Typically considered normal vision. The ability to identify a symbol that subtends an angle of 5 minutes of arc, and score 20/20 on the standard Snellen eye chart named after its inventor. It is usually read while standing a distance of 20 feet from it. Visual acuity is traditionally represented as a fraction, with the distance at which the patient is standing being the numerator, and the normal maximum legible viewing distance (“distance” on the chart) being the denominator. So if, at 20 feet, the patient can read the letters on the row marked “20”, the patient has visual acuity of 20/20.
- Twilight sleep
Scopolamine was introduced in 1902. The name comes from the 18th-century Italian naturalist Giovanni Scopoli. Scopolamine is, together with atropine, a component of belladonna which comes from a plant called “deadly nightshade,” once used as a means of poisoning. When scopolamine is given in lower (non-poisonous) doses, it causes drowsiness and amnesia. Scopolamine + morphine […]
One of two children produced in the same pregnancy. Twins can develop from one ovum (egg) or from two ova (eggs). Twins who develop from a single ovum are called monozygotic or identical twins. They have identical genomes. Twins who develop from two ova that are fertilized at the same time are called dizygotic or […]
an involuntary contraction of a group of muscles, also known as a fasciculation.
Involuntary contractions of groups of muscle fibers. Also known as fasciculations. Fasciculations can occur in normal individuals without an associated disease or condition and can also occur as a result of illness, such as muscle cramps, nerve diseases, and metabolism imbalances.
- Two-animal rule
A rule instituted by the US Food and Drug Administration (FDA) for the licensing of agents directed against diseases of low or no incidence. The two-animal rule states that, when agents such as an antibiotic or vaccine are needed for such diseases, these agents may be licensed if they meet two criteria. One criterion is […]