The BALL REPORTS

News As I Like It, Not As You See It:

Lens Designs

April 23, 2008

		Single vision
		A single vision lens consists of a single sphere of appropriate radius providing correction for near vision only. Distance vision through the lens is blurred and there is no specific correction for intermediate vision.
		Bifocal lenses
		In a bifocal lens, the distance vision sphere is placed above the near vision sphere and linked by a single "step" made manifest by a visible segment line.
		Trifocal lenses
		In a trifocal lens, a third sphere is added between the distance and near vision spheres to produce an intermediate vision power. This creates two segment lines.
		Progressive lenses
		In a progressive lens, an uninterrupted series of curves links distance vision, intermediate vision, and near vision with no visible separation. This creates a smooth progression of power from the distance vision area at the top of the lens, through an intermediate vision area in the middle, to the near vision area at the bottom of the lens. Since they have no abrupt change of power and no noticeable segment lines, progressive lenses are sometimes referred to as "no-line bifocals." But improved cosmetics are just on of their benefits.

 

Your humble Ace Reporter

Bob

Prior | Tell us what you think | Next

Add to Your Social Bookmarks: Del.icio.us Digg Furl Reddit Simpy Spurl Y! MyWeb - Netscape - StumbleUpon StumbleUpon