The lens is transparent crystalline structure encased in a capsule which sits behind the pupil and iris, the coloured part of the eye. The role of the lens role is to focus light onto the retina.
It is predominantly made up of water and proteins with layers like an onion. A cataract is a clouding/opacity of the lens in the eye due to the proteins clumping together. This reduces the amount of light which reaches the retina causing blurred vision and eventually leads to blindness.
Cataracts occur for a range of reasons, including the natural aging process, trauma, inflammation, anterior uveitis, hypertension, metabolic disorders (such as diabetes, hypocalcemia, and hypoparathyroidism), poor nutrition and drugs (antibiotics and steroids) or toxins.
Either part of, or the entire lens can be affected, they can be unilateral (one eye), or bilateral (both eyes). Obviously, the larger the area affected, the greater the effect on your cat’s vision.
Cataracts are classified according to your cat’s age and the size of the cataract. While extremely rare, cataracts can be present at birth (congenital) or occur in young cats. When they are found in young to middle-aged cats they are known as juvenile cataracts and senile cataracts in older cats. Cataracts can progress, over months or years or quickly, over days, depending on the cause.
Cataracts are classified as:
Very small – Incipient (immature) cataract.
Small – Immature cataract.
Large (filling the entire lens) – Senior cataract.
Another condition known as nuclear sclerosis also resembles cataracts and your veterinarian will need to distinguish this from the cataract. Nuclear sclerosis occurs as the lens loses water due to aging, resulting in the formation of a blue haze. This does not impede vision and requires no treatment.
The most common symptoms is a blue/grey cloudy appearance in the pupil(s) of the eye.
Affected cats may bump into furniture or be more reluctant to explore as their vision declines.
Other symptoms may vary depending on the underlying cause, for example, if diabetes is responsible, your cat may drink and urinate more often. You may not notice your cat has a cataract until it is quite large and/or signs of poor vision become apparent such as bumping into walls, reluctance to climb stairs etc.
Some veterinarians will refer your cat to a veterinary ophthalmologist (eye specialist).
During the examination, your veterinarian will carefully check the eyes using an ophthalmoscope, and obtain a medical history from you. He may notice blue/grey spots on the eyes.
Your veterinarian will perform diagnostic tests determine the underlying cause which may include:
Complete blood count to check for infection or inflammation
Biochemical profile to evaluate how the organs are functioning
Ultrasound of the eye may be necessary if the cataract is too cloudy to examine the retina
Slit lamp examination involves the use of a special slit lamp to see the front of the eye under magnification
Electroretinogram (ERG) is a test which measures the electrical activity of the retina which helps to assess retinal function
The goal of treatment is to address the underlying cause as well as remove the cataract.
Incipient cataracts may require close monitoring only, to ensure they don’t grow in size.
Surgery is the most effective treatment for cataracts and involves removing the lens and replacing it with an artificial lens.
Phacoemulsification – Surgery to remove the lens. Prior to surgery, eye drops will be placed in the eye to dilate the pupil. A small incision is made in the cornea and a small opening is made into the capsule of the lens (capsulotomy) and an ultrasound probe emulsifies the lens which is then removed by suction. An artificial intraocular lens is inserted. The whole process takes under an hour.
Extracapsular lens extraction – Surgical removal of the entire lens if it is too solid to be break up, or the practice doesn’t have the necessary equipment for phacoemulsification.
In some cases, your cat may not be a suitable candidate for surgery, anti-inflammatory and/or antibiotic drops can relieve inflammation.
Anti-inflammatories and topical antibiotics are administered post-surgery to reduce inflammation and protect against post-operative infection.
Your cat will wear an Elizabethan collar during recovery to prevent injury to the eye.
Administer all medications as prescribed by your veterinarian.
Watch for signs of infection such as redness, swelling and pain.
Follow up appointments are necessary to monitor progress and check for glaucoma, a build up of intraocular pressure in the eye which can develop as a complication of cataract surgery.