Presbyopia
The loss of the eye’s ability to change focus to see near objects. The reasons for this loss of the power of accommodation are not yet fully known. It is conventionally said to be due to the lens becoming less elastic with time.
Presbyopia is associated with aging. It occurs in everyone. The first sign is often the need to hold reading material farther away.
The lens of the eye and the muscle that surrounds it are like atomic clocks, slowly ticking with such precision that a person’s age can be determined by measuring their ability to focus close up.
Children can normally focus on objects an inch or so (a few centimeters) from their eyes. They lose that ability as teenagers. By age 45 or so, when the eyes can focus no closer than a yard (a meter) or two away, almost everyone needs glasses to read a newspaper or thread a needle.
The word “presbyopia” comes from the Greek for “elderly vision.”
Read Also:
- Prescription
A physician’s order for the preparation and administration of a drug or device for a patient. A prescription has several parts. They include the superscription or heading with the symbol “R” or “Rx”, which stands for the word recipe (meaning, in Latin, to take); the inscription, which contains the names and quantities of the ingredients; […]
- Prescription drug
A drug requiring a prescription, as opposed to an over-the-counter drug, which can be purchased without one.
- Presentation, breech
Birth in which the buttocks present before the head.
- Presentation, footling
There are single-footling or double-footling presentations depending upon whether the presenting part of the baby at delivery is just one foot or both feet.
- Presentation, vertex
In a vertex presentation, the top of the baby’s head comes first at delivery. The vertex here refers specifically to the top of the head The word “vertex” in Latin means a “whirlpool, whirlwind.” Why “top of the head”? Because the hairs on the top of the head often form a whorl, a whirl-like pattern.