Glaucoma — "Thief of the Night" Glaucoma is the name for a group of diseases that can damage the optic nerve of the eye. Good vision depends on a healthy optic nerve, Dr. Nussenblatt explained. The eye has a mechanism much like a drain system: A clear fluid regularly flows in and out of the anterior chamber of the eye, nourishing nearby tissues, and keeping the pressure in the eye at whatever is normal for each person. However, in an eye affected with the most common form of glaucoma — called open angle glaucoma — the drain is clogged for some unknown reason and the fluid cannot flow out. This build-up of fluid in the anterior chamber causes the pressure to rise and can damage the optic nerve. The pressure must be lowered and controlled — either with eye drops, pills, or surgery — to prevent damage to the optic nerve and preserve vision. Glaucoma affects at least 2 million adults in the United States and is the leading cause of blindness here. As many as 1 million people here may have glaucoma and do not know they have it. Initially, people with glaucoma may begin to lose their peripheral, or side vision. "That's good in a way because the peripheral vision is what we use least and in the end it's something that potentially could be expendable," said Dr. Nussenblatt. However, that is also bad because the vision loss can progress very rapidly or very slowly without the person realizing it, until central vision has been markedly altered as well, he said. Because of its often "silent" progression, glaucoma is commonly called the "thief in the night." Your eye care provider can detect the first signs of glaucoma during a comprehensive eye examination, he said. Your pupils must be dilated (usually with a drop or two of medication) so the doctor can look into the back of your eyes. (See box for details about a comprehensive eye exam.) NEI is supporting many research studies to find better ways to detect, treat and prevent vision loss in people with glaucoma. Studies are also aimed at finding out more about who is likely to get glaucoma, when to treat people with increased pressure in their eyes, and which treatment to use first.

Cataract — Most Common Cause for Vision Loss Another eye disorder that can occur with little warning is a cataract, which is a clouding of the lens within the eye. The lens is composed of water and protein. The protein is arranged so that light can pass through and focus on the retina. If the protein clumps together, however, it starts to cloud over a small area of the lens. In time, this cloudy mass of protein — called a cataract — can grow larger, making it hard to see. That's when it becomes a problem. Like glaucoma, cataracts are painless. Often people with cataracts begin to complain about glare. "When these people have bright lights shined on them, their vision may drop rather dramatically," explained Dr. Nussenblatt. Colors may seem faded, and eyeglasses or contact lenses may need frequent changing. Ironically, people with cataracts may need increased light to read, and to lessen other vision problems. If the cataract worsens, however, surgery may be necessary to remove the cloudy lens and replace it with a new lens (see box for a list of lens substitutes.) By the year 2020, there will be more than 12 million individuals in the 65 or older age group who will probably need treatment for cataracts, he noted. Besides age, other factors that scientists believe may put you at greater risk for developing a cataract include heredity, alcohol use, smoking, long-term exposure to high levels of the sun's ultraviolet rays, some medications and systemic disorders such as diabetes. "Cataract is perhaps the most common cause for a drop in vision in the world, but it is reversible," Dr. Nussenblatt noted. "Cataract removal is the most common operation performed in the United States today. There are 1.5 million cataract operations done yearly; 95 percent of the people who have the surgery see well afterwards." Usually, a cataract needs to be removed only when it affects your vision so much that it interferes with your daily activities. NEI is conducting a nationwide clinical study called Age-Related Eye Disease Study. Scientists are examining, among other things, how cataracts develop and what factors put people at risk for developing them. The study is also looking at whether certain vitamins have any role in protecting the eye. Right now, there is no absolute evidence to support that idea. Other studies are looking at drugs that could slow down or delay cataract formation, as well as ways to improve surgical techniques.

Replacing a Lens After Cataract Surgery The lens of your eye is an important part of seeing clearly. It focuses light onto the retina. In cataract surgery, the affected lens is removed and, therefore usually needs to be replaced. Currently, there are three types of substitute lenses: an intraocular lens (IOL), a contact lens, or cataract glasses. About 90 percent of people who need to replace their lens choose an IOL. Of them, about 90 percent achieve 20/40 vision or better. Intraocular lens: An IOL is a clear, plastic lens that is placed in your eye during cataract surgery. It requires no care. With an IOL, you'll have better vision and won't feel or see the new lens. A few people cannot have an IOL because they're sensitive to the material the lens is made of, their eye structure isn't suitable, or they have certain other eye diseases. Contact lens: Most people who do not have an IOL wear soft contact lenses. Extended-wear lenses are helpful if you have trouble putting in and taking out contacts. Your eye care professional can remove and clean the lenses for you periodically. As with all contact lenses, it is important to follow instructions about proper use and care. Cataract glasses: People who don't want to use contact lenses or whose eyes are too sensitive to wear them may choose cataract glasses. Cataract glasses affect vision differently than regular eyeglasses. Their powerful magnification (20-35 percent) may make it harder for you to judge distance and may distort your side vision. Until you've adjusted to these changes, you will need to be careful when you drive or do other activities.

Age-Related Macular Degeneration Takes Centerstage In stark contrast to glaucoma and cataract, age-related macular degeneration (AMD) diminishes sight in a dramatic way: It affects the central vision. Although people with AMD rarely go blind because of it, many find it difficult to read, drive and perform other daily functions that require central vision. The number of cases of the disorder increases substantially among individuals over age 60. "About 5 percent of the 34 million adults over age 65 — or 1.7 million of us — have some degree of vision loss because of this disease," said Dr. Nussenblatt. "AMD causes marked alterations that affect, almost in a diabolic way, our ability to see. The rest of the eye can be totally normal. AMD is the leading cause of irreversible vision loss in the United States." The macula is located in the center of the retina, which is the light-sensitive layer of tissue at the back of the eye. Normally, when you are reading, light is focused onto the macula. AMD can affect this in two ways. When the light-sensitive cells in the macula break down slowly over time, less macula is available to handle light properly. This breakdown is called dry AMD, which affects about 90 percent of people with AMD. Although dry AMD cannot be treated, most people do not lose their vision entirely from this form of the disorder, because the damage to the macula occurs so slowly. In wet AMD, new blood vessels begin to develop behind the retina. These new vessels tend to be very fragile and often become leaky. The blood and other fluid they leak causes rapid deterioration of the macula. Although only 10 percent of people with AMD have this form, wet AMD accounts for 90 percent of all blindness from AMD. People with dry AMD will probably not notice any changes in their vision. Over time, a blind spot may begin to develop in their central vision. People with wet AMD, however, may begin to see the blind spot quickly. In addition, wet AMD can cause straight lines to appear wavy. During your eye exam, your eye care professional may give you a special grid to stare at; how this grid looks to you may help the doctor to diagnose AMD. Also, your doctor will look for yellow deposits called drusen in the retina. The presence of drusen is an early sign of AMD. Dry AMD cannot be treated, but because it develops so slowly, most people affected live normal, active lives. A small number of people with wet AMD can be treated with laser surgery. The laser is used to seal the leaky blood vessels and can be of some value in stopping further vision loss. NEI scientists are looking into genetic factors that may be involved in the disease and last year identified one of the genes involved in AMD. The ARED study is also trying to identify factors that make people more likely to develop AMD.

Diabetic Retinopathy — Timely Treatment Is Key The final major age-related eye disease whose symptoms are often ignored is diabetic retinopathy. This potentially blinding disorder is a complication of diabetes. Diabetes causes abnormal changes in the blood vessels throughout the body, including the retina. In diabetic retinopathy, the macula is spared, Dr. Nussenblatt explained. "However, these blood vessels can also become leaky and begin to grow where they should not. Sometimes these new vessels, which are very brittle and fragile, tend to break and bleed, or hemorrhage." The hemorrhaging taints the eye's normal gel, which should remain clear, he said. With healing, these blood vessels will contract and detach the retina. About 16 million Americans have diabetes and nearly 25,000 new cases of blindness occur annually because of diabetes. Fortunately, laser surgery for diabetic retinopathy has dramatically improved the chances of saving a person's vision. In 1970, a person with diabetic retinopathy had a 50 percent chance of being blind in 5 years. Today, there is less than a 5 percent chance of this occurring — a 10-fold decrease in this problem. What is important for people with diabetes is to control blood sugar levels and to have regular eye exams, Dr. Nussenblatt stressed. "An NIH study showed that better control of blood sugar levels will slow the onset and progression of retinopathy and therefore will lessen the need for laser surgery. These are the things individuals can actively do to keep their sight." NEI is studying new drugs that may be able to stop the early loss of the cells in the walls of the retina's blood vessels. Other studies are looking at ways to turn off the enzymes that stimulate the growth of new blood vessels in the retina. Dr. Nussenblatt said the take-home message for preventing, or lessening the impact of all four age-related eye diseases is basically the same: Have regular comprehensive eye exams so you and your doctor can detect and treat problems early. Because symptoms for these AREDs are often "silent" or ignored, periodic eye exams may be the only way to save your sight. — a report from The NIH Word on Health, January 1999 The National Eye Institute is currently conducting the Age-Related Eye Disease Study (AREDS) of age-related macular degeneration and cataract. To find out how you can participate in the study, contact: The Patient Recruitment and Referral Center Warren Grant Magnuson Clinical Center, National Institutes of Health Bethesda, Maryland 20892-4754 Phone: 1-800-411-1222 Fax: 301-480-9793 E-mail: prrc@nih.gov For more information about age-related eye disease, contact: National Eye Institute Office of Health Education and Communication 9000 Rockville Pike Building 31, Room 6A32 Bethesda, MD 20892 Phone: 301-496-5248 or visit NEI's website at http://www.nei.nih.gov/ For more information about this article, reporters may contact: Carla R. Garnett Writer and Editor, NIH Phone: 301-496-2125 Fax: 301-402-1485 E-mail: cg9s@nih.gov