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.
Multifocal and single vision eyeglass lenses available for presbyopia correction include: 1  Bifocals. Traditional bifocals have a clearly defined zone in the top half of the lens for distance vision and a zone for near vision in the bottom half of the lens. 2  Trifocals.