With a focus on giving those diagnosed with macular degeneration the necessary information to make sound treatment choices, this reference aims to answer patients' questions and ease their anxiety. The book provides information on the symptoms, causes, and emotional impact of macular degeneration; how the disease is diagnosed; choosing the right physician; and how to adapt the home and workplace to be “eye friendly.” In addition, it outlines the newest treatment options, drugs and surgical techniques, ways to slow the progression of the disease, and the importance of nutrition and general fitness on eye health. Written by two doctors with decades of experience treating thousands of patients, it supplies essential facts while affirming that people living with the disease can still enjoy a normal, happy life.
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A Patient's Guide to Treatment
By David S. Boyer, Homayoun Tabandeh, Jack Kusler
Addicus Books, Inc.Copyright © 2012 David S. Boyer, M.D., and Homayoun Tabandeh, M.D.
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Macular Degeneration: An Overview
Macular degeneration is a condition that causes deterioration of the macula, a small section of the retina that is responsible for sharp, central vision. With this condition, central vision deteriorates. It is estimated that as many as 11 million people in the United States have some form of macular degeneration, which is also known as agerelated macular degeneration (AMD). In the United States, macular degeneration is the most common cause of vision loss in people over age fifty. In people under age fifty, there is only a 2 percent chance of developing macular degeneration. But by the time a person reaches age seventy-five, that risk jumps to nearly 30 percent. With our aging population, the number of people with macular degeneration is expected to skyrocket in the coming decades. In fact, it is estimated that by 2050, up to 22 million people will suffer from macular degeneration.
How the Human Eye Works
To fully understand macular degeneration and how it develops, it is a good idea to first look at how the human eye works. One of the easiest ways to understand the inner workings of the eye is to think of it as a camera.
The cornea is the clear, dome-shaped front part of the eye that works with the lens of the eye to act as the camera's lens, or focusing system. The retina, a very thin layer of light-sensitive tissue lining the inside of the back of the eye, is the film. In order to provide clear, distortion-free pictures, the film in a camera — or in this case, the retina — must be completely flat. If the film — or the retina — is damaged in any way or has any irregularities, the images will not be crystal clear; there may be distortion, blurring, or other problems.
Parts of the retina and surrounding tissues include the following:
Macula: The macula is the center part of the retina and is critical for central vision, which is used to perform activities that require seeing fine detail, such as reading, watching television, driving, and recognizing faces at a distance. The macula is also what allows us to see our world in color.
Fovea: At the center of the macula is a tiny dimple known as the fovea. The most sensitive portion of the macula, the fovea is responsible for our sharpest vision.
Choroid: In a healthy eye, the retina lies over a flat carpet of blood vessels called the choroid. The choroid supplies the retina with nourishment.
Retinal pigment epithelium: A single layer of very specialized cells called the retinal pigment epithelium (RPE) buffers the retina from the choroid.
Bruch's membrane: Lying between the RPE and the choroid is a thin, semipermeable membrane called Bruch's membrane, which serves as an additional protective buffer between the retina and the choroid.
Nutrients traveling from the choroid blood vessels to the retina must pass through Bruch's membrane and then through the retinal pigment epithelium. On the other hand, waste products generated by the retina must pass through the retinal pigment epithelium and then through Bruch's membrane in order to be transported away by the blood vessels in the choroid. This inflow of nutrients and outflow of waste products, or debris, occurs twenty-four hours a day to keep the retina healthy.
As the Eye Ages
With aging, Bruch's membrane tends to thicken, disturbing the delicate balance of nutrients and debris. The flow of nutrients slows, and debris may begin to accumulate within the fibers of Bruch's membrane. The debris can form into small, yellow mounds called drusen. It is believed that all people will accumulate some debris in Bruch's membrane during their lifetime, but only some will develop drusen. The thickening of Bruch's membrane and the accumulation of drusen contribute to the development of macular degeneration. Other conditions associated with the development of the disease include degenerative changes in the retinal pigment epithelium, in the blood vessels in the choroid, and in the light-sensitive photoreceptors in the retina. Photoreceptors are retinal cells which detect light and enable us to see.
Types of Macular Degeneration
There are two basic types of macular degeneration: dry macular degeneration and wet macular degeneration. Dry macular degeneration is the most common form, affecting up to 90 percent of people with macular degeneration. There are three stages of dry macular degeneration: early, intermediate, and advanced. Dry macular degeneration can develop into wet macular degeneration, which is considered to be the advanced form of the disease. However, only about 10 percent of patients with mild dry macular degeneration will develop the wet form of the disease. Patients with severe, or high-risk, dry macular degeneration have a 30 to 50 percent chance of developing wet macular degeneration within five years of their initial diagnosis.
Dry Macular Degeneration
Dry macular degeneration is a chronic condition that affects the macula. It can lead to vision problems, such as blurring or blank spots, in the central field of vision.
Dry macular degeneration is characterized by a number of changes in the eye. One of the most common early changes is the accumulation of drusen, or small mounds of debris, in the membrane below the retina, Bruch's membrane. Other changes include the gradual breakdown of the tissues below the retina and the light-sensitive cells in the retina. Dry macular degeneration may also cause the degeneration of the small blood vessels in the choroid below the retina. In some cases, these changes are mild and may not produce any noticeable symptoms. In other cases, the changes are more pronounced and may lead to problems with vision.
In more-severe cases of dry macular degeneration, the loss of tissues and blood vessels may occur around the macula in a patchy pattern. This is called geographic atrophy and represents a more advanced form of dry macular degeneration. With this form, central vision problems may be mild, moderate, or severe, but tend to evolve gradually.
Wet Macular Degeneration
Wet macular degeneration occurs when abnormal blood vessels grow under the retina. These blood vessels originate from the small blood vessels in the choroid under the retina. This process is called choroidal neovascularization (CNV). Unlike healthy blood vessels, these abnormal blood vessels are fragile, causing them to leak blood or other fluids under the retina. Leakage builds up under the retina, damaging it and causing the macula to bulge or lift away from the retina, resulting in an uneven surface. Remember, like the film in a camera, the retina must be flat in order to produce clear images. When it takes on an irregular shape, images become distorted and blurred. In addition, when blood or other fluids build up under the retina, the retina's light-detecting photoreceptors become damaged and cannot function normally.
With wet macular degeneration, these changes can occur very suddenly and may result in dramatic visual impairment. Although wet macular degeneration affects only about 10 percent of all people with macular degeneration, it accounts for more than twothirds of significant vision loss among people with macular degeneration.
In wet macular degeneration, the choroidal neovascularization, or CNV, is subclassified into three types: classic, occult, or a mix of the two.
Classic wet macular degeneration occurs when abnormal blood vessels (resulting from CNV) rapidly leak blood or other fluids into the tissues under the retina, potentially causing sudden and significant problems with central vision.
Occult wet macular degeneration is associated with less-pronounced leakage of blood or other fluids into the tissues under the retina. This has a less dramatic impact on the shape of the macula and produces less-severe visual impairment initially. Although vision problems also occur at a slower pace with this type, occult wet macular degeneration can eventually cause major macular bleeding and loss of central vision.
Combination of Classic and Occult
The third type of wet macular degeneration is basically a combination of the classic and the occult types. With this combination type, there may be rapid leakage in some parts of the eye and less-pronounced leakage in other areas of the eye.
Approximately 90 percent of all cases of wet macular degeneration are predominantly occult or a combination of classic and occult. With the new treatments for wet macular degeneration, the distinction between the classic and the occult forms of the condition has become less important, as both types respond well to the treatments.
Retinal Pigment Epithelial Detachment
Retinal pigment epithelial detachment (PED) is a condition in which fluid builds up behind the thin layer of tissues under the retina, causing a small "blister" to develop under the macula. In wet macular degeneration, this condition occurs because of the growth of abnormal blood vessels under the retinal pigment epithelium. It is thought that people who have this condition may have a slower response to treatment for wet macular degeneration. Apart from wet macular degeneration, many other retina and choroid conditions can cause retinal pigment epithelial detachment.
In wet macular degeneration, macular scarring occurs as a result of leakage of blood or other fluids under the macula. The scarring permanently damages the overlying retina and causes reduced vision. The aim of treatment for wet macular degeneration is to stabilize the fragile abnormal blood vessels so that macular scarring is prevented or minimized. The smaller the area of scarring, the better the final vision.
Severe macular scarring, also called disciform scarring, is the end stage of wet macular degeneration. By this stage, central vision may be severely affected, depending on the location of the scar tissue relative to the fovea (the center of the macula). Currently, there are no effective treatments for macular scarring.
Other Effects of Wet Macular Degeneration
An uncommon effect of wet macular degeneration is bleeding that invades the vitreous, the clear, jellylike substance that fills the inside of the eye. This type of bleeding is called a vitreous hemorrhage, and it can cause sudden impairment of both central vision and peripheral vision, which is the ability to see objects and movement outside the direct line of vision. Fortunately, with treatment, peripheral vision may be restored. Without treatment, vision loss can be permanent.
Visual hallucinations may occur in individuals who have moderate to severe vision loss in both eyes. These hallucinations may be simple patterns, colors, or lights, or may include formed and vivid visual images. The condition of visual hallucinations associated with poor vision is called Charles Bonnet syndrome. The syndrome is named after the Swiss naturalist and philosopher Charles Bonnet, who described the condition in the eighteenth century. Bonnet first documented the condition in his eighty-nine-year-old grandfather, who was blind from cataracts in both eyes but perceived images of men, women, birds, carriages, buildings, and tapestries.
Although Charles Bonnet syndrome occurs commonly in people with wet macular degeneration and poor vision, it is underdiagnosed. Characteristics of the syndrome include hallucinations in which the characters or objects are smaller than normal and often fit into the person's surroundings. The hallucinations are only visual and do not involve any other senses. The hallucinations may last only a few seconds or continue for hours. They occur more frequently in dim or dark lighting, such as in the evening. People who have this condition understand that the hallucinations are not real.
It is estimated that 10 to 40 percent of adults over age sixty-five with significant vision loss experience Charles Bonnet syndrome. However, many affected individuals may be reluctant to report the symptoms to their family members or doctors, out of fear that they will be labeled insane.
There is no treatment of proven effectiveness for this condition. It usually disappears within two years, although periodic relapses may occur. For those experiencing visual hallucinations, awareness that this is a known and common phenomenon, and not a mental illness, can alleviate distress and improve their ability to cope with the hallucinations. There are also a few activities that may help stop hallucinations, such as increasing the surrounding lighting or interrupting vision for a short time by closing the eyes or blinking. In some severe cases, medications such as selective serotonin reuptake inhibitors may be helpful.
Risk Factors for Macular Degeneration
It is not known exactly why some people develop macular degeneration and others do not, but it is thought that certain physical traits and lifestyle factors make some individuals more vulnerable to the disease. These are called risk factors. The more risk factors you have, the greater your chance of developing this condition. Many risk factors also tend to speed up the progression of macular degeneration. That's why it's important to understand and control the risk factors for this disease. By doing so, you can reduce your risk of developing macular degeneration or of the disease progressing.
Age is the greatest risk factor for macular degeneration. It is uncommon to develop macular degeneration prior to age fifty. After that age, however, the risk begins to increase and continues to rise as your age advances. By the time an individual reaches age seventy-five, he or she has a 30 percent chance of developing macular degeneration. Because age is the most significant risk factor, it is important that all individuals over age fifty self-test their eyes on a regular basis for signs of macular degeneration and visit an eye care professional at least once a year.
Macular degeneration occurs in all races but is more common in Caucasians than in nonwhites. However, scientists are now reporting that Asians may develop macular degeneration at nearly the same rate as Caucasians, who are more likely than African-Americans to experience vision loss from macular degeneration.
Women appear to be more likely to develop macular degeneration than men and, because they tend to live longer than men, are also more apt to experience vision loss. This does not mean that men do not need to be concerned about macular degeneration. Regardless of gender, everyone over age fifty should regularly self-test for signs of macular degeneration.
Mounting evidence suggests that a person's genes may play a role in the risk for this eye condition. A family history of macular degeneration is present in nearly three out of four cases of macular degeneration, according to research. Scientists believe that several genes may be associated with increased risk.
If any of your immediate family members has macular degeneration, your chance of developing it is two to three times greater than for people whose immediate family members do not have the disease. If one (or more) of your first-degree relatives has advanced macular degeneration, you have a 50 percent chance of developing it, as well.
Current smokers are at greater risk for the disease and are more likely to develop advanced macular degeneration than nonsmokers. Quitting smoking is one of the best measures an individual can take to decrease the risk for this vision-threatening condition. Within the first year of quitting smoking, the chance of developing macular degeneration is reduced. The longer a person remains smoke-free, the lower the risk.
Excerpted from Macular Degeneration by David S. Boyer, Homayoun Tabandeh, Jack Kusler. Copyright © 2012 David S. Boyer, M.D., and Homayoun Tabandeh, M.D.. 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.
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Table of Contents
1 Macular Degeneration: An Overview,
2 Symptoms and Signs of Macular Degeneration,
3 Getting a Diagnosis,
4 Treatments for Macular Degeneration,
5 Reducing the Risk of Macular Degeneration Progression,
6 Living with Macular Degeneration,
About the Authors,