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

7

Cataracts

It’s probably cataracts. My friend’s aunt had cataracts, and so did her husband. I’m the right age for it, and I’m having problems with my eyes—cataracts, that’s it. I bet I need surgery.

Well, you may. Then again, you may not—depending on whether you do indeed have cataracts. Although cataracts are probably the most talked-about eye problem today and a major reason for visits to an eye doctor as we get older, they’re also—right up there with astig- matism—among the most misunderstood disorders of the eye.

Difficulty reading for prolonged periods of time, excessive tearing, occasional feelings of having something in your eye, double vision in both eyes, pain in or around the eye—these are not typical symptoms of cataract development. (Of course, if you’re having any troublesome eye symptoms—whether you think the diagnosis is cataracts or not—you should seek medical attention.)

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What Are the Symptoms of Cataracts?

Symptoms associated with cataracts include:

•Impaired distance vision

•Blurred vision

•Frequent changes in eyeglass prescriptions

•Poor night vision

•Glare

•Appearance of a halo around lights

•Need for ever-brighter lights for reading

•Double vision in one eye

Instead, cataracts more commonly cause problems with distance vision, blurred vision, frequent changes in eyeglass prescriptions, and poor night vision; they can also cause glare, make it appear that there’s a halo around lights, and make it necessary for the person to use everbrighter lights to see to read. Our goal with this chapter is to help you understand about cataracts, their development, symptoms, and treatment, and to help give you realistic expectations about what their surgical removal can and cannot achieve.

The first thing you need to know is that if you have developed cataracts, you couldn’t have picked a better time to do it. Not long ago cataracts were removed through large incisions in the eye. These surgical wounds were closed with thick sutures that caused a lot of pain and swelling. Also, intraocular implant lenses were in their in-

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fancy just twenty to thirty years ago; before this, cataract patients had to wear thick cataract glasses or extendedwear contact lenses. Today, thanks to great surgical advances, things are dramatically different. Most people with cataracts who need surgery undergo the modern phacoemulsification procedure, which enables surgeons to remove the cataract through a tiny incision in the eye. Complications are fewer, and recovery time is quicker. Now more than 99 percent of patients who undergo cataract surgery receive a permanent implant lens for better focusing power and sight.

What Is a Cataract?

A cataract is an opacity or haziness that develops in the eye’s lens. For most people a cataract simply develops as part of the normal aging process. All people over age sixty-five have at least some degree of cataract development; although this aging process usually affects both eyes at the same time, it can progress at different rates. Just because you’ve never been told that you have a cataract doesn’t mean that you don’t have some degree of cataract development in your eyes. Cataracts are somewhat like gray hair and wrinkled skin in this regard: everyone eventually gets some of these changes, but we really don’t take notice or make mention of them until someone has a lot of gray hair or wrinkled skin (and ideally even then we’d hold back, just to be polite!). Similarly, most eye doctors feel that cataracts are hardly worth mentioning at the beginning. However, rest assured that we

Image not available.

Fig. 7.1. The parts of the lens

Image not available.

Fig. 7.2. Types of cataracts

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become acutely interested in them as they progress and begin to affect vision.

Many people ask if a cataract is actually a film, like the skim on fresh milk, or maybe a sheet of algae on a pond, growing on the eye’s surface. Actually, no. A cataract occurs in the lens, which is deeper within the eye. (The cornea is the clear outer surface of the eye, the “window” through which light must pass. Although there are conditions that cause whitening or clouding of the cornea, these aren’t cataracts.) The lens is located inside the eyeball, within a membranous “bag.” (Because it sits behind the iris, it’s not easily seen without special instruments, and without first dilating the pupil.) So even if your eye looks clear in the mirror, this doesn’t necessarily mean that you don’t have a cataract.

Types of Cataracts and Their Symptoms

The typical cataract that occurs with age is called a nuclear sclerotic cataract. The name refers to the center, or nucleus, of the lens. As the normal lens ages, the nucleus enlarges, and its protein structure starts to change. The lens gradually loses its clear appearance and becomes a yellowish or greenish color. Over time, as the nuclear cataract progresses, the lens can actually turn brown. (This is what eye doctors mean when we use words like clouding or haziness to describe cataracts.) People with nuclear sclerotic cataracts typically have trouble seeing at a distance. Many stop driving at night because of poor vision and because car headlights appear blurred. They also find that the quality and brightness of light becomes

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very important for seeing. They have trouble in dim light and must increase the wattage of light bulbs at home to help them read and get around the house better at night. They often read best in bright sunlight, unless glare becomes a problem; then, hazy days may bring more comfort and better vision.

Other developments also seen with cataracts may include cortical changes and posterior subcapsular lens changes. Cortical changes occur in the outer layer, or lens cortex; they’re the result of chemical imbalances that cause water to be drawn into the outer cortex. This excess water has an adverse effect on lens fibers—think of waterlogged carpet strands—causing a decrease in the clarity of the lens. (Interestingly, one of the dictionary’s definitions of cataract is “a waterfall or great downpour.”) Whitish, irregular lens areas and streaks caused by this flooding create problems with diffraction (how light is bent and focused; see chapter 4). People with cortical lens changes that fall within their visual axis often complain of monocular double vision (double vision or a “ghost” image seen when looking through only one eye). When double vision occurs with both eyes open, but not in either eye alone, it’s very rarely due to cataracts. (Double vision with both eyes open needs to be carefully evaluated by an eye doctor for eye muscle imbalances or other problems.)

These nuclear and cortical lens changes usually happen slowly, and at a different pace in each eye. Posterior subcapsular lens changes, on the other hand, can progress rapidly and tend to be much more advanced in one eye

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than the other. These are often known as fast cataracts. People with posterior subcapsular cataracts form an opaque, plaquelike cell growth on the back surface of the lens. This is different from the diffuse haziness of nuclear sclerotic cataracts or the focusing problems and distortion of cortical lens changes. This growth often occurs dead center in the lens, right in the path of central light rays that pass to the macula for reading vision. It can cause people to have more problems seeing close up than at a distance, and to experience a lot of discomfort from glare. People with diabetes, people taking oral steroids, and people who have suffered eye trauma or undergone previous eye surgery are more prone to develop these cataracts. But posterior subcapsular cataracts can also occur in young, healthy people who don’t have any of these risk factors. Because of their rapid onset and marked impairment of reading vision, these cataracts are often tremendously debilitating.

There are many other, rarer types of lens changes including cholesterol cataracts, “sunflower” cataracts, phenothiazine cataracts, and congenital lens changes. But nuclear sclerotic lens changes—alone or in combination with other lens changes—are overwhelmingly the most common.

Symptoms Not Typical of Cataracts

A hazard of automatically blaming cataracts for many eye problems is that making this assumption—without the medical diagnosis to back it up—often delays the diagnosis of other eye diseases until it’s too late for treat-

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What Symptoms Are Not Typical of Cataracts?

Symptoms unlikely to be associated with cataracts include:

•Eye discomfort

•Pain

•Redness

•Discharge

•Excess mucus

•Tearing

•Itching

•Irritation

•Aching in the eyeball

ment. As mentioned above, cataracts usually cause problems with vision; on the other hand, they do not typically cause eye discomfort or pain, or any change in the appearance of the eye or the production of tears.

Cataracts are also not a major cause of eye fatigue or tired eyes; as we get older, these symptoms are usually due to dry eyes or the need for new glasses or contacts. Also, a rapid deterioration in vision is usually not due to a cataract. (However, as always, there are a few exceptions to this rule, and a careful examination by an eye doctor is necessary to determine the true cause of deteriorating eyesight.) Likewise, cataracts usually aren’t to blame for a sudden loss of reading vision or lost side vision (two

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symptoms, by the way, that call for immediate professional attention!).

Who’s at Risk?

Among the risk factors associated with developing cataracts, age is by far the biggest. It’s important to note here that most cataract lens changes are simply part of the normal aging process; theoretically, all of us will eventually experience some degree of cataract if we live long enough. And again, although everybody has at least some cataract lens changes by age sixty-five, these usually aren’t commented upon by eye care specialists unless they appear to be affecting a patient’s vision or unless they can help explain symptoms such as glare, foggy vision, or difficulty with night driving. Many people, however, live their whole lives without ever having cataract problems that need treatment.

Cataracts have been found to be more common in women than men, in blacks than whites, and in people living in developing countries near the tropical belt than people living in the United States and Europe. Having diabetes, a strong family history of visually significant cataracts, or taking certain medications (in particular, corticosteroids) have also been shown to increase someone’s likelihood of developing cataracts. Smoking has also been shown to increase a person’s risk of developing nuclear, but not cortical, cataracts. The role of nutrition in cataract formation is not clear.

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