Common Surgical Procedures - Eye surgery
Among common types of eye surgery are procedures for correcting eye muscles, glaucoma, cataracts, cornea and retina disorders. Operations on the eye muscles are intended to correct crossed eyes or similar problems in which the two eyes fail to work together.
The condition technically known as strabismus , in which one eye drifts so that its position is not parallel with the other, is caused by a congenitally weak muscle. Infants often appear to have crossed eyes, but in most cases the drifting corrects itself by the time the baby is six months old. If the condition persists beyond that time, a physician should be consulted. He may recommend the use of an eye patch over the stronger eye so that the weaker one will be exercised. If this does not achieve the desired result, he may prescribe special glasses and eye exercises as the child gets older, so that there is no impairment of vision.
If corrective surgery proves necessary after these measures, it is usually done before the child enters school. The operation is a simple one involving the muscle and not the inside of the eye itself. Each eye has six extraocular muscles—muscles originating outside the eyeball—to move the eye up, down, left, right, etc.; the surgeon lengthens or shortens these muscles, as may be required, to coordinate the eye movements. The operation is safe and requires only a brief hospital stay.
If the lack of eye coordination is not corrected, a kind of blindness called amblyopia can result in one of the eyes. This condition occurs particularly in young children who depend upon the vision of one good eye; the function of the other eye is allowed to deteriorate. It has been estimated that about two million Americans have lost a part of their vision in this manner. Crossed eyes should receive professional attention early enough to prevent a permanent visual handicap.
Cataract is a condition in which there is a loss of transparency of the lenses of the eyes. Each lens is made up of layers of cells naturally formed to focus a visual image on the retina at the rear of the eyeball. As a result of aging, or because of an injury to the eye, the lens may develop cloudy or opaque areas, or cataracts , that result in a blurring of vision. About five percent of the population of the United States have cataracts. Some physicians claim that anyone who lives long enough can expect to have cataracts, although age is not the only determining factor.
The condition can be corrected rather easily by several different kinds of surgical procedures. Among these, a relatively simple, advanced technique involves a microsurgery procedure called extracapsular extraction followed by implantation of a new lens. Using this method, the surgeon first makes a tiny incision in the cornea. Reaching through that incision, the surgeon then makes a circle of tiny cuts in the lens. The lens and its cataract are then drawn through the opening in the cornea. The back part of the lens remains in place to support the implant lens.
Extracapsular extraction has begun to replace older techniques. These include dissolving the tissues holding the lens in place with a liquid enzyme, freezing the lens with a supercold probe, and grinding the lens tissue with a high-speed instrument. Extracapsular extraction requires only a local anesthetic injected into the facial muscles. Because the sutures are tiny, healing time can be as short as a few weeks.
Laser surgery has also been used effectively following cataract lens replacements. The neodymium yttrium-aluminum garnet (Nd:YAG) laser has helped to clear the capsular membrane that sometimes clouds the eye after such surgery.
The timing of cataract surgery presents the patient with a difficult decision. To help you make up your mind, the physician may use a potential acuity meter (PAM) to show what kind of vision you should have after a cataract is removed. The PAM projects a light beam that flashes a standard eye chart through tiny clear areas in the cataract. Because the beam hits your retina directly, you can read the chart without interference.
Lens implants normally effect greatly improved vision. But for optimum results most patients need to wear eyeglasses or contact lenses after the operation. Because implanted lenses cannot focus as your eye's natural lens does, you will probably need reading glasses. The artificial lenses may require some adjustments to compensate for visual illusions as to distances and shapes, but the blurring of progressive blindness will have been eliminated.
Sometimes after cataract operations, patients notice that the rear part of the lens left in to support the implant has begun to cloud. In such a case a surgeon may use a laser beam to punch a tiny hole in the clouded area. The hole lets light rays reach the retina unimpeded.
The cornea of the eye is a clear window of several cells in thickness at the very front of the eye. While it is protected by the constant sweeping of the corneal surface by the eyelid and the washing of the surface by the tears, it is vulnerable to injury and infection, allergies, and metabolic disorders. The simple habit of rubbing the eyes can distort the shape of the cornea, changing the normal round shape to a cone shape. Eventually, a cornea may degenerate from wear and tear and become so clouded that the patient can no longer see clearly, if at all. It is possible, however—and has been since the 1930s—to replace a clouded cornea with an undamaged cornea from a deceased person. Corneas are contributed by donors and stored in eye banks.
When only a portion of the cornea needs to be replaced, as is often the case, a disk encompassing the damaged cornea is carefully cut out and a piece of new cornea of precisely the same size and shape is sewn into the remaining tissue of the old cornea. The reconstructed cornea is treated with antibiotics and bandaged for several weeks. More than three-fourths of the cornea transplants are successful; the chances of success depend upon many factors, including the health of the remaining tissues of the original cornea.
Glaucoma, a leading cause of blindness, is a disease caused by a failure of the fluid produced inside the eye to drain properly. The fluid, or aqueous humor , is produced in the anterior chamber of the eye, between the cornea and the lens. In a normal eye it drains through a duct at the base of the cornea at the same rate at which it is produced. But if the drainage system is obstructed, fluid buildup creates pressure backward through the eye. If untreated, such pressure can cause gradual blindness by crushing the nerves at the back of the eye.
Some cases of glaucoma can be treated with medications that control the rates of fluid production and drainage. But when medications are no longer effective or when an acute attack occurs, with symptoms of severe eye pain sometimes accompanied by abdominal pain, nausea, and vomiting, surgery within a matter of hours is recommended. Several surgical procedures for the treatment of glaucoma are available; all are designed to release the fluid pressure in the eye. One common procedure involves cutting a small opening in the iris. Another technique is to insert a fine wire into the duct that normally drains the fluid and literally ream it open.
Other surgical and nonsurgical treatments for glaucoma have been developed. For example, laser surgery has proved effective for treating both open-angle and closed-angle glaucoma. In the former, the eye's internal drain system does not work properly, causing pressure to build up in the eye. In closed-angle glaucoma, fluid cannot pass properly from the front to the back of the eye, again producing dangerous pressure. The neodymium yttrium-aluminum garnet (Nd:YAG) laser is usually used in treatment to “drill” a tiny hole and destroy swollen blood vessels that block normal fluid drainage. Because marihuana has also been found to reduce pressure in the eye, manufacture of the chemical known as THC (delta-9-tetrahydrocannabinol), the key marihuana ingredient, was authorized by the Food and Drug Administration in 1985 and begun in 1986. THC has also been used to relieve the nausea accompanying cancer chemotherapy and to slow multiple sclerosis.
An estimated 10 million people in the world are afflicted by glaucoma, and the chances of developing increase with age. Women are twice as likely to develop the disease as men, and there is some evidence that the risk is hereditary. However, it also is easily preventable and controllable, since glaucoma usually develops slowly and can be detected during routine eye examinations in its early stages.
Retinal Detachment or Disease
Retinal detachment can occur from bleeding in the retinal area, an injury, a change in the shape of the eyeball, or other causes. The surgical treatment to correct the problem usually is related to the specific cause. For example, if fluid or blood has accumulated behind the retina, it is drained away. Alternatively, pressure may be directed within the eyeball to push the retina back into its proper position. For some cases, such as those associated with diabetic retinopathy , a kind of retinal bleeding in diabetes patients, a laser beam is used to seal the blood vessels responsible for the tiny hemorrhages in the eye.