A cataract is a progressive, painless clouding of the natural, internal lens of the eye. Cataracts block light, making it difficult to see clearly. Over an extended period of time, cataracts can cause blindness. They’re often related to growing older, but sometimes they can develop in younger people.
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.
Causes and Risk Factors
What causes cataracts?
The lens lies behind the iris and the pupil. It works much like a camera lens. It focuses light onto the retina at the back of the eye, where an image is recorded. The lens also adjusts the eye’s focus, letting us see things clearly both up close and far away. The lens is made of mostly water and protein. The protein is arranged in a precise way that keeps the lens clear and lets light pass through it.
But as we age, some of the protein may clump together and start to cloud a small area of the lens. This is a cataract. Over time, the cataract may grow larger and cloud more of the lens, making it harder to see.
How can cataracts affect my 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 clumping.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 Cataracts?
Cataracts usually form slowly and cause few symptoms until they noticeably block light. When symptoms are present, they can include:
- Vision that is cloudy, blurry, foggy, or filmy
- Progressive nearsightedness in older people often called “second sight” because although their distance vision is deteriorating, they may no longer need reading glasses.
- Changes in the way you see color because the discolored lens acts as a filter.
- Problems driving at night such as glare from oncoming headlights.
- Problems with glare during the day.
- Double vision while looking through the eye with a cataract (like a superimposed image).
- Sudden changes in glasses prescription.
When are you most likely to have a cataract?
The term “age-related” is a little misleading. You don’t have to be a senior citizen to get this type of cataract. In fact, people can have an age-related cataract in their 40s and 50s. But during middle age, most cataracts are small and do not affect vision. It is after age 60 that most cataracts steal vision.
Who is at risk for cataract?
The risk of cataract increases as you get older. Other risk factors for cataract include:
- Certain diseases such as diabetes.
- Personal behavior such as smoking and alcohol use.
- The environment such as prolonged exposure to sunlight.
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.
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