Ординатура / Офтальмология / Английские материалы / The Eye Book A Complete Guide to Eye Disorders and Health_Cassel, Billig, Randall_2001

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surgery if you have worn them before or are interested in trying them (see chapter 5).

Similarly, the choice of various lens options is largely up to you. Options include antireflective lenses, polarized lenses, photochromic lenses (which change color when you move from a light area—like outside—to a darker area, and vice versa), and other tinted lenses. Many people experience visual discomfort from toobright sunlight and indoor light; antireflective coatings on lenses can reduce the glare and dazzle of lights, especially at night. (These lenses have also been helpful for people who play indoor tennis, where the lighting is often poor.) Ultraviolet protection in the intraocular implant lens or glasses after cataract surgery is felt to be important to protect the retina once the natural lens has been removed. (For more on lens options, see chapter 4.)

Some Questions You May Have about Cataracts

Do cataracts need to be “ripe” before they can be removed?

Although many years ago it was necessary for cataracts to mature to a certain stage before a patient could have cataract surgery, this is not true today. Modern microsurgical techniques have made it possible to remove cataracts at earlier stages of development based on the level of visual problems they are causing, not on their degree of maturity.

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What is phacoemulsification cataract surgery?

Phacoemulsification is an advanced cataract-remov- ing technique that uses ultrasound waves to shatter the cataract in the eye. Suction is then used to remove the lens fragments, making room for an implant lens. The tiny incision used in this technique either seals itself closed or requires only one stitch thinner than a strand of human hair. Most people recuperate quickly from this procedure and are able to resume their normal activities within a few days.

How can I find a good cataract surgeon?

Perhaps a better thought is “How to find a good doctor,” because a good cataract surgeon will have all the characteristics of a good doctor plus excellent surgical skills. In this case, good implies a skilled medical and surgical ophthalmologist who is caring and able to communicate well with patients. Whether you’re looking for an internist, dentist, or ophthalmologist, finding the right doctor for you can be the most important step.

Frankly, the ideal way to find the right doctor is probably not the Yellow Pages. Many doctors are also a little suspicious of their colleagues who promote themselves in newspaper, television, and radio advertisements. On the other hand, relatives and friends who have had cataracts or cataract surgery are usually excellent sources for referrals. Talk to your internist or family doctor too about the eye surgeons in your area.

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Finally, make an appointment to meet the eye surgeon, to decide for yourself. Ask to speak with some of the surgeon’s other patients with cataracts or who have had cataract surgery. Ask how often the doctor performs cataract surgery. This is extremely important. You don’t want someone who does this procedure only occasionally; you want someone who performs this surgery at least once or twice a week. Specifically, find out if he or she performs phacoemulsification, and if you are a candidate for this technique. Make sure that you’re comfortable with the surgeon’s postoperative care arrangement.

Remember, you have only one pair of eyes. And although cataract surgery is fairly safe these days, not all cataract surgeons are equal. A poorly performed or complicated surgery can cause you problems for the rest of your life.

I’m in a managed-care program. Will my program cover cataract surgery?

Cataract surgery is one of the most common health insurance services. The bottom line is that it costs insurance companies, and state and national health insurance programs like Medicare, a lot of money each year. As managed health care becomes more popular, there will be increasing pressure on doctors and hospitals to perform fewer cataract surgeries at lower levels of reimbursement. There has even been talk of only covering surgery on one eye! The choice of surgeon, facility, and time of the operation will also change from a patient-

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doctor decision to a health insurance company–dictated system. It is important to be aware of your health insurance coverage concerning your eye care, especially cataract surgery. Being informed about your options as a patient will help you get the care you desire when it comes time for cataract surgery.

If I have cataract surgery on one eye, how long do I have to wait to have the second eye done? Can’t I have both eyes fixed at once?

Anyone who would benefit from cataract surgery on both eyes should have two separate surgery dates. The time between operations usually averages about six weeks. Doctors rarely advise someone to have both cataracts operated on at the same time. For one thing, it’s helpful to leave one eye unoperated, to make it easier for you to see to get around after the operation. For another, any complications during or after surgery may change your surgeon’s approach when it comes time to operate on the other eye. And finally, depending on your experience with the first operation, you may decide you don’t even want to have the other eye done right away, if at all.

Can cataracts grow back after cataract surgery?

No, because the lens has been removed, and an artificial one has been implanted in its place. Occasionally, however, a cloudy film can develop behind the implant lens (see above). Ophthalmologists use state-of-the-art laser surgery to remove this cloudy film, thereby restoring the person’s vision.

8

Glaucoma, the “Silent Thief”

It’s often called the silent thief of vision.

One of the most troubling conditions to affect the eye, glaucoma indeed sneaks in, with the stealth of a master prowler. It rarely causes warning symptoms and yet is a leading cause of blindness—accounting for 12 percent of new cases of blindness each year in the United States. An estimated two out of every hundred people in the United States over age sixty-five have glaucoma. And it is estimated that half of those with glaucoma don’t know that they have it. Understandably, detecting and managing glaucoma is of major concern to eye doctors.

It is not a simple disease. In most cases glaucoma is instead a collection of eye problems that elevate pressure within the eye, damaging the optic nerve, and seriously affecting vision. Its onset is furtive, usually very gradual over several years; during this time people seldom have any symptoms to alert them of their elevated eye pres-

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sure. Most people who develop glaucoma can’t feel it. Even the loss of peripheral vision, one of the first signs of trouble, is so subtle that for many people it’s virtually unnoticeable. (Some people even develop optic nerve damage and visual field loss despite having normal eye pressures. More on this unusual form of glaucoma, called normotensive glaucoma, later in this chapter.)

One form of the disease, called acute closed-angle glaucoma, in which the pressure in the eye rises rapidly, does cause acute eye pain. This condition hits suddenly and is an ophthalmic emergency that requires immediate treatment. But it’s also pretty rare.

The more common form is called open-angle glaucoma. This is our old nemesis, the silent thief. Openangle glaucoma can advance undetected for years; during this time the constantly elevated eye pressure can cause irreversible vision loss by severely damaging the nerve fibers that pass through the optic nerve in the back of the eye. The nerve fibers most frequently damaged by this are those that make peripheral vision possible. Losing enough peripheral vision can, over time, lead to tunnel vision, in which people can see only when they’re looking directly ahead. In people with very advanced cases of glaucoma, this loss of vision can deteriorate into total blindness.

What’s your best protection against the potentially devastating consequences of glaucoma? Because its onset is so insidious, don’t trust yourself to notice early symptoms; chances are, you won’t. But your eye doctor will.

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This means that regular eye exams are essential! Only by monitoring the eyes regularly can glaucoma be detected early and managed well.

What Happens to the Eyes in Glaucoma

Think of the eye as a balloon. Inside the eye there’s a fine balance between the outer atmospheric pressure and the eye’s own internal pressure. This balance helps maintain the shape of the eye, or the balloon. Too much or too little internal pressure can easily change this balance.

Like a balloon, the eye is basically hollow, but it has an inner core that maintains its shape. This core is made up of two separate compartments, one filled with fluid and another filled with jelly. The front compartment, or cavity, of the eye is filled with a fluid called aqueous. Within this watery cavity (the aqueous cavity) are two areas, the anterior chamber and the posterior chamber, both of which are located in front of the lens. Behind the lens, the rear cavity (the vitreous cavity) holds a jellylike substance called vitreous.

Together, the aqueous and vitreous cavities help maintain the eye’s shape. While the vitreous, like jelly, is relatively inert and stable, the aqueous has a dynamic turnover with constant production of new fluid entering the eye and drainage of old fluid out—much like what happens in a storm drain. The big problem in glau- coma—the elevated pressure that damages the optic nerve—is caused when there’s a problem with the drainage. In keeping with our image of a storm drain,

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imagine the drain clogged by leaves, and the poor drainage—and water backup—that results.

Now for a little anatomy. The anterior chamber of the eye, which contains most of the aqueous fluid, is bordered by the back surface of the cornea and the front surface of the iris. The posterior chamber, which also contains aqueous fluid, is bordered by the back surface of the iris and the front surface of the lens.

The fluid itself is made by the ciliary body, eye tissue located near the root of the iris in the posterior chamber. It’s then pumped into the posterior chamber, where it circulates through the pupillary space and into the anterior chamber of the eye. The fluid drains out from the anterior chamber—and this is critical—at an angle, where the cornea and iris meet. (This is called the anterior chamber angle.) As it leaves the eye through this angle, the aqueous fluid passes through a filter of connective tissue called the trabecular meshwork.

The trabecular meshwork encircles the eye like a ring on a finger. Normally the anterior chamber angle is wide open, a straight shot to the trabecular meshwork, and the clear aqueous fluid freely exits the eye. It filters out through the trabecular meshwork into an aqueduct called Schlemm’s canal. Schlemm’s canal transports the fluid through a network of aqueous veins. The aqueous is then gradually absorbed into the blood supply by vessels in the conjunctiva.

Not a terribly complicated drainage system, but it’s got plenty of places for trouble to occur. When the flow of aqueous is interfered with somewhere along the route—

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from its beginnings, at the ciliary body, to the trabecular meshwork and Schlemm’s canal—the fluid backs up. And pressure within the eye—picture an overfilled water balloon—begins to rise. This, then, is the elevated pressure that can damage the optic nerve, gradually lead to nerve death and loss of peripheral vision—if, that is, the pressure is not lowered by treatment.

Types of Glaucoma

The type of glaucoma—there are two basic forms— depends on the specific obstruction that’s hampering the aqueous fluid’s drainage from the eye. Closed-angle glaucoma (also called narrow-angle glaucoma or angle-closure glaucoma) results when the fluid’s access to the trabecular meshwork is physically blocked by the root of the iris. The more common condition, open-angle glaucoma, happens when, despite an open drain in the anterior chamber angle, the trabecular meshwork filter itself is somehow clogged. Note: Unfortunately, it’s possible for someone to develop a combination of both types of glaucoma in the same eye.

Closed-Angle Glaucoma

The problem with closed-angle glaucoma is an obstruction in the drainage of aqueous fluid due to a narrowing in the angle of the anterior chamber. This anatomical defect can best be seen during a comprehensive eye examination with a technique known as gonioscopy, using a specially designed contact lens with an-