted into the eye to restore vision; otherwise, the cat will be extremely far-sighted, with little useful vision. The prognosis is best if surgery is done early in the course of cataract development. Of course, the veterinarian will make sure that the cat is healthy and systemically stable before any surgery takes place.
Cataract surgery is expensive, and many owners decide that it is unnecessary due to their cat’s ability to acclimate to their environment even with vision loss. Cats use their sense of smell for most of their navigation activities and actually usually don’t have very good eye-sight to begin with. Cats with decreased or total loss of vision should be kept indoors at all times for their safety and well-being. If an owner elects not to have his cat’s cataracts removed, they still should be monitored by a veterinarian regularly to keep track of their progression. If a cat loses all or most of its vision, it often will have some accompanying pain. At that point, it may be best to surgically remove the affected eye(s).