Accidents are a major cause of blindness. The eye is an extremely delicate organ that you can damage easily. Knives, scissors, pencils and other sharp objects; fireworks and other projectiles; and many different chemicals can partially or completely blind an individual through direct damage.
The lens of your eye focuses light onto the back of your eye. As people get older, the lens can become clouded. This can make your vision dim or blurry, or can even cause double vision. Severe cataracts can cause complete blindness. Fortunately, in many cases, a physician can surgically remove the lens and replace it with an artificial lens, curing the cataract.
Diabetic retinopathy is a disease of the eye that affects people who suffer from diabetes. The disease can damage blood vessels in your retina--the tissue at the back of your eye which senses images. This damage can cause your blood vessels to burst, clouding the retina and damaging or destroying your vision. Sometimes, it even can cause your retina to peel off the tissues that hold it, a condition called retinal detachment.
Glaucoma is a common eye condition among older people. Your eyes are filled with fluid, which has to stay at a certain pressure. Normally, the fluid drains out to keep the pressure at a constant level. As people get older, however, the ducts that allows fluid out of the eye can become blocked, raising the pressure inside the eyeball. This will cause blurred vision at first, but eventually can lead to blindness by damaging the nerves inside the eye. Fortunately, your doctor can prescribe medication to treat glaucoma; in some cases, you may need surgery as well.
The macula is the central portion of the retina. It is responsible for the detailed vision at the center of your eyes. As people age, the macula can start to decline. According to St. Luke's Cataract and Laser Institute in Florida, in about 90 percent of cases of macular degeneration, the retina starts to lose pigment and accumulates yellow deposits known as drusen. This is called dry macular degeneration. In wet macular degeneration (the other 10 percent of cases), abnormal new blood vessels begin to grow into the macula. These blood vessels can hemorrhage, cause scars and induce swelling on the delicate surface of the macula. Both types of macular degeneration cause people to lose central vision as the condition progresses. They can still see movement and shapes out of the corners of their eyes, but can't see shapes or details in front of them.
Retinitis pigmentosa is a progressive degeneration of the rods and cones, the special cells in the back of your eye that detect light. It starts off with poor night vision, but often can progress to total blindness. As the person gets older, he starts to lose peripheral vision and gradually has a narrower and narrower field of vision. He eventually may become totally blind, or may just end up with tunnel vision so narrow that it isn't really useful for anything.