Common Causes of Blindness

The National Federation of the Blind reports that 50,000 Americans become blind each year, about one-half of whom are over 65 years of age. Causes of blindness run from long-term illness to eye-damaging accidents. While blindness may be caused by a wide variety of issues, these are some of the most common causes of blindness and the demographics they tend to affect.

Cataracts

• The leading cause of blindness worldwide, a cataract occurs when proteins in the lens of your eye coagulate and form an opaque layer, causing the normally clear lens to become clouded. The exact cause is unknown, but cataracts tend to affect elderly people, implying that they are related to aging. Diabetes and exposure to ultraviolet radiation are both suspected to increase a person's chances of developing cataracts.
  Most cataracts develop quite slowly and cause no pain. At first, eyesight is barely affected at all. If it is, bright lights or strong glasses may be enough to counteract these initial effects. As a cataract continues to develop, however, its interference becomes impossible to ignore. First, it may become difficult to read, see at night or drive a car. Problems seeing things from a distance or dealing with glare soon crop up. Eventually, untreated cataracts cause blindness.
  The only prevention is to remove the cataract, which is an effective and fairly safe surgical procedure, although your doctor may not recommend this immediately. To catch cataracts before serious symptoms set in and maximize your chances of successful treatment, regular eye examinations are imperative.

Glaucoma

• Glaucoma, another extremely common cause of blindness, occurs when the transparent fluid that circulates in the eye fails to drain properly due to blockage, resulting in the build-up of pressure. If not dealt with, this pressure damages the fragile structures in the eye. This build-up is usually slow, producing "chronic glaucoma," but can also happen suddenly, producing "acute glaucoma."
  Chronic glaucoma causes no pain; vision first becomes blurred and then, as pressure increases, peripheral vision is lost and, eventually, chronic glaucoma leads to complete blindness. This condition may be successfully managed with medication, particularly if detected early, but surgery may become necessary.
  Conversely, acute glaucoma is accompanied by severe pain from the fast rise in pressure and requires immediate care. The Hispanic and black population is more likely to suffer from glaucoma, although the precise reason for this is unknown. This condition usually affects people who are older than 40, although it has been seen in children.

Diabetic Retinopathy

• As the name suggests, diabetic retinopathy is caused by diabetes, a disease that affects people of all ages. Diabetic retinopathy is the leading cause of blindness in U.S. adults, affecting the vision of more than 50 percent of the 18 million adults diagnosed with diabetes. Diabetes causes the tiny blood vessels in the retina to form abnormally. If they break, blood is allowed to flow into other parts of the eye, damaging delicate structures along the way. Sometimes, the retina even breaks off from the back of the eye. If detected early, diabetic retinopathy can often be treated with laser surgery to close off affected blood vessels or reattach the retina. Because early detection and careful monitoring of diabetes' effects can make a significant difference in preventing blindness, diabetics should have complete yearly eye exams.

Macular Degeneration

• Macular degeneration causes cells in the macula--the part of the retina that allows you to see fine detail--to die. The disease is a leading cause of blindness among people in the United States who are at least 60 years old and, for this reason, is often called "age-related macular degeneration" (AMD). There is no pain associated with this disease, but it destroys a person's sharp central vision, leaving peripheral vision largely unaffected. AMD can be divided into two types: wet and dry. Wet AMD is the consequence of abnormal blood vessels growing under the macula. Dry AMD results when the light-sensitive macular cells gradually break down. Macular degeneration may advance quite slowly and other times progress rapidly. There is no cure for AMD, but early detection offers the best odds for effective treatment, which may include laser surgery and drugs injected into the eye.

Retinitis Pigmentosa

• How or why retinitis pigmentosa forms remains unknown. What is known is that the condition is hereditary and causes the retina and related vascular area called the choroid to degenerate. Usually excess pigment also develops in the eye. Retinitis pigmentosa usually begins when a person is about 12 years old as night blindness. As it develops, the field of vision narrows. Initially, this narrowing may not be noticeable but, as it progresses, it becomes impossible to ignore. Within a few years, the condition causes "legal blindness." By the time the person reaches adulthood, the field of vision is tiny, and even a small area of vision in the center of the field requires excellent lighting. Most people with retinitis pigmentosa go completely blind as adults. There is no known cure or treatment.

Accidents

• One of the causes of blindness affecting people of all ages is accidental damage to the eye. Injuries to the eyes can occur in a wide variety of ways. Accident-related blindness can be caused by objects that strike the eyes, such as flying debris from a lawn mower, or blunt trauma to the face that injures the optic nerves, such as in an auto accident. Severe burns can cause blindness--either from fire or from exposure to chemicals. In addition, certain professions are at higher risk for eye-related injuries, such as welders who risk blindness if exposed to radiant energy from welding operations or lasers.