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A Guide to Treatment
By Paul E. Garland, Bret L. Fisher
Addicus Books, Inc.Copyright © 2015 Addicus Books, Inc.
All rights reserved.
Cataracts: An Overview
Age-related cataracts are common. Most of us will develop them as we grow older. The American Academy of Ophthalmology suggests that by age seventy-five, 70 percent of adult Americans will experience the blurring and distorted vision associated with cataracts. Statistics suggest that by the year 2020, cataracts will affect more than 30 million Americans, a considerably higher number than the 20 million adults affected today.
But what exactly is a cataract? What are the symptoms? And what puts you at risk for developing them? It's important that you pay attention to cataracts once they start developing because they can gradually, but significantly, reduce your vision and even cause blindness. The good news is that, thanks to modern medicine, cataracts are very treatable, and impaired vision can be restored.
What Is a Cataract?
The term cataract has ancient roots in the Greek and Latin terms for "waterfall." That's because centuries ago people believed the clouding in their eyes actually came from an opaque material flowing like water over their eyes. Indeed, a cataract is a clouding of the eye lens. As the cloudiness increases, the cataract can blur or distort your vision and cause colors to fade. If not treated, cataracts can lead to blindness. Most cataracts are related to normal aging, but they also can result from other issues such as trauma, sun exposure, or diseases. To understand how any cataract forms, it's helpful to understand the makeup of the lens of your eyeball. The lens is made up mostly of protein and water. The protein is arranged in such a way that when light passes through it to get to the retina, it does so without distortion.
As people age, however, changes in the eye cause protein to break down and clump together, creating a buildup that hardens and blurs your vision. More specifically, the lens thickens, becoming less flexible and transparent. At first, the clouding involves a small area, but over time it increases in size, density, and color, eventually engulfing the entire lens. Your vision is affected because the clumping scatters light coming through the lens in such a way that a sharply defined image can't reach the retina. Your lens no longer has the ability to adjust appropriately to see up close or far away. Instead, everything you see is faded, distorted, or blurred.
The human eye works much like a camera. In a camera, an image passes through the lens and strikes the film, where it is imprinted into the film. In the eye, an image passes through the lens onto the retina. The image message travels through the optic nerve to the brain, where it is "interpreted."
Types of Cataracts
Eye surgeons have different ways of classifying cataracts based on their location within the lens. The three basic types are nuclear, cortical, and subcapsular, as explained in the text that follows.
Other types of cataracts, which are not caused by aging, are named according to their underlying origin. For example, these include congenital and traumatic cataracts.
Nuclear cataracts are the most common type of cataract. They form in the center, or nucleus, of the eye. They can start forming when you're only in your forties or fifties, but they usually don't significantly affect vision until you're in your sixties and seventies. In fact, by age seventy most men and women have some degree of clouding. Nuclear sclerotic cataracts cause yellow tinting that can eventually harden into a dense yellow or brownish yellow center. Vision gradually deteriorates with symptoms ranging from blurring and seeing halos around objects to having difficulty in distinguishing color or contrasts.
Cortical cataracts develop along the edge (cortex ) of the lens. They begin as streaks of whitish, wedge-shaped growths that eventually extend, like the spokes of a wheel, from the edge into the center of the lens. Because of this pattern, light tends to scatter when it hits the lens, causing initial problems with glare. Although older adults can develop cortical cataracts, they're a common problem in diabetics of all ages.
Posterior Subcapsular Cataracts
Posterior subcapsular cataracts form at the back of the lens, directly below the pocket or membrane that surrounds the lens. These cataracts begin as small cloudy areas blocking the path of light to the retina, causing light to scatter rather than remain focused. Symptoms include trouble seeing close-up for reading and sensitivity to bright light, causing severe glare. These cataracts tend to develop relatively quickly, in months rather than years. Although posterior subcapsular cataracts can be related to aging, they're more commonly associated with diabetes and prolonged use of prednisone or other prescription steroids. And, they tend to be seen in younger patients.
A nuclear cataract is the most common type of cataract. It can cloud the entire lens
A cortical cataract forms as a wedge on the lens and gradually extends "spokes" toward the center of the lens.
A subcapsular cataract forms toward the back of the lens and interferes with incoming light.
Unlike cataracts that develop as part of aging, congenital cataracts are present at birth. Although they can be associated with another medical condition, such as Down's syndrome, they also may be caused by genetics or a mother's health during pregnancy. If a woman experiences an infection such as German measles, for instance, her baby may be at risk for congenital cataracts. Cataracts that develop later in childhood are sometimes referred to as pediatric cataracts. Although they may be tied to other health conditions, they also can be caused by traumatic injuries to the eye. Damage can take months to years to develop. Congenital and pediatric cataracts are relatively rare. They occur in approximately 3 out of 10,000 children.
Traumatic cataracts are cataracts that result from traumas to the eye such as a blunt force, a penetrating injury, or exposure to certain chemicals. They can develop immediately or years later. The cataract forms at the site of the injury, which may involve the entire lens. As noted earlier, traumatic events to the eye are often the source of pediatric cataracts.
Immature and Mature Cataracts
Although most cataracts develop gradually, some individuals may experience rapid growth, particularly if several areas of the lens are affected. In either case, a cataract's natural progression from immature to mature is such that at first the clouding is not visible to the naked eye. You likely won't have noticed it because you aren't having any problems with your vision. The only way your eye doctor knows the cataract is forming is through a comprehensive eye examination.
As time passes, cataracts can advance to a more mature stage when they may be apparent to the naked eye. The cataracts may make the pupil appear milky white or totally opaque. At this stage, the cataract is sometimes referred to as a mature white cataract. At one time, ophthalmologists advised patients to delay surgery until the cataract was "ripe," but today they intervene relatively early to preserve a patient's vision.
Mature Brown Cataracts
Mature brown cataracts have progressed to the point of becoming hardened. Eye doctors often see them in older patients who haven't visited an eye doctor in many years. Over time, the protein clumps that form the cataract become very cloudy and are tinged a deep brown, which can affect the ability to distinguish colors. Mature brown cataracts also are often so dense at the center that removing them safely can be challenging. Routine eye examinations can eliminate the development of such advanced cataracts.
A cataract may cause no visual disturbances at first because the clouding affects only a small part of the lens, but as it grows, scattering even more light trying to reach the retina, a variety of symptoms occur. You may notice:
painless clouding, blurring, and dimming of vision
difficulty seeing at night or in reduced light
sensitivity to light and glare
presence of "halos" and glare from the sun or oncoming headlights at night
faded and yellow colors
need for brighter light for reading and other closeup activities
frequent changes in either eyeglass or contact lens prescriptions
double vision within one eye
Although there's no specific order to these early symptoms, eventually they'll interfere with your vision. People often describe the experience as looking through a frosty or fogged-over window. Others say their vision is like viewing the muted images of an impressionist painting. The effects make it difficult to see distant objects, identify facial expressions, and recognize color intensity. The impaired vision also affects one's ability to carry out activities of daily living, including driving. Although cataracts cause visual difficulties, they don't cause discomfort such as itching, burning, or aching, unless they become quite large.
At first, cataract-related symptoms can be treated with stronger lighting and up-to-date eyeglass prescriptions. But eventually, the only way to restore impaired vision is with surgery to remove the cloudy lens and replace it.
How Cataracts Develop
Cataract development or progression varies widely. Your ophthalmologist cannot predict with accuracy when you'll need surgery because cataracts develop at varying rates. In the early stages of a nuclear sclerotic cataract, for instance, the progress can be so slow that you're not even aware that your vision is affected. Sometimes patients become so adept at adapting to their diminished vision that they're surprised after surgery just how well they can see.
In most cases, cataracts don't harm other parts of the eye. (In a small percentage of patients, however, enlarged cataracts can increase the fluid pressure in the eye, causing damage to the optic nerve.) Cataracts also don't "spread" from one eye to the other, even though most people eventually develop them in both eyes. Even though you may get cataracts in both eyes, they don't necessarily occur in the same way in each eye — one cataract develops slower or more quickly than the other one.
Cataract Causes and Risk Factors
As noted earlier, advancing age is the primary risk factor for cataracts. Yet other issues can also increase the likelihood of developing cataracts, even in younger people. Although researchers still don't know why the lens of the eye changes as you get older, they've identified several medical and lifestyle factors that seem to hasten cataract development.
High blood pressure and obesity may increase your risk for cataracts, but diabetes is the most common chronic illness associated with non-age- related or early cataracts. Failing to keep your blood sugar controlled can trigger biochemical changes in the lens that accelerate the formation of a cataract. Diabetic retinopathy, a serious complication, can also impact your cataract and its treatment.
Prolonged corticosteroid or steroid use. Although oral and inhaled prescription steroids are successful treatments for conditions such as asthma, ulcerative colitis, and other chronic conditions, long-term use of these drugs can lead to cataracts sooner rather than later. Other medications such as cholesterol-lowering medications and anti-seizure medications can also be a trigger for long term growth of cataracts. If you've been taking any drug, particularly prednisone or similar steroid medications, you should see your eye doctor regularly.
Eye issues/injuries. Any number of eye problems can increase your risk of developing cataracts. Glaucoma and its treatment, including eye drops and surgery, pose a high risk for cataracts. Penetrating and blunt- force injuries, previous surgeries, and other eye conditions also can cause cataract formation, even years after the event. Furthermore, if you're extremely nearsighted or farsighted, your ophthalmologist will want to monitor you closely because both these vision problems can lead to early cataracts.
Studies repeatedly confirm that tobacco plays a prominent role in the development of cataracts. When cigarette smoke enters the body it enhances production of chemical particles called oxidants or oxygen-free radicals, which damage cells throughout the body, including those in the eye. Overproduction of these microscopic by- products causes lens proteins to clump into a cataract much earlier and quicker in smokers compared to non-smokers. Researchers continue to focus on the major role of oxidants in the development of cataracts.
Heredity plays a lesser role in the risk factors for the development of cataracts. Yet certain diseases that run in families can increase a person's susceptibility for cataracts. For example, cataracts are a common complication for those with retinitis pigmentosa, a disorder that damages the cells (called rods) in the retina that control night vision. Heredity may also be a factor in congenital or pediatric cataracts, which usually involve abnormalities in the shape or structure of the lens and surrounding membrane that lead to the clouding. Scientists are investigating possible causes of both adult and congenital cataracts. As for ethnicity and race, data suggests that some groups, such as African Americans, experience a higher rate of cataracts. But this is likely related to the higher rates of certain diseases, such as diabetes, in these populations, which already creates an increased risk of developing cataracts.
Because doctors don't have answers to all questions about how cataracts develop, they also don't have specific ways to stop them from forming. There are strategies, however, that may help you prevent or slow the formation of cataracts. You can't reverse the aging process, but you can take practical steps to protect your eyes from cataracts and other eye diseases.
Managing Your Health Issues
If you have a chronic condition that may increase your risk of cataracts, you need to manage it carefully. Researchers know, for instance, that uncontrolled blood glucose or sugar levels connected to diabetes can lead to biochemical changes in the lens that trigger several types of cataracts. Monitoring all of your health issues, particularly a chronic illness, may reduce your risk.
Studies have shown that smokers double their risk of developing cataracts over nonsmokers. The more heavily they smoke, the greater the susceptibility. There are many health reasons to quit smoking, and protecting your eyes against early and severe cataracts is an especially important one. Determining which smoking cessation method works best for you — medication, counseling, or classes — can be helpful.
Protect Your Eyes from the Sun
The ultraviolet rays emitted by the sun have destructive properties that can promote cataracts. Penetrating the outer layers of the skin, ultraviolet-B (UVB), in particular, is believed to cause changes in the lens that eventually lead to clouding. Deeper ultraviolet-A (UVA) rays promote the release of damaging oxygen-free radicals, which also play a role. Wearing sunglasses every time you're outside can be effective in blocking damaging rays.
Scientists have yet to prove conclusively how a diet rich in vitamins and minerals might be linked to avoiding cataracts. But evidence suggests that eating a variety of fruits and vegetables every day provides many of the antioxidants and other nutrients necessary to maintain healthy eyes. One British study, called the EPIC-Oxford Cohort, even suggests a significant decrease in cataract risk among some of the 65,000 participants, including 27,640 individuals older than age forty. Of this group, vegetarians, fish eaters, and vegans experienced drops of 30 percent, 21 percent, and 40 percent respectively in their risk for cataracts. Among meat eaters, the more ounces they consumed per day, the higher their cataract risk. Further research is needed on the exact role diet plays in preventing or slowing cataracts. But foods rich in vitamins and minerals likely will help you maintain good eye health.
Schedule Regular Eye Examinations
Comprehensive eye examinations can detect eye diseases, including cataracts, at their earliest stages. Even though age-related cataracts develop over years, undergoing routine exams helps your doctor keep track of their progress so they can be addressed when they start causing vision problems. Your eye care professional will suggest an appropriate schedule for you, which will likely include yearly exams if you are older.
Excerpted from Cataract Surgery by Paul E. Garland, Bret L. Fisher. Copyright © 2015 Addicus Books, Inc.. Excerpted by permission of Addicus Books, Inc..
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
1 Cataracts: An Overview,
2 Getting a Diagnosis,
3 Your Intraocular Lens,
4 Planning for Cataract Surgery,
5 Undergoing Cataract Surgery,
6 Recovering from Cataract Surgery,
7 Special Conditions and Cataract Surgery,
About the Authors,