Cataract is a clouding of the eye's natural lens, which lies behind the iris and the pupil. Cataracts are the most common cause of vision loss in people over age 40 and is the principal cause of blindness in the world.
What Causes Cataracts?
The eye functions much like a camera. Light rays enter the eye, passing through the cornea, the aqueous humor -- transparent fluid in the front of the eye -- and then the pupil and into the lens. The lens bends the light rays to focus objects onto the retina lining the back of the eye. From there, the image passes through the retinal cells, into the optic nerve, and finally to the back of the brain which process the images.
Cataracts occur when there is a buildup of protein in the lens that makes it cloudy. This prevents light from passing clearly through the lens, causing some loss of vision. Since new lens cells form on the outside of the lens, all the older cells are compacted into the center of the lens resulting in the cataract.
Types of cataracts include:
What Are the Symptoms of Cataracts?
Cataracts usually form slowly and cause few symptoms until they noticeably block light. When symptoms are present, they can include:
How Are Cataracts Diagnosed?
An eye exam will be given to test how well you can see (remember to bring your glasses or wear your contacts to the appointment). Your doctor will also dilate your pupil in order to examine the condition of the lens and other parts of the eye.
How Are Cataracts Treated?
If your vision can be corrected to an acceptable level with a change in prescription, eyeglasses, including bifocals or contacts, may be prescribed, eliminating the need for surgery at that time.
If your vision loss cannot be corrected with new glasses and cataracts interfere with your daily life, you may be a candidate for cataract surgery, which involves removing the clouded lens and replacing it with a clear, artificial one.
Talk to your doctor to see which treatment is right for you.
Can Cataracts Be Prevented?
Because the exact cause of cataracts is uncertain, there is no proven method of preventing them. Because cataracts and other conditions such as glaucoma are common in older adults, it's important to have your eyes examined on a regular basis.
This is particularly important if you have risk factors or a family history of eye problems. Adults should see an eye doctor at least every two years and annually after age 50.
People with a history of eye problems or other medical conditions that increase the risk of eye disease -- such as diabetes -- may need eye exams more frequently.
Be sure to ask your doctor if you have any risk factors or indications that cataracts or other conditions may affect your vision.