E-commerce is a major factor in the U.S. economy because it assists companies with many levels of current business transactions, as well as creating new online business opportunities that are global in nature.
Eye Health. A bifocal is a lens that has two focal points, usually one lens for viewing distant objects, and one lens for viewing close objects. A bifocal is also known as a multi-focal lens. Ben Franklin is credited as the inventor of the original bifocal lens. Presbyopia.
bifocals, page 16 Â© W. F. Long, 1992A double segment is has an additional add at the top of the lens. It is anoccupational lens for painters, pilots, and the like.The top segment may be obtained in any power. The near correction can behad in a bifocal or trifocal.