Cataract

Cataract is the single leading cause of blindness worldwide. It is caused by the opacification (clouding) of the crystalline lens within the eye. Luckily, the disorder can usually be corrected by surgical removal of the clouded lens and, if possible, replacement of the old lens with a synthetic one in order to restore proper sight.

Cataract can be classified by its cause, stage, or anatomical classification. While age-related cataract is most frequently observed, other common forms of cataract include congenital, traumatic, or complicated. Congenital cataracts are present from birth or develop very early in life, necessitating early removal of the clouded lens in order to allow for proper development of the infant's sensitive visual system. Eye trauma from accidents or injuries can also cause cataracts to form in the eye. Complicated cataracts develop when other eye diseases—such as glaucoma, retinitis pigmentosa, retinal detachment, or uveitis—affect the physiology of the lens.

Cataract classifications based on stage include immature, mature, hypermature, and morgagnian cataract. While immature cataracts still have some transparent protein left, mature cataracts are often easily recognizable because all proteins have become opaque. Hypermature cataracts progress so far that their proteins become liquid; if the nucleus (center) of the lens floats freely in the lens capsule's “bag,” the cataract is classified as morgagnian and should be removed immediately.

Nuclear cataracts begin at the center of the lens; the cloudiness grows from the center and negatively affects vision.

Finally, cataracts may also be classified by their anatomy. Nuclear cataracts begin at the center of the lens; as the cataract progresses, the cloudiness grows from the center and changes the lens color, negatively affecting vision. Cortical cataracts are whitish opacities that begin on the outer edges of the lens and gradually grow to the center, interfering with proper lens function. Subcapsular cataracts develop in the back of the lens and quickly begin to block light from passing through the lens onto the retina.

There are several key risk factors for cataract; while some of these are unavoidable, others are important to note because they may help reduce the huge global backlog of people in need of cataract surgery. The biggest risk factor for cataract is age; worldwide, at least some opacification of the lens occurs in 50 percent of people over age 60 and 100 percent of people over age

80. Studies reveal that females are slightly more likely to develop cataract than males. Diabetes and other health complications can not only cause eye diseases such as diabetic retinopathy, but may also increase the risk of developing cataract.

The two most easily preventable risk factors for cataract are ultraviolet (UV) light exposure and smoking. Harmful UV radiation from the sun damages the lens and expedites the process of opacification. It is strongly recommended that all people, regardless of age, wear UV-resistant sunglasses outside during bright days. However, due to poverty and lack of education in many countries, sunglasses are rarely, if ever, used by most of the population. Another preventable but often ignored risk factor for cataract is smoking. Smoking releases permanently damaging free radicals within the body, increasing the risk of cataract formation.

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