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A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
Congestive heart failure is a serious disorder that carries a reduced life expectancy. Heart failure is usually a chronic illness, and it may worsen with infection or other physical stressors.
The eye muscles are the most active muscles in the whole body. The external muscles that move the eyes are the strongest muscles in the human body for the job they have to do. They are 100 times more powerful than they need to be.
Asthma occurs in one in 11 children and in one in 12 adults. African Americans and Latinos have a higher risk for developing asthma than other groups.
Nitroglycerin is used to alleviate various heart-related conditions, and it is also the chief component of dynamite (but mixed in a solid clay base to stabilize it).
![Osteoporosis. (a) A section through normal spongy bone. (b) A section through a bone with osteoporos](https://biology-forums.com/gallery/47/medium_14755_11_11_12_7_28_46_100741243.jpeg)
![Herniated disk. A herniated disk is a protrusion of the disk’s gelatinous center, called the nucleus](https://biology-forums.com/gallery/47/medium_14755_11_11_12_7_28_47_10077486.jpeg)