VISION DISORDERS: UNDERSTANDING EYE DISEASES AND CONDITIONS
A serious look at glaucoma, macular degeneration and more
BY:MARY ELIZABETH TERZELLA
Many of us fear blindness more than any other condition except cancer—with good reason. By age 65, one in three Americans has some form of vision-threatening eye disease. Fortunately, regular eye exams and an evolving array of treatments can help prevent, reverse or control the four most common causes of blindness.
Cataracts
Thanks to cataract surgery, people don't have to suffer blurry vision. About half of Americans ages 65 to 74, and 70 percent of those older, have cataracts, a clouding of the lens of the eye. In most cases, normal aging and a lifetime of sun exposure cause proteins in the eye to break down and clump together, reducing the sharpness of the image that reaches the retina.
At first, cataracts do not cause any loss of sight. Over time, however, they often increase in size, making images seem fuzzy. As with other potentially blinding eye disorders, complaints of blurry vision or difficulty reading or seeing the TV may be signs of worsening cataracts, says Robert Cykiert, MD, professor of ophthalmology at New York University School of Medicine.
"Initially, getting stronger glasses may be all it takes to improve vision," says Dr. Cykiert. But having the clouded lens surgically removed is the only way to restore sight once cataracts make life a blur. After its removal, people who do not have other eye disorders or problems during the surgery usually have a clear plastic lens implanted that becomes a permanent part of the eye.
The newest option: multifocal intraocular lenses-sold as ReSTOR, ReZoom and Crystalens-that allow most patients to get rid of their glasses as well as their cataracts. Due to their unique technology, these lenses focus light much like the healthy eye does, so people have good vision at all distances, says Dr. Cykiert, who prefers ReSTOR lenses because they provide better near vision. The standard rigid artificial lens, on the other hand, provides clear vision only at a singular, predetermined distance-near, intermediate or far.
Though opting for multifocal intraocular lenses may allow patients to go from near blind to 20/20 vision in 20 minutes, Medicare patients must pay an extra out-of-pocket charge of about $1,200 to $2,500 per eye (insurance covers only the cost of a standard artificial lens). Regardless of the lens type chosen, cataract surgery is usually an outpatient procedure. In the most common method, the doctor makes a tiny incision in the cornea and inserts a needle-thin ultrasonic probe that dissolves the cloudy lens so it can be suctioned out. If both eyes have cataracts, surgery is performed on one eye at a time, usually eight weeks apart.
Cataract surgery is safe and effective. Studies show that about 90 percent of patients see better after the procedure. If multifocal intraocular lenses are implanted, "only about ten percent of patients still need to wear glasses occasionally," says Dr. Cykiert.
Glaucoma
It is called the "silent thief of sight." More than 2.2 million Americans have the most common form of glaucoma, which is caused by abnormal fluid pressure within the eye. But half don't know it because there are no early symptoms. By the time victims notice that they have lost some peripheral vision, it's too late to restore that missing sight. Fortunately, regular dilated-eye exams can detect glaucoma early and treatment can keep most sufferers seeing well for life.
"Research has shown that lowering eye pressure in people at high risk reduces their chances of getting glaucoma or slows the rate of progressive vision loss if they already have the disease," says Kuldev Singh, MD, a professor of ophthalmology at Stanford University. Although anyone can get glaucoma, those at greatest risk are African-Americans over age 40, everyone over age 60 and people with a family history of the disease.
Most cases of glaucoma occur when fluid constantly produced by the eye doesn't drain properly, increasing pressure within the eye that gradually destroys optic nerve fibers essential for sight. As the disease worsens, the field of vision narrows and blindness results. To lower the pressure, doctors initially prescribe eye drops and/or oral medications that either slow fluid production or speed drainage. For early-stage glaucoma, treatment can be so effective that it may partially reverse nerve damage, according to Research to Prevent Blindness, a charitable organization that funds vision research. In a recent study, 40 percent of patients with little or no vision loss who used pressure-lowering drops showed improved retinal nerve cell function.
But eye drops are only successful if glaucoma sufferers take them as directed-and many don't. One study found that more than half of patients used eye drops incorrectly; another revealed they took, at best, only 76 percent of prescribed drops. Some patients skip or incorrectly time doses; others don't apply the drops properly, so the medication runs out of the eye or gets absorbed into the blood. Failing to follow the treatment regimen can double the rate of vision loss, according to experts at Johns Hopkins University.
To remember doses, the patient can try pairing "eye-drop time" with another daily activity, such as tooth brushing (for a twice-daily dose) or meals (for multiple doses). To be sure enough medication gets into the eye, ask your doctor for instructions on administering the drops. One effective maneuver: Once the drops are in, have the patient close his or her eyes and press a clean finger against the inner corner for two minutes. If you need to apply more than one eye drop, wait five minutes so the second drug won't wash out the first.
If drugs don't lower eye pressure enough or cause intolerable side effects, laser treatment or glaucoma filtration surgery can increase drainage. But surgery should be done only if medication and laser treatment fail, says Dr. Singh. "The new drainage channel that is created may lead to decreased vision, due to cataract formation and other causes."
Age-Related Macular Degeneration
Time takes its toll on the macula, the area of the eye that's responsible for the sharp central vision necessary for reading, watching TV and driving. By age 75, one-third of Americans will suffer some form of age-related macular degeneration (AMD), the leading cause of irreversible blindness. Though genes play a part, AMD has been linked to cell damage caused by poor nutrition, sunlight and/or tobacco smoke (both smoking and daily exposure to secondhand smoke increase risk, suggests a 2005 study).
There are two types of AMD-dry and wet. The 10 percent of AMD sufferers who develop the wet form, first have the dry. It occurs when light-sensing cells and blood vessels break down, causing deposits behind the retina. Dry AMD progresses so slowly that the disease is often moderately severe by the time sufferers experience symptoms, such as a blurred spot in the center of their vision, says Dr. Cykiert.
However, if dry macular degeneration turns into wet, straight lines may suddenly appear wavy. Wet AMD, which rapidly leads to severe vision loss, occurs when abnormal blood vessels grow behind the macula and leak eye-damaging fluid and blood. "When these vessels leak fluid, they create a small bump in the retina that distorts vision, so a normally straight door frame looks curved," explains Dr. Cykiert.
Though there is no cure for wet AMD, destroying abnormal vessels with a laser plus a light-sensitive drug has been shown to stabilize or improve vision in up to 60 percent of patients, according to the American Academy of Ophthalmology. Another treatment, monthly injections of a vessel-inhibiting drug, pegaptanib (Macugen), into the anesthesia-numbed eye, can help prevent further vision loss and even improve vision in some cases.
Currently, the only effective treatment for dry AMD is nutritional therapy. The National Eye Institute's (NEI) Age-Related Eye Disease Study found that high levels of certain nutrients can reduce the risk of vision loss by about 25 percent in patients with early or intermediate AMD in one or both eyes as well as in those with advanced AMD in one eye. The study-proven formula, which can be found in Ocuvite PreserVision as well as generic eye supplements, contains 500 milligrams (mg) of vitamin C, 400 international units of vitamin E, 80 mg of zinc oxide, 15 mg of beta-carotene and 2 mg of copper (as cupric oxide).
A diet chock-full of these same antioxidants may reduce the odds of developing macular degeneration by 35 percent, suggests a new Dutch study. Serving lots of fruits, vegetables, fish, nuts and whole grains should provide enough of these sight-saving vitamins and minerals, especially if the menu regularly includes carrots, citrus fruits and dark leafy greens such as spinach.
"If people start eating these things now, it may prevent problems in ten, fifteen or twenty years," says Dr. Cykiert, who also recommends this diet to patients with AMD.
Encourage loved ones with AMD to eat right, take vision supplements, and, if necessary, lose excess pounds and quit smoking. Current evidence suggests that being overweight and smoking increase the likelihood that early AMD will advance.
Diabetic Retinopathy
Nearly half of people with diabetes will develop some degree of diabetic retinopathy, the leading cause of blindness in Americans under age 65. People with pre-diabetes-higher-than-healthy blood sugar levels-are also at risk, suggests a recent study. Unfortunately, one-third of the 18 million Americans with full-blown diabetes and most of the 41 million with pre-diabetes don't know they have it because they haven't had their blood sugar tested.
High blood sugar damages the blood vessels that nourish the retina. Eventually these weakened vessels may seep fluid, causing part of the retina to swell, which blurs vision. As the disease progresses, fragile new blood vessels can form. These may rupture and bleed into the eye, causing sudden vision loss.
However, "diabetic retinopathy often has no early warning signs," says Monique S. Roy, MD, director of the Medical Retinal Service at the University of Medicine and Dentistry (UMDNJ)-New Jersey Medical School in Newark. "The key to preventing vision loss is for diabetics to have yearly dilated-eye exams and for people newly diagnosed with type 2 diabetes to be screened immediately for retinopathy."
Early diagnosis and treatment of retinopathy can reduce the risk of blindness by 95 percent, according to an NEI-sponsored study. But to stop diabetes from stealing sight, eyes must be treated before there is significant retinal damage. Common procedures include injections to help reduce blood leakage, laser treatment to seal or destroy leaking blood vessels and surgical removal of blood from the eye. "Laser treatment alone will reduce the risk of severe vision loss by more than fifty percent in people with severe retinopathy—either leakage or abnormal vessels," says Dr. Roy.
To save their eyesight, people with diabetes must keep their blood pressure and blood sugar at near-normal levels by following a doctor-prescribed program of diet, exercise and possibly medication.
"Good sugar control may decrease the risk of retinopathy by as much as seventy-five percent," says Dr. Roy. "It can also slow the progression of the disease and prevent future vision loss in people with retinopathy."
Careful control requires regular blood-sugar checks by patients or caregivers and doctors. According to the American Diabetes Association, all who have diabetes should have a lab test that measures hemoglobin A1C, which reflects glucose control over the preceding three months, at least twice a year. The goal range is less than seven percent, but every one-point reduction in A1C cuts the risk of eye damage by 40 percent.
Most eye diseases are treatable, especially if caught early. "Your best defense against diseases that pose the greatest threats to vision is an eye exam," says Dr. Cykiert. So don't delay—make an appointment today!