Windows on the world: Take good care of your eyes

by Kate A. Griffith

Every morning you wake up, open your eyes and take in the world around you. If you wear corrective eyewear, that view may be fuzzy, or downright incomprehensible, until your hand lands on your glasses and your glasses land on your face.

If you’re one of the few with perfect – or acceptable – uncorrected vision …seeing the world clearly as each new day begins is something you probably take for granted.

Whether your vision needs correction or not, you depend on your eyes from the moment you wake up to the moment you go to sleep. That’s a mighty responsibility for one of your body’s most delicate organs.

On a daily basis, your eyes have to battle damaging free radicals and the normal changes that come with aging.

Most of us know that eye health changes are inevitable with aging… or are they?

Our eyes are very complex organs. In order for our eyes to see, there must be light. Light rays reflect off an object and enter the eye through the cornea. At the back of the eye the light is focused by the retina, and then it is converted into electric signals to be sent to the brain.

Once the brain receives the signals, vision occurs. If the eye cannot properly focus an image it is said to have a refractive error. An eye doctor can determine the type of refractive error by a test called refraction. Correcting a refractive error is achieved by glasses, contacts or refractive surgery.

Presbyopia

This common change in vision generally sets in after age 40, and generally sends you to the eye doctor (or the spinner rack at the pharmacy) for a pair of reading glasses. Most people notice a very gradual change that begins with simply holding things a little further away than they used to.

Presbyopia is a condition where the eye exhibits a progressively diminished ability to focus on near objects. It’s most noticeable when you’re trying to read the fine print in newspapers or magazines, and of course, reading labels.

It is not known with certainty what causes presbyopia. Some evidence supports a loss of elasticity of the crystalline structure and changes in the curvature of the lens from continual growth. Loss of power in the muscles that bend and straighten the lens may also cause this common age-related challenge.

Cataracts

According to the National Eye Institute, more than half of all Americans over the age of 65 have cataracts—a clouding of the lens of the eye that can impair vision.

Cataracts are a buildup of protein that clouds the lens. This cloudiness prevents light from passing through a normally clear lens, causing some loss of vision.

There are several types of cataracts. They include:

• Age-related cataracts. The most common type, which develop as a result of aging.
• Congenital cataracts. Babies are sometimes born with cataracts as a result of an infection they had before they were born. These may also develop during childhood.
• Secondary cataracts. Diseases, like diabetes, long-term exposure to toxic substances, certain medications (such as corticosteroids or diuretics), ultraviolet light and radiation may cause the lens of the eye to become cloudy.
• Traumatic cataracts. Injury to the eye may cause cataracts to form.
   

Other factors can increase a person’s risk of developing this condition, including exposure to cigarette smoke and air pollution, or heavy alcohol consumption.

Symptoms

Cataracts often form slowly and cause few symptoms. When symptoms are present, they can include:

• Vision that is cloudy, blurry, foggy or filmy
• Sudden nearsightedness
• Fading or yellowing of colors
• Poor night vision
• Problems with glare and light sensitivity
• Double vision (usually in one eye)
• Sudden temporary improvement in close-up vision
• Prescription changes
• Needing brighter light to read

Macular degeneration

Normal Vision

The same scene as viewed by a person with age-related macular degeneration.

The same scene as viewed by a person with cataracts. Images courtesy of the National Eye Institute, a division of the U.S. National Institutes of Health.

Age-related macular degeneration (AMD) is the result of damage to the nerve cells in a small area at the back of your eye called the macula. AMD causes blurring of your central vision, making it harder to do things that require sharp vision, such as reading, driving and recognizing faces.

There are two types of AMD: wet (exudative) and dry (atrophic). The dry form accounts for about 9 out of 10 cases of AMD. The wet form is much less common, but it happens more quickly and is more severe.

Dry AMD

The dry form of macular degeneration occurs gradually and usually begins with the formation of tiny yellow deposits in the macula called drusen. Drusen usually do not cause serious loss of vision, but can cause distortion of vision. Sometimes drusen will cause the macula to thin and break down, slowly leading to vision loss. Several things are thought to play a part in the development of macular degeneration.

Those who are more likely to have AMD:

• Are older adults—the risk increases as you age, starting around age 50.

• Have a close family member who has macular degeneration.

• Smoke.

• Eat a diet that is low in antioxidants and zinc.

• Are deficient in lutein.

Those with macular degeneration first notice dim or fuzzy central vision. Things may look warped or smaller than they really are, and they may notice a blank or blind spot in the center of their field of vision. As the disease gets worse, those with AMD have trouble with tasks like reading and driving.

If you have the dry form of AMD, your vision will probably become blurry so slowly that you won’t notice it for a long time. You may have AMD for several years before it becomes apparent.

How is AMD diagnosed?

A doctor can usually detect AMD by doing a regular eye exam and asking questions about your past health. You may have some vision tests, including an ophthalmoscopy. This test lets your doctor look at the inside of your eye. If you have macular degeneration, your doctor may see the yellowish drusen deposits.

The doctor may have you look at a chart with lines and a dot at the center called an Amsler grid. It can help detect changes in your central vision.

Numerous studies have shown that the nutrient lutein is deposited in the macula and the lens of the eyes. Researchers believe that supplementing with lutein reduces the risk of AMD.

Wet AMD

Wet macular degeneration occurs in about 10 percent of AMD patients. It happens when abnormal blood vessels grow in the back of the eye. These blood vessels break easily and leak blood and fluid under the macula. This can quickly damage the macula and distort your central vision.

Wet AMD typically causes significant vision problems in the affected eye and can progress very rapidly, causing permanent central vision loss. The wet form of AMD can cause serious vision loss within months or even weeks. People who have the wet form have the dry form first.

What are the symptoms of wet AMD?

Often the first symptom of the wet form of AMD is that straight lines look wavy, curved or broken. Dark spots, lines or shadows begin to appear in the middle of the field of vision. Also, the ability to see fine details when looking at an object—no matter how close or far away it is—begins to decline.

If you think you might have wet macular degeneration, see your doctor immediately. In some cases, quick treatment may help you keep your central vision.

What causes macular degeneration?

The exact cause of AMD is not known. Smoking, exposure to direct sunlight over a period of years, a lack of vitamin A and some medical conditions increase the likelihood of developing the condition. AMD also seems to be inherited. However, none of these things can really be said to cause macular degeneration.

Does AMD always lead to blindness?

Even though vision might be blurry or lost in the middle of the field of view, macular degeneration does not affect vision off to the side. People with macular degeneration have a good chance of keeping useful vision for many years.

Glaucoma

Glaucoma is a condition that is characterized by increased pressure in the eye that results in impaired eyesight, ranging from slight vision loss to total blindness. Glaucoma is not a single disease, but a group of eye diseases that have one feature in common: progressive damage to the optic nerve caused by increased pressure within the eyeball. The pressure comes from a clear fluid called the aqueous humor. This fluid helps to nourish the eye, and flows in and out of the eye through a mesh-like channel. In people with glaucoma, the fluid does not drain properly and pressure builds up in the eye, damaging the nerve that transmits images to the brain. As this deterioration of the optic nerve continues, vision worsens, and eventually, blindness can result.

Symptoms

With the most common form of glaucoma (known as open-angle glaucoma), the only symptom you are likely to notice is vision loss. You may not notice the vision loss until it is severe, because your less affected eye at first makes up for the loss. Side (peripheral) vision is usually lost before central vision. Because the disease can be present long before symptoms arise—annual pressure checks are recommended for anyone over 50. Younger persons with a genetic link to glaucoma should also undergo frequent exams.

Prevalence, Cause and Treatment

Currently, an estimated 2 million Americans are thought to have glaucoma with only 50 percent of those undergoing treatment. Over 100,000 Americans are blind due to glaucoma.

Although the cause is unknown, some interesting research looks at a possible link between the food additive MSG and use of steroid inhalers in some glaucoma sufferers (see "More Evidence Against Processed Foods").

Drops to reduce pressure are the most commonly prescribed treatment for glaucoma. Glaucoma can’t be cured, and damage caused by the disease can’t be reversed. But with treatment, glaucoma can be controlled.