What is a cataract?
A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. Cataracts are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. A cataract can occur in either or both eyes. It cannot spread from one eye to the other.
What is the lens?
The lens is a clear part of the eye that helps to focus light, or an image, on the retina. The retina is the light-sensitive tissue at the back of the eye.
In a normal eye, light passes through the transparent lens to the retina. Once it reaches the retina, light is changed into nerve signals that are sent to the brain. The lens must be clear for the retina to receive a sharp image. If the lens is cloudy from a cataract, the image you see will be blurred.
How do cataracts affect vision?
Age-related cataracts can affect your vision in two ways:
Clumps of protein reduce the sharpness of the image reaching the retina.
The lens consists mostly of water and protein. When the protein clumps up, it clouds the lens and reduces the light that reaches the retina. The clouding may become severe enough to cause blurred vision. Most age-related cataracts develop from protein clumpings.
When a cataract is small, the cloudiness affects only a small part of the lens. You may not notice any changes in your vision. Cataracts tend to “grow” slowly, so vision gets worse gradually. Over time, the cloudy area in the lens may get larger, and the cataract may increase in size. Seeing may become more difficult. Your vision may get duller or blurrier.
The clear lens slowly changes to a yellowish/brownish color, adding a brownish tint to vision.
As the clear lens slowly colors with age, your vision gradually may acquire a brownish shade. At first, the amount of tinting may be small and may not cause a vision problem. Over time, increased tinting may make it more difficult to read and perform other routine activities. This gradual change in the amount of tinting does not affect the sharpness of the image transmitted to the retina.
If you have advanced lens discoloration, you may not be able to identify blues and purples. You may be wearing what you believe to be a pair of black socks, only to find out from friends that you are wearing purple socks.
What are the symptoms of a cataract?
The most common symptoms of a cataract are:
Cloudy or blurry vision.
Colors seem faded.
Glare. Headlights, lamps, or sunlight may appear too bright. A halo may appear around lights.
Poor night vision.
Double vision or multiple images in one eye. (This symptom may clear as the cataract gets larger.)
Frequent prescription changes in your eyeglasses or contact lenses.
How is a cataract detected?
Cataract is detected through a comprehensive eye exam that includes:
Visual acuity test. This eye chart test measures how well you see at various distances.
Dilated eye exam. Drops are placed in your eyes to widen, or dilate, the pupils. Your eye care professional uses a special magnifying lens to examine your retina and optic nerve for signs of damage and other eye problems. After the exam, your close-up vision may remain blurred for several hours.
Tonometry. An instrument measures the pressure inside the eye. Numbing drops may be applied to your eye for this test.
Your eye care professional also may do other tests to learn more about the structure and health of your eye.
Reference: Facts About Cataract (2015, Sept.) Retrieved from https://nei.nih.gov/health/cataract/cataract_facts