|
|
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.
Interferon was scarce and expensive until 1980, when the interferon gene was inserted into bacteria using recombinant DNA technology, allowing for mass cultivation and purification from bacterial cultures.
Fewer than 10% of babies are born on their exact due dates, 50% are born within 1 week of the due date, and 90% are born within 2 weeks of the date.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.