A cataract is the lens inside the eye that has lost its clarity. As the lens becomes cloudy, vision gets worse. At some point, the loss of vision becomes great enough that an individual is willing to have an operation to improve the vision. The surgery is a cataract extraction. In this procedure, the cloudy lens is removed from the eye. In most situations, an artificial lens, called a lens implant, is placed inside the eye to take the place of the natural lens that has been removed.
In order to understand the different types of cataract operations, one needs to know about the structure of the lens. The crystalline lens inside the eye has several parts. The center of the lens is a hard core called the nucleus. The lens nucleus is made up of rings of cells, pushed together over time, similar to the rings in the trunk of a tree. The nucleus starts out very soft in childhood, but gets progressively harder with age. Surrounding the nucleus is the lens cortex. The cortex is a softer material. The entire lens is enclosed by the capsule that is similar to a clear bag. The lens is held in place by small fibers call the zonule.
A cataract operation is usually done with a local anesthetic. This means that medicine is used to numb the eye so that the patient feels no pain. The patient is usually awake during the operation.
There are several different techniques for removing a cataract. They are divided into two groups: intracapsular and extracapsular. One common misunderstanding about cataract surgery is that it can be done with a laser. A laser is a tool that is used commonly in eye surgery, but it cannot be used to remove cataracts.
In an intracapsular cataract operation, the entire lens is removed with its capsule. A large opening is made in the eyeball. A special medicine is injected into the eye that causes the zonular fibers to dissolve. Then, a special instrument is placed on the lens. Liquid nitrogen is used to cause the instrument to freeze to the lens. When the lens is frozen to the probe, the lens is gently pulled out of the eye. Many stitches are necessary to close the eye until it heals.
Intracapsular cataract operations are now rare. They were the most common type of cataract surgery until the early 1980s. Now, extracapsular cataract extraction is the method of choice for removing a cataract, except in very unusual conditions.
The difference between the two operations is that in an extracapsular cataract operation, part of the capsule is left inside the eye. A smaller opening is made into the eye. Then, an opening is created in the front of the capsule, large enough for the nucleus of the lens to be removed. The nucleus can either be removed as a whole, or it can be dissolved into tiny pieces and vacuumed out of the eye in a technique called phacoemulsification. Then, the cortex is also sucked out of the eye, leaving just the back part of the capsule to remain. Depending upon the type of operation, stitches may or may not be necessary to close the eyeball.
In either type of operation, after the natural lens is removed, the lens implant can be inserted into the eye. Most of these lenses are made of a hard plastic material. Recently, some newer types of material such as silicone and hydrogels have been used. In an intracapsular cataract operation, the lens implant is placed in front of the iris, the colored part of the eye. In an extracapsular operation, the implant is placed behind the iris, the lens' natural position. This is only one of many advantages to the extracapsular approach to surgery.
After cataract surgery, glasses are usually worn to fine-tune vision. With a lens implant in the eye, the vision is close to normal, even without glasses. If a lens implant is not used, much thicker glasses may be necessary.
Any operation has benefits and risks. The benefit of cataract surgery is improved vision. The results of surgery, however, cannot be guaranteed. Any operation can have complications that can affect the outcome. If a problem develops during or after cataract surgery, vision might not improve. It is even possible to lose all vision if a severe problem occurs. In general, cataract surgery is usually safe and successful. On average, 95% of people that have the operation in this country have a good result.
PLEASE NOTE: The information contained on this system is not intended to supplant individual professional consultation, but is offered as a community education service. Advice on individual problems should be obtained directly from a professional.
Copyright, 1994. Richard E. Gans, M.D.
Last Modified: August 23, 1996