IT HAPPENS to more than a million persons each year. The problem affects twice as many women as men. It usually occurs when persons are in their sixties but can happen at any age, even before birth. What are we talking about?
Loss of vision through cataracts. You have often heard of cataracts, but do you really know what they are? What can be done to restore vision once cataracts develop? Let us begin by taking a closer look at your eyes.
The eyeball is a complex, three-dimensional, full-color motion-picture camera. It is shaped like a sphere and, for the most part, is filled with a jellylike transparent substance called vitreous humor. Encasing this semiliquid substance is a three-layered “skin.” The outer layer is known as the sclera, the middle one is the choroid and the inner layer is the retina. But none of these three layers encircle the entire eyeball. They all leave space at the front.
In the forepart of the eyeball the sclera merges into a convex transparent tissue called the cornea. It is shaped somewhat like a tiny bowl placed at the front of the eye with the bottom facing out. Behind the cornea is the iris, a thin circular curtain of muscular tissue that constitutes the colored part of the eye. The iris has a hole at its center, known as the pupil. Two sets of muscles in the iris can change the size of the pupil, controlling the amount of light that enters. Filling the space between the cornea and the iris is a clear fluid called aqueous humor.
Do you realize that actually your eyes do not ‘see’ anything? Instead, they bend and focus rays of light, which the optic nerve (attached to the rear of the eyeball) transmits to the visual center of the brain. To make that possible, the eye has another major part.
Just behind the iris is a transparent crystalline lens, which is about the size of an aspirin tablet. The lens is biconvex, that is, it is convex at both its front and back. The cornea and the lens work together to bend light rays and focus them at the back of the eyeball on the inner of its three surrounding layers, the retina. A group of muscles attached to the lens can make it change shape so as to bring things into focus. A cross-section view of the lens would reveal that, when focusing on a distant object, it is oval-shaped like a football. The lens would appear rounder when the eye views something up close.
Aging and Cataracts
It is in the lens that cataracts develop. They cause clouding of the lens and may spread until the entire lens loses its transparency. The word “cataract” comes from a Latin term meaning “waterfall.” This is because it appeared to ancient physicians that a veil of blurry water had fallen over the lenses of persons who had cataracts.
Some people think that cataracts are growths that form on the lens. However, Dr. David K. Berler points out: “A cataract is not a growth, or something new to the eye; it’s merely a change in clarity of the normal lens.” What causes this?
The reasons for cataracts are not well known. But a factor nearly always present is aging. The lens of your eye is not solid like a piece of glass, but is a living organ that continues to grow throughout your life. Like an onion it is composed of many layers of cells. As new layers form, those beneath them become compressed, dehydrated and stiff. With the passing of time proteins in the nucleus of the lens can undergo changes that cause it to become deep yellow, brown or sometimes nearly black. Or, fibers in the many layers of cells surrounding the nucleus may become swollen or distorted, resulting in formation of gaps filled with fluid and debris. All of this scatters light, blurring vision.
Other Causes
However, aging is not the only cause of cataracts. A defect in your body’s ability to utilize sugar may be implicated. According to one study, persons with diabetes proved to be four to six times more likely to develop cataracts than nondiabetics of the same age and sex. What is the reason for this? An article appearing in Scientific American of December 1975 noted that diabetes results in a raised level of glucose in the eye’s aqueous humor. This triggers a chemical reaction that produces the sugar alcohol “sorbitol” in the lens. The consequent increase of pressure within lens fibers causes them to take up water from the aqueous and vitreous humors. As a result, the lens fibers become swollen and disrupted, eventually leading to loss of transparency.
Other causes of cataracts can include a drastic change of diet leading to deficiencies of certain vitamins or other elements of good nutrition. Traumatic cataracts result from a blow to the eye or the piercing of the eye by some sharp object, which dislocates and damages the lens. According to the book Living with Your Eye Operation, cataracts can result also from the effects of “ultraviolet light, X-ray, infrared (heat), and other kinds of radiation, including microwaves from ovens, radar, and diathermy.” This publication therefore suggests that people wear goggles or sunglasses to filter out harmful rays when using sunlamps or other equipment that emit eye-damaging radiation.
Can You Avoid Prolonged Vision Defects?
While no one can assure that you will never develop cataracts, there are steps that you can take so that you will suffer only minimal impairment of vision from them. How so?
It has been noted that in many cases a diet rich in vitamins A, B (especially B2, or riboflavin) and C has been effective in retarding development of cataracts. Might such a diet help you? If you are a diabetic, be sure not to neglect the disease. Proper management of diabetes can help you to avoid serious complications that may lead to cataracts.
When approaching the age when cataracts are most likely to develop, it makes sense to have regular eye examinations. In an interview published in U.S. News & World Report, Dr. Carl Kupfer, director of the National Eye Institute, offered this advice:
“We assume that every child has an eye examination at birth to pick up congenital defects. Next would be an examination during the age of 3 1/2 to 4 1/2. Then, if there are no problems, I would wait until the child enters puberty.
“After that, if a person is not having any symptoms of trouble, I don’t think routine checks are necessary until the mid-40s period. After that time until about 60, a person should see an eye doctor at least every two years, because he or she is going to need a change of glasses as close-up vision suffers.”
Have you had an eye examination recently?
The most common treatment for cataracts is surgical removal of the clouded lenses. However, in some cases it may be possible to forestall surgery for a period of time and yet retain good vision. In rare instances, for example, the cataract is very small and near the center of the lens. Therefore the doctor can prescribe drops that will enlarge the pupil. This allows light to enter the edges of the lens, enabling one to ‘see around’ a cataract. In other cases, also very rare, cataracts may form around the edges of the lens while its center remains transparent. If this happens, special glasses or contact lenses can serve to direct more light toward the center of the lens.
But what if the only way to restore your eyesight is to resort to surgical removal of the lens? Is it a dangerous, painful operation? What would be your prospects for regaining good vision?
“Ninety-eight Percent Successful”
“Cataract removal is the most successful blindness-prevention operation,” notes the book Living With Your Eye Operation, adding: “Today cataract removal operations are about ninety-eight percent successful. Testimony to their rate of success is the staggering statistic of a quarter of a million cataract operations performed in the United States every year. . . . About eighty-five percent of all persons operated on for cataract achieve normal vision (20/30 or better).”
The operation itself is not overly painful. Usually the patient is put under mild sedation when brought to the operating room. He is awake but tranquil. Then small injections are given to anesthetize the eye muscles. After that the doctor proceeds to extract the cataractous lens. How does he accomplish that?
After spreading apart the eyelids, the doctor makes a small arc-shaped cut where the white part (sclera) of the eye meets the upper part of the iris. Then the cornea can be folded down, giving access through the pupil to the lens. Some surgeons remove a small section of the iris too. A special enzyme serves to dissolve the fine “zonules” that grip the I lens, making it easier to extract.
There are different methods of removing the lens. Some surgeons use tweezer-like forceps. Others employ a cryoprobe, which is a small probe attached to a freezing unit that keeps the tip at about 15 degrees Fahrenheit (-9.4 degrees Centigrade). This freezes the lens so that it adheres to the probe and comes out gently in one piece. When the lens is gone, the void is filled with saline solution, which helps the eye to maintain its proper shape and internal pressures.
Another method of lens removal is phacoemulsification. This involves a special probe that pierces the lens. Dr. Berler explains: “This probe vibrates about 40,000 times a second, shattering the cataract, which is then sucked out in fragments through a very fine tube. A second tube injects fluid into the eye, so that there is a constant circulation of fluid going in and debris going out.” An advantage of this procedure is that only a very small incision is necessary to admit the special vibrating probe. It can be closed up with a single stitch and the patient may be able to leave the hospital the same day or shortly thereafter.
After the Operation
An operation to remove cataracts, however, leaves the eye without a lens to focus sharp images on the retina. What compensates for this?
Special eyeglasses are the most readily available replacement for missing lenses. However, cataract glasses are very thick. Besides being heavy, they magnify everything some 25 to 30 percent, making things appear closer than they really are. And there is a great deal of distortion at the edges. When looking to the sides or up and down, a person wearing cataract glasses must learn to turn his head, rather than just his eyes.
Much of this problem disappears with contact lenses. Their magnification is much less; and since they adhere closely to the cornea, contact lenses move with the eyes, eliminating the need for exaggerated head movements.
Some researchers have developed plastic lenses that go right into the eye, replacing the normal lens. One type fits in the same location as the original lens. Another type is positioned in front of the iris. However, plastic lenses cannot change their shape to focus on objects at varying distances.
Has your vision become blurred? Could the problem be cataracts? If so, a relatively simple and painless operation along with corrective lenses is likely to restore good vision. Is it not worth a visit to your eye doctor to find out?
