The Eyes Have It
If your eyes are functioning well, it’s easy to take good vision for granted. But that would be a mistake. As changes can occur in other systems of the body, so also can eyes sustain injury or develop problems at any point in the lifespan, says Dr. Christopher Chapman, section chief in the Ophthalmology Department at Dartmouth Medical Center.
Even newborn infants can have problems, he says. Premature infants are at risk of retinopathy of prematurity. If not diagnosed and treated promptly, there is a risk for early and rapidly advancing glaucoma and/or blindness. The condition is difficult to identify at the early stage but a new technique for microscopic inspection is “on the horizon.”
Children are especially vulnerable to ocular trauma. Dr. Chapman is emphatic about the need to wear protective eyewear for sports. A blow to the head can lead to bleeding inside the eye and increased risk for eye disease. Prevention and safety education should be included in all sports programs, and Chapman urges parents to raise this issue if it is not being addressed.
New procedures offer new ways to deal with the common vision problems of myopia (nearsightedness) and hyperopia (farsightedness), conditions that result from variations in the shape of the eye, not from a disease process. Many people come to Dartmouth Hitchcock’s Laser Vision Center for Lasik surgery to reduce dependence on corrective lenses. In this procedure a laser beam reshapes the cornea to achieve the refraction needed to correct either near or farsightedness. The change is permanent. But Lasik is not for everyone — people with refractory instability (frequent changes in corrective lenses), are under age 25 or have an eye disease would not be good candidates.
Toric lenses make it possible for people with astigmatism to wear contacts. A toric lens is not a perfect sphere, but rather has a slightly elongated curve on two sides. This allows for the two kinds of correction needed. Lens implants, typically used to replace a lens clouded by cataract, may also be used for refractory correction. “The technology changes so fast,” says Chapman, “that journals are out of date in six months.”
Conditions that develop over time include cataracts, glaucoma and macular degeneration. “Though more common after age 50,” Dr. Chapman says, “they can occur earlier. I recommend eye examinations every two or three years in your 40s.”
A cataract is a lens that has become opaque, or cloudy. This opaque film interferes with vision and can lead to blindness if not treated. Fortunately, says Dr. Chapman, surgery is safe and effective. The lens is surgically removed, using high frequency ultrasound. Operating time is brief and can be performed in an outpatient setting. A high-grade plastic lens is inserted immediately and usually fits in perfectly. Any surgery, however, carries some risk. The risks in cataract surgery include possible swelling in the macula and inflammation. But with new medications and anti-inflammatory drugs, even complications are easier to treat, Dr. Chapman says.
There has been an increase in diagnosis and treatment of cataracts, which is attributed primarily to an aging population and better options for treatment. Causal factors may include excessive exposure to ultraviolet light, a history of smoking, presence of diabetes and genetic predisposition.
Macular degeneration, often called age-related macular degeneration, is much more prevalent among persons age 65 and older. With the more prevalent “dry form,” the center of the inner lining of the eye, the macular area of the retina, thins and atrophies. Gradually, central vision is lost. There is as yet no treatment for cataracts but vitamin therapy with high doses of certain antioxidants seems to slow the progression.
In the vascular or “wet form” of macular degeneration, there is blood and protein leakage below the macula. A rapid loss of vision occurs. Until recently there was no treatment. Now the administration of anti-VEGF agents (Vascula Endothalial Growth Factor) has been shown to achieve regression of abnormal blood vessels and some improvement in vision. The drugs are injected directly into the eye, but Dr. Chapman expects they will be available in drop form within five years.
Glaucoma is actually a cluster of diseases of the optic nerve. Worldwide, glaucoma is the second leading cause of blindness. It is more prevalent in older adults but may begin in early middle age and progress slowly, undetected over many years.
Damage to the optic nerve results in loss of peripheral vision. It is usually the resul
t of inadequate drainage of optic fluid. High optic pressure is a primary risk factor though low pressure does not eliminate the possibility of glaucoma and high pressure does not always indicate its presence.
There is no treatment that restores the damaged optic nerve. There are, however, treatments that can stop or slow the progression of the disease. For many patients, eye drops are effective. Laser treatment to improve drainage of optic fluid is often successful; surgery to increase drainage and lower optic pressure is another option.
Risk factors include age (over 50), family history of glaucoma and presence of diabetes or hypertension. African Americans and Hispanics are especially vulnerable to glaucoma.
Dr. Chapman is optimistic about ongoing research in ophthalmology. He states that in the next 20 years we will have identified the genes that are responsible for genetic eye diseases, such as retinitis pigmentosa, an inherited disease that usually begins in childhood or youth and causes degeneration of the rods and cones of the eye. Gene therapy and sophisticated nanotechnologies will make diagnosis more precise and treatment more effective.
Vision is a precious commodity at every age. What can we do to preserve our vision? Regular eye exams are important. Dr. Chapman suggests that one do an occasional at-home check of each eye separately. Cover first one eye, then the other, to make sure that one hasn’t changed. He says that our eyes work together to compensate for change, so decline in one eye may go unnoticed.
Maintaining good overall health is critical. Don’t smoke. Avoid excessive light exposure — wear good quality sunglasses for outdoor activities. Wear protective lenses for sports and activities such as cutting wood. Control blood pressure and blood sugar. Eat a diet rich in fruits and vegetables, low in saturated fats. A growing body of research indicates a connection between eye health and diet. Didn’t our mothers tell us to eat our carrots and spinach?
“Going into the eye is fascinating,” says Dr. Chapman, as he reflects on the intricate network that he sees in an examination. “The eye is a reflection of what’s going on in the body.” NH