Markup View

Author: 69BookWorM69

Dec 13th 2011 at 9:43:01 AM

You're missing '''presbyopia''', in which the lens of the eye loses flexibility and cannot focus. This is associated with middle age (usual onset around age 45). This leads to specific, aging-related glasses and behaviours with glasses. Some people (who do not need glasses for distance vision) may wear distictive half-glasses or reading glasses for close work. Other people (who are nearsighted) may simply take off their distance glasses to read. Often people who use glasses for presbyopia are shown putting the glasses on their heads (often men), or wearing them on a chain round the neck (usually women).

The glasses themselves can have bifocal or trifocal lenses. Earlier versions of this technology had visible lines in the lenses; aside from producing areas of abrupt focal change (which could be disorienting to the wearer), the lines themselves were a visible marker of the wearer's age. Modern lenses, including contact lenses, lack the abrupt transitions and the tell-tale lines.

Surgical techniques using lasers are a way to avoid corrective lenses of any kind, just as with other conditions. Some people choose to correct one eye for near and one eye for far vision. This is called "monovision," and it too eliminates the need for bifocals or reading glasses, but it can affect depth perception.