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SUNDAY, July 27, 2003 (HealthDayNews) -- Perfect vision may be more of a blessing than most people realize.
As folks age, the chances become greater that they'll start to lose vision to one of four diseases: diabetic retinopathy, macular degeneration, cataracts or glaucoma.
Blindness affects more than 1 million Americans age 40 and older, according to a 2002 report conducted jointly by the National Eye Institute and the group Prevent Blindness America. Another 2.4 million older Americans suffer from some sort of visual impairment. The prevalence of blindness and vision impairment increases rapidly in the later years, particularly after age 75.
Of the four major vision-robbing diseases, however, only diabetic retinopathy -- a common complication of diabetes -- affects large numbers of both young and old people.
That's because of the prevalence of diabetes in the United States, says Betsy van Die, spokeswoman for Prevent Blindness America, a national volunteer eye health and safety organization. The U.S. Centers for Disease Control and Prevention estimates that 10.3 million Americans have diagnosed diabetes, while an additional 5.4 million have diabetes but have not been diagnosed.
Diabetic retinopathy affects the tiny blood vessels of the retina, says Dr. Richard Bensinger, a Seattle ophthalmologist and spokesman for the American Academy of Ophthalmology.
"If diabetes is not well-managed, one of the things that can happen is the blood vessels in the retina start to leak," he says. The leaking can lead to scar tissue on the eye and, in severe cases, the retina can become detached. Serious damage also can occur when abnormal new blood vessels grow on the surface of the retina.
Diabetic retinopathy can affect almost anyone with diabetes, although those who've had diabetes for a long time are at greater risk. The only way to stave off vision loss, van Die says, is to scrupulously treat the diabetes, closely watching blood sugar levels and blood pressure. Experts advise people who have diabetes to see an eye doctor at least once a year.
The most prevalent vision disease of older Americans is cataracts, affecting nearly 20.5 million people age 40 and older, or about one in every six people in that age range, according to the 2002 vision report.
More than half of all Americans will develop cataracts by the time they're 80.
But cataracts also may be the most treatable eye disease. The clouded natural lens can be removed surgically and replaced with an artificial implant. The success rate for cataract surgery currently stands at 95 percent, the report says, with more than a million such surgeries conducted each year.
"Surgical responses to cataracts are fabulous," Bensinger says. "The results are one of the most predictable and safe operations you can have."
Cataracts involve a loss of transparency in the eye's naturally clear lens, resulting in a cloud over the lens. The cause of cataracts is unclear, but van Die says they may result from lifetime exposure to the ultraviolet radiation contained in sunlight. People who've sustained eye injuries also face a greater risk of contracting cataracts. And, researchers believe that other lifestyle factors might affect cataract development, including such things as cigarette smoking, diet and alcohol consumption.
Glaucoma is considered the most insidious of the four diseases. It causes gradual degeneration of the optic nerve, which carries visual information from the eye to the brain.
With glaucoma, vision is slowly lost -- so slowly that it often is not noticed until a significant amount of nerve damage has occurred. As many as half of all people with glaucoma may be unaware of their disease, according to the vision report.
"Early detection is key," van Die says. "Once you've lost any vision to glaucoma, it's gone permanently. It's called the 'sneak thief of sight' because of that."
Glaucoma affects more than 2.2 million Americans age 40 and older. The risk of contracting it increases for people who have ever had eye surgery or an eye injury, have used steroids for an extended period of time, are very near-sighted or suffer from diabetes. Race also is a factor, with a greater percentage of African-Americans and Hispanics contracting the disease. People with any of these risk factors should see an eye doctor every year, experts say.
Treatments do exist, however, to slow or halt vision loss caused by glaucoma, van Die says. Medications, laser treatments and surgery have been shown to help sufferers.
The fourth major eye disease -- age-related macular degeneration -- is believed to be the most common cause of blindness among older Americans, according to the vision report. That's because the disease often damages central vision.
Macular degeneration primarily affects the part of the retina responsible for sharp central vision. "You can still have peripheral vision, but your central vision fades over time," van Die says.
One type of macular degeneration involves the presence of fatty deposits under the light-sensing cells in the retina. The other type involves the growth of tiny new blood vessels under the retina that leak fluid or break open.
More than 1.6 million Americans age 50 and older have late-stage macular degeneration, yet there is no known cause or agreed-upon therapy for the disease.
"The treatment for it is just not there, [and] we don't know why it happens," Bensinger says. "It's really a frustrating, vexing thing."
That also means that clear risk factors for macular degeneration are unknown. The best advice, van Die says, is for people to generally live a healthy lifestyle.
But hope is growing that some sort of treatment will be found. Van Die cites a 2001 study by the National Eye Institute that found a combination of vitamin supplements and zinc can slow the progress of macular degeneration in people suffering from moderate or advanced cases.
More information
To learn more about a range of vision problems, visit the Webs site of Prevent Blindness America or the National Eye Institute.
