Without a doubt, vision is the function we use most in relating to our environment. Of the many nerve fibers transmitting information to the brain, nearly 40% are inside the two optic nerves which connect the eyes to the brain.
In addition, almost all higher cerebral functions connect with the part of the brain that serves vision. If you hear a sound, you turn to look for its source. If you notice a fragrance, you look for its origin. If someone touches you on the shoulder, you look at the person, and of course, if you note an object in your peripheral field, you move your eyes to look directly at the object.
So the changes in the eye caused by aging are especially important. The chart on pages 4-5 will help you review the physical details. Here are common problems, and how to tell the expected signs of aging from the serious symptoms of a medical problem.
Some of the most common problems we see which are related to eye discomfort include eyelid spasm, a dry eye condition and too many tears.
For little-understood reasons, some people suffer severe spasms, lasting from seconds to minutes, of the lid muscles on one or both eyes. Called blepharospasm, it can interfere with daily functioning if this is severe enough, and treatment is recommended.
Another kind of muscle spasm can cause the edge of the lower eyelid to turn in. With each blink, the eyelashes rub against the cornea. If not corrected with surgery, this leads to chronic irritation of the cornea.
The opposite problem failing muscle tone can weaken the muscle which normally holds the upper lid open. If severe, the upper lids may droop nearly closed, impairing vision. Surgery can correct this problem.
The upper and lower lids normally hug the globe of the eye but with age, the eyelid-closing muscles lose their tone and begin to sag. When the lower eyelid sags, tears do not drain properly.
A variety of growths can also appear on the lids. If this is the case, you should see your doctor.
A dry eye feels gritty, as though scraped by a foreign body. Weakened lid muscles that do not close completely during sleep can make this worse by allowing the cornea to become dry and scratchy-feeling.
A lack of mucous cells in the conjunctiva can also lead to dry eyes with symptoms of a gritty feeling in the eyes, chronic irritation and redness.
Other causes include chronic fatigue of the eye muscles due to lack of sleep, poor health, a latent eye muscle imbalance, or reading when you’re very tired.
Your doctor may suggest using artificial tears to relieve these symptoms which usually are not serious.
Too Many Tears
Severe tearing, as tears run down the cheeks, is another complaint. This usually results from the lower lid drooping away from the eyeball so tears do not drain to the nose. It is worse in cold weather when tear production usually increases. Too much tearing is not serious and is vastly preferable to dry eyes, so use your handkerchief.
Headaches are closely related to the use of the eyes. Two general types are often seen in the elderly patient.
A tension headache comes from increased muscle tone, whether from stress, pain from arthritis, fatigue, or anxiety. Over time, any of these can lead to painful chronic spasm in the muscles of the scalp, the face, or the six muscles that control eye movements. Such tension headaches, usually described as a tight band or pressure about the head, are usually triggered by a specific activity and are made worse by continuing the activity. The truly debilitating pain of tension headaches can often be relieved by muscle relaxants or aspirin.
Pain in the muscles which control eye movement often causes a brow ache. It first appears when you wake up in the morning, especially after a late night of reading or television watching. The pain can take the form of a throbbing dull ache behind one or both eyes, or spread across the brow or even the entire forehead. It can involve either side of the head.
This type of headache results from an aging-related tendency of the eyes to drift outward, or to diverge. This is due to loss of tone in the muscles which turn the eyes inwards during reading and close-up work. As the eyes drift outward, the eye’s inward-turning muscles try to counteract. All this constant effort leads to fatigue that is similar to strained arm or leg muscles. Avoid this kind of headache by getting more rest, or doing your work early in the day when you are fresh.
Problems With Vision
Opacities in the vitreous are opaque spots or bits that have broken from attachment to the periphery of the retina and now float freely. People notice these as lightning flashes in the peripheral vision. Near-sighted people and those age 55-65 may see lines, spots, webs and clusters of dots moving slowly across the field of vision. Usually they move faster with eye movements and may become stationary when the eye is not moving. While annoying, these are not cause for alarm. As you learn to ignore them, they become less noticeable.
Another age-related change in the vitreous can be a general haziness. While this also is usually not serious, it is wise to check with your doctor.
Decreased vision related to glare is a frequently heard complaint. As the eye ages, there are changes in both the lens and vitreous humor that result in increased light scattering.
Opacities in the periphery, or outer edges, of the lens, do not directly interfer with vision. But they can increase scattering of light as it passes through the lens. At night when the pupil is slightly dilated this is especially noticeable. Further contributing to this light scatter are strands and opacities of various shapes within the vitreous humor. So it is no wonder that the elderly complain of the glare from oncoming headlights while driving at night. As long as vision remains sharp, we suggest either not driving at night or not looking directly at headlights.
Daytime glare can also be a problem. With age, opacities may develop in the central cortex just beneath the back of the lens. These opacities tend to scatter light even more than opacities elsewhere in the lens. The early sign of their existance may be increased glare, especially in bright light. Mild dilation of the pupil and wearing of sunglasses may give temporary relief. However, you should consult an ophthalmologist about these and other strategies.
Adjusting To Light Changes
As age reduces pupil size so less light enters the eye, the elderly often complain that objects are no longer as bright. The aging pupil closes slowly so going outdoors may be dazzling. It is especially hard to see when going from daylight into a darkened theater because aging pupils widen more slowly. However, if your vision otherwise is shapr and clear, there is usually no cause to be concerned.
Tissue from the conjunctiva may accumulate at the corner where the white, or sclera, meets the clear cornea. This growth is called a pterygium. If the pterygium continues to grow and reaches the center of the cornea, it can interfere with vision. Pterygia are usually seen in elderly individuals who are outdoors a lot, especially in dust and wind. Pterygia should be watched, and if the cornea is at risk, surgical removal is recommended.
In the cornea, age-related degeneration of the inner surface can cause fluid to accumulate, swelling the cornea and causing edema. Vision through this corneal edema is hazy. A corneal transplant is often recommended.
With age the vitreous changes, going from being gelatin-like to becoming liquid. As the eye moves, the remaining gelatin-like vitreoustugs on the retina, stimulating it so that a vertical flashing light seems to appear, almost always in the far temporal visual field and in only one eye at a time. If these flashing lights are not accompanied by decreased or other changes in vision, they can be disregarded. However, if they persist and there is the feeling of a veil over the eye or loss of visual field, then schedule an eye exam.
Changes In The Lens
Beginning at about age 45 and progressing through age 65, the lens loses its ability to increase its thickness which is necessary for reading and close work.
Normally, when you look at an object closer than 24 inches, the lens changes shape, thickening to increase its refractive power in order to focus the light from the object onto your retina. Around age 20, the lens begins losing its ability to thicken. This does not begin to interfere with close-up work until about the early 40’s and finally stabilizes by the early 60’s. Called presbyopia, this condition occurs earlier in far-sighted (or hyperopic) people. Presbyopia, which is universal and has no alarming implications, can be corrected by using reading glasses. As near-sighted (ormyopic) people age, they often have an easier time, just taking off their glasses to read small print.
Age-Related Eye Diseases
A cataract is an opacity of the lens which reduces the vision to 2030 or less. The reduction in vision is painless but progressive. People in their 70’s and 80’s are most likely to develop cataracts, because age is the major determining factor. Researchers are still trying to determine the cause of age-related cataracts and the only treatment is cataract surgery. (See Executive Health Report, Vol. 22, No. 10, for a full discussion of cataracts.)
Glaucoma is caused by increased intraocular pressure which impairs the normal function of the optic nerve. In early stages, this disease is symptomless but a simple test from your eye care professional can detect it. Glaucoma damage is irreversible so ask your doctor for the test. Glaucoma accounts for about 10% of all blindness in the United States. (See Executive Health Report, Vol. 25, No. 4, for an in-depth discussion of glaucoma.)
Diabetic Retinopathy (DR)
Diabetic retinopathy (DR) is the third leading cause of adult blindness and accounts for almost 7% of the blindness in the United States. It is associated with long-term diabetes, and therefore, it is sure to become more prevalent as our population continues to age and diabetic patients live longer.
Diabetic patients usually have little or no evidence of DR until they have had diabetes for about 3-5 years. The first serious sign is edema, the collection of fluid in the retina (the seeing part of the eye), at a location that is involved in the best vision–the macula. This macular edema can impair vision. The second serious sign occurs when new blood vessels begin to grow from the retina into the vitreous humor. These new blood vessels bleed easily, hemorrhaging into the vitreous which impairs vision. With recurrent hemorrhages, vision eventually is totally lost.
All diabetic patients should have a comprehensive examination that includes a careful eye examination with pupillary dilation at least once a year to detect any sign of impending vision loss. Since laser treatment can prevent or slow down visual loss at the early stages of macular edema and new blood vessel growth, early diagnosis is vital. Laser treatment has reduced loss of vision by 50% in both conditions.
Age-Related Maculopathy (ARM) has two major causes. A cluster of new blood vessels can grow beneath the retina at the site of the macula. These blood vessels can bleed, damaging the macula. Laser treatment is successful about half the time in stopping the progress of wet ARM.
A second dry type of RAM involves disintegration of the cells which nourish the macula. This eventually kills the macula’s retinal cells, and decreased vision results. At present, we have no treatment for this type of ARM.
Distorted central vision is an early symptom. Objects may appear larger or smaller or straight lines may be distorted, bent or missing a central segment. If this distortion is in one eye alone, you may not notice a change in vision because the unaffected eye will continue to function normally. However, you can compare vision by alternately closing each eye to view an object in order to see any distortion.