A cataract is a cloudy or opaque (a nontransparent) area in the lens of the eye.
What is a cataract?
The eyes natural lens is a small oval like structure consisting of a thin capsule enveloping a bag of protein. The protein is crystal clear and colorless. This lens helps to focus light on the retina. The retina is the light-sensitive tissue in the rear of the eye.
In a normal eye, light passes through the transparent natural lens to the retina. Once it reaches the retina, light is changed into nerve impulses that are sent to the brain.
While the lens is clear the retina receives a sharp image. But over the years the lens discolors and becomes opaque. When it becomes so cloudy that it interferes with vision, it is referred to as a cataract. A cataract is a gradual clouding of the human lens inside the eye.
If the lens is cloudy from a cataract, the image you see will be blurred.
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| Normal vision | Blurred vision because of cataract |
Causes
Cataracts can occur at any age but the most common type of cataract is related to aging of the eye. Usually it is first noticed around the age of 50-60. The reason why is not yet known.
For younger people there are factors that can increase the risk of getting cataracts. These include:
- diabetes;
- an injury to the eye;
- exposure to ultraviolet light from sunlight;
- medication use such as long-term use of steroid tablets;
- smoking;
- heavy drinking;
- radiation;
- a family history of cataracts;
- previous eye surgery;
- unknown factors.
Types of cataract
There are mainly three types of cataract:
- Nuclear cataract
- Cortical cataract
- Subcapsular cataract
Nuclear cataracts affect the center of the lens. This type is the most common form of cataract and is associated with the natural aging process. It interferes with the ability to see objects in the distance.
The cortical cataract begins with spoke-like formation extending from the outside of the lens into the center. When the spokes reach the center, blurring and glare result in loss of vision. This type is most commonly seen in patients who have diabetes.
Subcapsular cataracts affect the rear side of the lens, causing glare and blurriness. This type of cataract is usually seen in patients who use steroids, or who suffer from diabetes or extreme nearsightedness.
