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The Aging Eye
Normal Changes in the Aging Eye
Losing Focus
The most common age-related vision change -- presbyopia -- happens to almost everyone beginning between the ages of 40 and 50. A natural result of aging, the lens begins to lose elasticity, making it harder to focus vision up close for such activities as reading. But presbyopia can be corrected easily with reading glasses or glasses with bifocal, trifocal or progressive ("no-line") lenses.
Declining Sensitivity
The lens of the eye also becomes increasingly dense and more yellow with age. These changes may affect color perception and contrast sensitivity. For instance, the color blue may appear darker and harder to distinguish from black. And it may become difficult to tell where an object ends and its background begins, making it difficult to see curbs or steps, for example.
Needing More Light
As the eye ages, the pupil gets smaller, resulting in the
need for more light to see well, along with more time to adjust to
changing levels of illumination (going from daylight into a dark
theater or dimly lit restaurant, for example).
The Four Most Common Causes of Age-Related Vision Loss
In addition to normal changes in vision, older adults may experience eye disorders, health problems or injuries that can permanently affect eyesight -- resulting in blurred or distorted images, or the loss of central or side vision. A number of conditions can potentially impair vision; the most common among them are macular degeneration, glaucoma, cataracts and diabetic retinopathy.
Impaired vision ranges from partial sight (also known as "low vision") to blindness. Low vision cannot be corrected fully to the normal range by ordinary glasses, contact lenses, medication or surgery.
Low vision, however, does not mean "no" vision. And although vision loss may be permanent, much can be done to maximize remaining -- usable -- vision and improve quality of life through vision rehabilitation.
But first and foremost, everyone -- and most especially, older adults -- should have regular eye exams by an ophthalmologist or optometrist to maintain eye health and for early detection of conditions that cause low vision.
Macular Degeneration
What it causes: central vision loss
Warning signs may include:
- gradual, spotty loss of detail vision (dry macular degeneration);
- sudden and severe loss of central vision (wet macular degeneration);
- a need for more light.
Macular degeneration occurs when the macula -- the central part of the retina, which is responsible for detail, color and daylight vision -- is damaged.
When central vision becomes blurred and distorted, reading becomes difficult, color vision is reduced and there is an increased need for light.
There are two types of macular degeneration: dry and wet. The dry variety, which is most common (affecting 90 percent of those with macular degeneration) progresses slowly. And vision changes are much more subtle. When reading, for example, parts of letters may appear to be missing. Straight lines also may appear crooked or wavy (when looking at Venetian blinds, for example).
About 10 percent of people with age-related macular degeneration develop the wet variety, which can come on very suddenly due to leaking blood vessels that have grown in, or under, the retina. The wet type causes severe vision loss and progresses more rapidly than the dry form. A large, dark spot appearing in the center of vision (doctors call this dark area a "scotoma") is typical. If you have a sudden loss of central vision, go to your eye doctor right away.
Risk factors for developing macular degeneration may include high cholesterol, untreated high blood pressure, diabetes and smoking, all of which result in poor circulation to the retina; a lack of certain nutrients needed by the retina; excessive exposure to harmful UV light; and a tendency within families.
Treatment Options
Although there is no cure for macular degeneration, an evolving treatment -- photodynamic therapy -- may slow the progression of wet macular degeneration.
Photodynamic therapy uses a special intravenous dye with a laser to seal leaking blood vessels, and several treatments per year may be necessary.
The National Eye Institute's recent Age-Related Eye Disease Study also showed promising results for patients in the intermediate stage of macular degeneration who took specified doses of antioxidant vitamins and zinc: they lowered the risk of developing more advanced stages of the disease by approximately 25 percent. This formula is now on the market, but be sure to check with your doctor to see if it's recommended for you.
Glaucoma
What it causes: damage to the optic nerve from abnormally high eye pressure or poor circulation.
Warning signs may include:
- subtle loss of contrast;
- difficulty driving at night;
- loss of peripheral vision (late-stage glaucoma).
Glaucoma is caused by progressive damage to the optic nerve, usually resulting from a buildup of fluid pressure inside the eye.
Because there are no obvious early symptoms of glaucoma and it progresses slowly, you may not realize that your field of vision is decreasing. Routine eye examinations and special tests of the visual field are key to detecting glaucoma at an early stage.
Early on, glaucoma causes a subtle loss of contrast between objects and their backgrounds -- for example, not being able to distinguish the curb from the sidewalk or missing a step in a staircase. Many people are uncomfortable or afraid to drive at night because of contrast loss, too.
When glaucoma progresses, the optic nerve damage causes an irreversible loss of peripheral vision. As the condition can be hereditary, people with a family history are at a higher risk, as are all older adults, African-Americans and Hispanic-Americans. Early detection is critical.
Treatment Options
Treatment options for glaucoma are always evolving -- another reason to visit your eye doctor regularly to screen for the condition. And be sure to ask for a contrast test, which can help identify subtle changes in contrast sensitivity due to the loss of retinal cells.
As a rule, elevated eye pressure can be managed with eye drops, medication, laser treatment or surgery. If detected early, eye drops most likely will be prescribed to control the pressure and prevent peripheral vision loss from advancing glaucoma.
Cataracts
What it causes: cloudy vision
Warning signs may include:
- hazy vision;
- trouble distinguishing colors;
- increased sensitivity to glare; light scatters and appears like a "halo."
A cataract is a clouding of the lens that reduces visual acuity, producing an overall haze, loss of contrast and increased sensitivity to glare.
Cataracts diminish the sharpness of detail, resulting in hazy vision, particularly in glaring light. And as the lens becomes more yellow with age, colors may not appear true; it may be difficult to distinguish between navy blue and black, for example. In the advanced stage of cataracts, print appears faded and words become harder to read.
Although the cause of cataracts is unknown, some factors may increase your risk, including: aging, long-term exposure to sunlight, smoking, high cholesterol, diabetes and eye injury.
Treatment Options
A cataract can be removed in a short surgical procedure to replace the affected lens with a plastic one. The most appropriate time for cataract surgery depends partly on its impact on daily activities, bothersome symptoms and maturity of the lens. Although some people have no symptoms, they should have surgery if the lens is hardening and becoming more difficult to remove. There is good news: Cataract surgery has a high success rate in normal eyes. After surgery, patients may need to change their eyeglass prescriptions.
Diabetic Retinopathy
What it causes: hemorrhages in the retina, including the macula
Warning signs may include:
- blurred vision;
- near vision distortion (difficulty reading).
Diabetic retinopathy is one of the complications of advanced or long-term diabetes. It is caused by leaking blood vessels that damage the entire retina, including the macula.
While the effects of diabetic retinopathy vary, near vision can be distorted, and parts of the visual field may be blurred or obstructed.
The most important way that people with diabetes can protect their vision is by monitoring blood glucose levels strictly and visiting an eye doctor who specializes in the treatment of diabetic retinopathy regularly (in addition to being followed medically by a diabetes specialist and a dietitian).
Not everyone with diabetes develops retinopathy, which is why dietary control (low blood glucose) and exercise are so important.
Treatment Options
In the early stages of retinal bleeding, laser treatment of localized areas of leakage can sustain vision levels. And early treatment may prevent the more severe complications of late-stage retinopathy, such as hemorrhage and scar formation, resulting in a detached retina.
Excerpted from the booklet Vision Loss Is Not a Normal Part of Aging (2002) by Eleanor E. Faye, MD, FACS, and Carol J. Sussman-Skalka, CSW, MBA
The material in Vision Loss Is Not a Normal Part of Aging was drawn in part from research funded by the AARP Andrus Foundation, and conducted by the Arlene R. Gordon Research Institute at Lighthouse International. Special thanks to Joann P. Reinhardt, PhD, for summarizing the research findings.
The publication of Vision Loss Is Not a Normal Part of Aging was made possible by a grant from the AARP Andrus Foundation. We also would like to thank the National Eye Institute for supplemental funding.