Many people develop cortical cataracts with age. These cataracts begin as whitish, wedge-shaped opaque areas on the outer edge of the lens cortex, near the capsule. Slowly, these opacities become streaks reaching inward to the center of the lens, like spokes on a wheel. When they reach the center, they block part of the light passing through the nucleus of the lens, and you will begin to have problems with focusing, distortion, and glare.
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Because both distance and near vision are impaired, you may require surgery at a comparatively early stage. If you have diabetes, you may be particularly susceptible to cortical cataracts.
Subcapsular Cataracts
When a subcapsular cataract begins at the back of the lens, which is most often the case, it's called a posterior subcapsular cataract. It starts out as a grainlike opaque area under the lens capsule. Because posterior subcapsular cataracts are usually directly in the path of light on its way to the retina, you might have vision problems early on, particularly with glare and halos.
Anyone can have subcapsular cataracts in one or both eyes. People who are extremely nearsighted, who have diabetes, or who are taking high doses of steroids are particularly at risk.
How Common Are Cataracts?
Nearly everyone will eventually have cataracts. Estimates differ because not all who are affected seek treatment, but current research indicates that by age seventy-five at least 70 percent of Americans either have had cataract surgery or cannot see well because of cataracts. You'll likely begin to notice cataract-related vision problems in your early to mid-sixties.
Cataract surgery is the most common surgical procedure in the United States. Some 3 million Americans have cataract surgery every year, often in an outpatient procedure that takes less than ten to fifteen minutes. The surgeon replaces the clouded natural lens with a clear synthetic lens through a tiny incision. These procedures nearly always succeed in greatly improving the patient's vision, with almost no interruption in daily activities.
How Do Cataracts Affect the Eyes?
As explained earlier, all light entering the eye passes through the lens. Your lens must be clear for light to focus properly on the retina. Therefore, any clouding of the lens will affect your vision to some extent.
In most people, cataracts develop gradually and their eyesight may be adequate for several years before surgery is necessary. Other people experience more-rapid progression of cataracts, especially if several areas of the lens are affected. Cataracts that form directly behind the pupil are likely to cause problems sooner than cataracts closer to the edges of the lens.
As more and more of the lens becomes opaque, the clouded areas scatter the light that enters and prevent it from focusing properly on the retina. If you have cataracts, sensitivity to glare might make it hard to drive at night. You might see halos around lights. Your vision might be blurred or hazy - like trying to see through a waterfall. (In fact, it might be that sensation that gave cataracts their name: The Latin term for "waterfall" is cataracta. Another theory is that the whitish color of an eye cataract is similar to the color of turbulent water, as in a waterfall.)
Eventually, the lens takes on a yellow or brown tinge, which affects your ability to distinguish colors, particularly shades of purple and blue. Again, these changes might occur so slowly that you don't notice them until someone points out that your socks don't match!
Age-related cataracts don't spread from one eye to the other, though they typically develop at about the same rate in both eyes. Cataracts, if neglected, can advance to the point where the pupils appear milky. These cataracts are referred to as ripe or mature. (At one time, patients were advised to wait until their cataracts were ripe before having surgery. This approach was abandoned long ago.)
Immature cataracts, in which there are still clear areas of the lens, are generally not visible except to the doctor who is examining your eyes. You would almost surely notice significant vision changes and seek treatment long before your cataracts were ripe and visible to the naked eye.
Unless they are persistently ignored and become overripe, cataracts do not cause discomfort - itching, burning, or aching - or a discharge from your eye, nor do they create redness, swelling, or inflammation. If you have symptoms such as these, see your eye doctor to find out what is causing them. To find out more, you can check out Does Cataract Surgery Correct Vision.