What's the problem with cataracts?

"What are cataracts?” and "Do I have cataracts?” are two of the most common questions asked during an eye examination.

What are cataracts? A cataract is formed when the lens of the eye becomes cloudy. The lens is the part of the eye that helps focus light or an image on the retina, the light sensitive tissue at the back of the eye, similar to film in cameras.

When the lens is cloudy, it will interfere with the light entering the eye and imaging on the retina. Hence, vision will be blurred or hazy. Colors will be less vivid or intense and more difficult to distinguish. There may be increased sensitivity to glare from lights, especially when driving at night and difficulty seeing at night. Reading and other routine activities become more difficult to perform.


The two pictures below illustrate the difference in vision between an eye with a normal lens (left) and an eye with a cataract (right).

 Normal VisionVision with Cataract

According to Prevent Blindness America and National Eye Institute, more than 24.4 million Americans in 2012 have cataracts and more than half of all Americans have cataracts or have had cataract surgery by age 80. The World Health Organization has estimated that cataracts are the cause of approximately 51% of all blindness or about 20 million people worldwide in 20101. Most of the blindness from cataracts is seen in underdeveloped nations around the world where access to health care may be extremely limited.  

Most cataracts, approximately 95%2, are age-related, in adults over age 40. Congenital cataracts are seen in babies at birth; these are typically caused by infection, such as rubella or German measles, during pregnancy or possibly inherited. Cataracts can be caused by trauma or damage to the lens, such as a hard blow, cut, puncture, intense heat or chemical burn. Other risks for developing cataracts are diabetes mellitus, certain medication, ultraviolet radiation, smoking, alcohol, and nutritional deficiency. "While there are no clinically proven approaches to preventing cataracts, simple preventive strategies include reducing exposure to sunlight through UV blocking lenses, decreasing or discontinuing smoking and increasing antioxidant vitamin intake through consumption of leafy green vegetables and nutritional supplements."3

A cataract can develop in one or both eyes. It is not contagious and cannot be spread from eye to eye. Cataracts typically develop slowly and can have a range of vision effects from minimal to blindness.

An advanced "Mature" cataract

When there is minimal vision effect, treatment is not needed. Regular eye examinations and self-monitoring of visual changes will be recommended.  When cataracts start to interfere with a person’s daily activities, then surgical intervention may be warranted.  Blindness can occur when cataracts are left untreated and cause significant blockage of light from entering the eye.

In most developing and developed nations, cataract surgery involves removing the lens of the eye and replacing the lens with an artificial lens to restore vision. The artificial lens can greatly improve vision and possibly eliminate the need for eyeglasses.  Cataract surgery is one of the most common procedures performed in the United States with more than two million performed annually.4

1. World Health Organization, 2015
2. Prevent Blindness America, 2012
3. American Optometric Association, 2015
4. Prevent Blindness America, 2013