April 24, 2014
   
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Cataracts: Causes, Prevention, Treatment
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Cataracts: Causes, Prevention, Treatment

 
Dr. Shestopalov is Assistant Professor, Bascom Palmer Eye Institute, Department of Ophthalmology, Department of Cell Biology and Anatomy University of Miami Miller School of Medicine, Miami, Florida.


The lens in your eye is normally clear and enables you to see clearly. When the lens becomes clouded with a cataract the world is like a photo you didn't focus properly — everything is fuzzy and indistinct.

Fuzzy vision
Courtesy, National Eye Institute (NEI/NIH)

Cataracts are the most common cause of vision loss and blindness. In the U.S. alone, more than 20 million people over 40 either have a cataract or have had cataract surgery. They develop over a period of years or decades and can be inherited or caused by an injury or caused by damage accumulated over time. The main treatment for cataracts is to remove them through surgery. There are two main surgical procedures used for this, each of them involving removing the lens and replacing it with an artificial substitute. Both of these surgeries are relatively safe and effective.

Aging and the Lens
Aging is the most common cause of cataracts. The cells of the human lens are unique. Made up mostly of water and proteins, the outer layer of the lens is able to protect itself from light damage by lowering its oxygen content, manufacturing protective substances called antioxidants, and maintaining a constant internal circulation of water, ions and metabolites.(1)(2)(3)

Cataracts are the most common cause of vision loss and blindness. In the U.S. alone, more than 20 million people over 40 either have a cataract or have had cataract surgery.

These powerful protective mechanisms can be damaged by traumatic injury and by the effects of aging, particularly in those over 50. Aging can create a buildup in the lens of oxidized proteins and lipids (i.e., fat cells). It can also cause antioxidants to become become depleted, which in time leads to the formation of a barrier between the outer layers and the core of the lens.(4)(5)(6)(7)This is the first step in the development of cataracts, called by the ancient Egyptians, "darkening of the pupil" and "white disease of the eye."(8)

Anatomy of the eye
Courtesy, National Eye Institute (NEI/NIH)


The Different Types of Cataracts
Even among medical authorities, there is no commonly accepted way of classifying cataracts. Some experts classify them by appearance, color intensity or location. Others divide them into infantile (including juvenile), age-related, inherited and systemic.(9)(10) Of these, the age-related type is the most common.

Congenital Cataracts
Congenital cataracts occur in very young children and sometimes run in families. Although quite rare in developed countries, this type has a devastating lifelong impact on vision because they interfere with the normal development of the eye. If left untreated — either by surgery or corrective glasses — congenital cataracts can cause amblyopia (lazy or crossed eyes), squint, nystagmus (fluttering or other involuntary eye movement), and even blindness. Prevention of this kind of cataract is an important component of the World Health Organization's (WHO) international campaign for the elimination of avoidable blindness by the year 2020.

Congenital cataracts are caused by genetic mutations that take place before birth, in the developing fetus.(10)(11)(12) The genes that cause hereditary cataracts have recently been mapped and identified. Increasing knowledge of the genetics underlying cataracts may also help us better understand the role played by environmental and nutritional factors.

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