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

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there’s a good chance that your vision will be improved by it. If the retina or the optic nerve isn’t healthy, then rarely will the removal of a cataract improve someone’s visual acuity. (Imagine trying to focus light rays in a camera onto bad or exposed film. The lens can be as clear as possible, with the best focusing ability, but none of that will matter if the film is simply bad.)

Before performing cataract surgery, it’s essential for the doctor to assess the health of the rest of your eye behind the cataract. This requires carefully going over your medical history, asking many questions about past vision problems, eye trauma, and eye disease. Your doctor may use instruments such as a potential acuity meter (PAM) to test the health of your eye behind the cataract. In this test, a visual acuity chart—similar to the classic ones you see in an eye doctor’s office—is projected through the cataract and focused onto the retina in the back of the eye, using two pencil-thin beams of light. If someone can see the chart better this way, then the retina is usually judged as healthy. If, on the other hand, the person can’t see the PAM test chart on the retina, this implies that the retina or the optic nerve may not be healthy, and it’s doubtful whether removing the cataract would improve vision. (Note: Sometimes the PAM test can provide misleading results. Therefore, it should be done by doctors who have a great deal of experience using these instruments and interpreting their results.)

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What about the Risks?

We’ve talked about the benefits of cataract surgery (improved vision); we also need to consider the risks. Many people hear from their friends how easy it was to have cataract surgery, and because the surgery is relatively safe these days, fewer people have heard about those who had complications. But cataract surgery is an operation. As with any operation, there are risks, and there is a recovery period.

One risk of cataract surgery is an eye infection. Many surgeons give their patients antibiotics around the time of surgery, in theory to help lower this risk—although studies have yet to prove this rationale. (Some patients may be given antibiotics before surgery.) Another big concern is retinal detachment, during and after cataract surgery. The retina is like wallpaper lining the back of the eye. If there’s any weakness in the retina at the time of surgery, it can become detached, like peeling wallpaper, from the back of the eye. This is why people are examined frequently after the operation. If a retinal detachment occurs, it is repaired right away. (We have also seen patients sneeze their implants out of place, rub open their cataract wounds, and even fall on their eyes soon after cataract surgery.)

Many other complications are also possible, either during or after cataract surgery. Any surgeon who performs cataract surgery sees these complications; fortunately, they’re infrequent—on the order of 5 to 10 per- cent—but they do happen. This is where the experience

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and competence of your surgeon can make all the difference in the world. Usually, if complications are recognized and treated early, the eye can still heal well after surgery and achieve improved vision—even if this requires a second surgery soon afterward. If an infection gets out of control or a retina becomes very badly detached, however, there’s a chance that the vision in the eye could end up worse than it was before the operation. In rare cases, people have lost an eye from cataract surgery. In extremely rare cases, people have had unforeseen reactions to anesthesia and have even died from it. Fortunately, complications of all kinds are unusual, and most cataract surgery goes very well. But it’s worth repeating that cataract surgery, no matter what you’ve heard from friends, is not without some discomfort, and a good outcome is certainly not guaranteed.

How’s Your Health in General?

Your overall health is another important consideration. Although today, with modern microsurgical techniques, cataract surgery is relatively safe, with few complications, there are still risks. People taking Coumadin, aspirin, and other blood-thinning medications are at risk for excessive bleeding during the operation. Because it’s necessary to lie flat during the operation for a period of time ranging from as little as fifteen minutes to greater than an hour, someone with severe scoliosis, debilitating arthritis (especially in the cervical spine), or chronic obstructive pulmonary disease may have difficulty.

Also, a certain level of patient cooperation is necessary

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if something goes wrong? Could I be blinded? How long will it take after the operation for me to drive, get back to work, read, and resume my other normal activities? Will the other eye need cataract surgery in the near future?

The stakes are much higher for people who have only one working eye, since for them an unsuccessful operation can have a much graver outcome; the risks of surgery for these individuals become magnified and potentially devastating.

There’s no master list of answers to these questions, because everybody’s situation differs slightly; in fact, there are as many sets of preand postoperative cataract surgery instructions as there are eye surgeons. But one standard applies in every case: You should feel free to raise your concerns and questions with your cataract surgeon and his or her staff before surgery, not only to ease your worries but to establish realistic expectations regarding this procedure. If your surgeon flunked the bedside-manner course in medical school, and either doesn’t fully answer your questions or concerns or doesn’t seem inclined to take the time to listen to you, you may want to seek a second opinion or consider going to a different surgeon altogether. You should also be comfortable with your surgeon’s arrangements for your postoperative care. Today not all cataract surgeons follow their patients after surgery, instead sending patients back to their ophthalmologist or optometrist for postoperative management.

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Cataract Surgery

Cataract surgery has progressed remarkably over the last thirty years. Not too long ago people routinely spent a week or two in the hospital recuperating from a cataract operation. At that time the hazy cataract lens was removed using mainly manual techniques. Sand- bags—how primitive it seems now!—were placed around the patient’s head in an attempt to prevent movement while the wound healed. The results of these procedures varied, and there were much higher rates of infection and inflammation following surgery than we see today. Furthermore, after cataract surgery many people had to wear thick cataract glasses that overmagnified and distorted their vision.

Welcome to the microsurgery revolution. Special microscopes, designed to give ophthalmologists a better view of the cataract and other eye structures during surgery, have enabled us to refine our surgical incisions and other delicate procedures performed inside the eye. As microsurgery has evolved, surgeons have developed many new instruments for use within the eye. And new sutures, finer than human hair, and smaller cataract incisions have allowed for better wound closure following cataract surgery. This advance too has speeded the patient’s recovery, and it’s also helped us maximize the chances for achieving good vision after the procedure.

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Intraocular Lens Implants

The lens provides focusing power for the eye. When it’s removed, as it is during cataract surgery, the eye loses its ability to focus properly. So, the dilemma: how to fix one problem (getting rid of the hazy lens) without creating an even bigger one (removing someone’s ability to focus incoming light rays, and therefore see in that eye, altogether).

Years ago the most widely accepted options for correcting this lack of focusing power in the eye after cataract surgery were the thick cataract glasses or contact lenses mentioned above—inadequate solutions, both of them. Many people found it difficult, if not impossible, to adjust to the distortion and magnification created by the thick glasses. And contacts weren’t an ideal option because they were difficult to handle, especially for people with arthritis or a mild tremor; they also increased the risk of developing an eye infection.

Eye surgeons continued to search for a more acceptable option for returning focusing power to the eye, eventually developing an artificial lens, or intraocular lens implant. This implant, which can be placed in the eye during cataract surgery, restores some of the eye’s ability to focus after the old lens has been removed. In addition to the lens implant, you may also need a pair of normal reading glasses to provide more focusing power for close work, or a bifocal prescription that will also finetune your distance vision. Although they don’t create perfect vision, intraocular implants have eliminated the

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magnification problems created by those thick cataract glasses and have helped many people avoid the difficulties associated with the use of contact lenses. After cataract surgery, you can still wear contacts if you want to.

A Bit of Background

A complete history of intraocular implant lenses is beyond the scope of this text (and is in fact the subject of several books). But the story of their development is an interesting one. Dr. Harold Ridley, an English ophthalmologist working during World War II, is credited by most people as the person responsible for originating the idea of implant lenses in cataract surgery. During the war he treated many Royal Air Force pilots who had been injured when their planes’ cockpits shattered. In a number of these pilots, cockpit fragments had penetrated the cornea and lodged in the anterior chamber of the eye. But surprisingly, Dr. Ridley noticed, these fragments were actually well tolerated by the eye! This gave him the idea that a prosthetic lens could be developed of similar material and placed in the eye after removal of a cataract.

As you might expect, early attempts to create implant lenses met with many problems and complications, since manufacturing techniques and materials were limited. Glass implants were too heavy and would not remain properly fixed in the eye. But over the years technology finally caught up with the idea, and newer implant designs were of plastic—which, as with contact lenses, eventually became the material of choice. Surgeons tried various methods of getting these implants to stay put in-

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side the eye; all met with varied success. After many years of study we have found that it’s best to place intraocular implant lenses behind the iris inside the old cataract bag, where they’re better ensconced and in a better position for the restoration of eyesight.

Just like transistor radios, implants have gotten smaller over the years as our technology and surgeons themselves have become more sophisticated. Now, thanks to better surgical instruments, it’s possible to remove a cataract through narrower incisions—and the finer the incision, the more rapidly someone will heal after cataract surgery. Also, these smaller wounds are less likely to induce unwanted astigmatism in the eye, a common problem after cataract surgery. We continue to strive for ever-tinier incisions and implant lenses. Currently the trend is to make a 3-millimeter incision and use foldable implant lenses. But who knows what the future holds—perhaps a needle-sized incision and an injectable implant?

Advances in Anesthesia

The major surgical advances, the new, highly sophisticated equipment, plus an expanded spectrum of medications to decrease infection and inflammation after the operation have helped make cataract surgery a much safer and more effective procedure. Because of improved techniques, cataract surgery today is usually done under local anesthesia (instead of general anesthesia, which carries more risks). As noted earlier, you’ll probably receive a relaxing medication, given by intravenous injection,

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before the procedure to make you sleepy. Then you may be given injections of a local anesthetic around the eye to decrease sensation and movement (similar to the injections the dentist uses when working on your teeth). Patients are usually in a “twilight sleep” during surgery, aware but not caring; these injections also block your vision in that eye during cataract surgery. Some doctors today even choose to perform cataract surgery using only topical anesthetic eye drops. This may be supplemented with an intraocular anesthetic, but either way requires a very cooperative patient to keep the eye from moving during surgery.

Improved techniques of closing the incision and new ways of controlling inflammation have done away with those prolonged stays in the hospital patients used to endure (remember the sandbags!). In fact, most cataract surgery today is done on an outpatient basis: patients have their surgery and then go home the same day.

Before Surgery

The A-Scan Measurement

The A-scan measurement, an ultrasound measurement of the length of the eyeball, is an important calculation that must be performed before surgery to help de- termine—along with other measurements such as your eyeglass prescription in each eye, corneal curvature readings, and the intraocular lens constant—the appropriate power of the lens implant you’ll be getting. Unfortunately this calculation is not always as accurate as we