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Extracapsular lens extraction in cats is a specialist, surgical procedure on the eye. The aim is to remove the inner part of the lens (the nucleus and cortex) whilst leaving behind the lens capsule. A replacement lens is then inserted into the empty capsule, in order to restore vision.
The goal of treatment is to remove a diseased lens, most commonly affected by cataract formation, and replace it with a new, artificial lens in order to help the cat see again.
This is a specialist procedure requiring special equipment. Those patients requiring extracapsular lens extraction will be referred to a specialist veterinary ophthalmologist by the first opinion vet.
The cat must be carefully assessed ahead of the procedure, to ensure the retina is intact and undamaged. In cases where there is retinal damage, then extracapsular lens extraction will not restore vision and the procedure is not warranted.
Once the cat has been screened and it is confirmed the retina is functioning normally, the cat is prepped for surgery. This involves a full general anesthetic. The surgeon works using magnification and miniaturised instruments, and the eyelids are held open with retractors.
Drops are applied to the eye in order to dilate the iris to its maximum. A small incision is then made in the cornea and a fine probe passed into the anterior chamber and advanced into the lens. A procedure known as phacoemulsion then takes place.
Phacoemulsion utilizes high frequency ultrasound waves to break up the diseased lens from inside the capsule. The lens fragments are simultaneously aspirated up and out of the lens capsule via the probe head.
Once both the nucleus and cortex have been liquidized and removed, the surgeon carefully injects a replacement lens into the vacant capsule. This lens inflates once it is in place.
When the surgeon is happy with the position of the new lens, the cornea is sutured using ultra-fine absorbable suture material, and the cat woken from the anesthetic.
Extracapsular lens extraction can permanently restore eyesight in cats that were blind due to cataract formation.
Older techniques involved making a larger incision in the cornea and a special scoop-like instrument to scrape out the nucleus and cortex. The technique is still used for human cataract operations with great success in third world countries.
Unfortunately, there are no medical alternatives that might successfully reduce the opacity of a cataract, therefore surgery is the patient's best option for better vision.
Strenuous activity or rubbing of the eye could damage the suture line, and must, therefore, be avoided. The cat must wear a cone to prevent pawing the eye. Drops are applied several times a day to prevent infection and reduce inflammation. The cat should be restricted and encouraged to rest.
Non-steroidal painkillers such as meloxicam may be prescribed for several days after surgery, in order to reduce postoperative discomfort.
Extracapsular lens extraction is an expensive procedure. It is likely to be more costly in diabetic cats because of the increased monitoring needed whilst the cat is anesthetized and in recovery. The fees also vary depending on whether one or two eyes are being operated on.
For a single eye the cost is around $1,800 to $2,200 and for two eyes $2,800 to $3,600. This does not include the cost of screening tests to ensure the retina is healthy, which can be around $200.
There are risks associated with extracapsular lens extraction such as infection and wound breakdown. In the worst case scenario this could mean the loss of the eye. However, in the hands of a skilled specialist, most cases do well and go on to recover uneventfully. The cat owner also has a part to play in their pet's recovery, by vigilant application of drops and prevention of trauma to the eye.
A successful procedure can restore lost vision and make a big difference to the cat's quality of life.
The most common cause of cataracts in cats is diabetes mellitus. The symptoms of this include thirst, wetting more often, and weight loss. The owner should be alert to these clues and seek veterinary attention for their cat at the soonest opportunity. Prompt diagnosis and management of the diabetes can delay serious cataract formation.
Likewise, obesity plays a big part in the development of diabetes in cats. Keeping the cat at a lean weight goes a long way to preventing diabetes from occurring in the first instance.
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