This is a secondary lens built into the bottom of glasses to help with reading. Though there is some historical debate, most people credit Benjamin Franklin as the inventor of the modern bifocal. There are many styles of modern bifocals. Progressive lenses are bifocals, without a visible line, that progress to a stronger view the further down the glass you look.

Dr. Timothy Root is a practicing ophthalmologist and cataract surgeon in Daytona Beach, Florida. His books, video lectures, and training resources can be found at:


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