In a normal, healthy eye (at left), the lens is surrounded by a capsule and situated just behind the iris. If this lens grows cloudy and impairs vision, it can be replaced by an artificial intraocular lens. The plastic lens …
Keratoconus: Cone-shaped corneas
In keratoconus the corneas become cone-shaped, causing nearsightedness and visual distortion. The condition affects more women than men and usually affects both corneas, though to different degrees. Onset often begins around puberty and progresses slowly over five to twelve years. …
Radial keratotomy
Surgeons improve nearsighted vision by changing the shape of the eyeball. Nearsighted vision results when an elongated eyeball makes images focus in front of the retina, instead of on the retina surface. Radial keratotomy corrects the elongation through surgery. Four …
Glaucoma
The front of the eye is filled with a fluid called aqueous humor. It is produced inside the eye by the cilliary body and flows outward at a steady rate. Normally the fluid passes through the iris and into a …
Gallstones
The liver produces a liquid called bile that aids in the digestion of fats in the small intestine. Bile collects in the gallbladder, a small sac beneath the liver, where it is stored and concentrated. When bile becomes chemically imbalanced, …
Hot flash
About 75 percent of women experience hot flashes, which lead about 10 to 20 percent of women to seek professional help. Most hot flashes occur during the first two years after menopause and lessen thereafter. Of women with hot flashes, …
Ulcers, peptic
Peptic ulcers The stomach and intestine digest food using powerful acids and enzymes. The tissue lining the digestive tract avoids digesting itself by secreting a protective layer of mucus, regulating acidity and repairing itself. When these protections break down, ulcers …
Vertigo
Benign positional vertigo The sense of motion comes from the inner ear, a series of fluid-filled chambers. Within each of three semicircular canals, a jelly-like mass known as the cupula contains hair cells connected to nerve fibers. As the head …
Weight charts for men and women
Measuring weight Obesity increases a person’s chances of serious illness such as diabetes mellitus and heart disease. A person is considered obese if his or her weight is 20 percent or more over the maximum desirable weight for his or …
Osteoporosis prevention
Osteoporosis prevention Bones gradually lose density with age, inactivity or (for astronauts) prolonged weightlessness. Osteoporosis occurs when tissues within the bones becomes thin, brittle, and can no longer provide structural support against gravity. Fractures then become common. Women are more …