Bifocals - wikipedia Bifocals Bifocals with separate lenses For the bifocal tensor, see Fundamental matrix ( computer vision ). Bifocals are eyeglasses with two distinct optical powers. Bifocals are commonly prescribed to people with presbyopia who also require a correction for myopia, hyperopia, and / or astigmatism. Contents 1 History 2 Problems 3 Future 4 Bifocals in the animal world 5 References 6 Sources 7 External links History Benjamin Franklin is generally credited with the invention of bifocals. Historians have produced some evidence to suggest that others may have come before him in the invention ; however, a correspondence between George Whatley and John Fenno, editor of The Gazette of the United States, suggested that Franklin had indeed invented bifocals, and perhaps 50 years earlier than had been originally thought. However the College of Optometrists concluded : Unless further evidence emerges all we can say for certain is that Franklin was one of the first people to wear split bifocals and this act of wearing them caused his name to be associated with the type from an early date. This no doubt contributed greatly to their popularisation. The evidence implies, however, that when he sought to order lenses of this type the London opticians were already familiar with them. Other members of Franklin 's circle of British friends may have worn them even earlier, from the 1760s, but it is at best uncertain ( and arguably improbable ? ) that split bifocal lenses had a famous gentleman inventor. Since many inventions are developed independently by more than one person, it is possible that the invention of bifocals may have been such a case. John Isaac Hawkins, the inventor of trifocal lenses, coined the term bifocals in 1824 and credited Dr. Franklin. In 1955, Irving Rips of Younger Optics created the first seamless or `` invisible '' bifocal, a precursor to all progressive lenses. Construction Original bifocals were designed with the most convex lenses ( for close viewing ) in the lower half of the frame and the least convex lenses on the upper. Up until the beginning of the 20th century two separate lenses were cut in half and combined together in the rim of the frame. The mounting of two half lenses into a single frame led to a number of early complications and rendered such spectacles quite fragile. A method for fusing the sections of the lenses together was developed by Louis de Wecker at the end of the 19th century and patented by Dr. John L. Borsch, Jr. in 1908. Today most bifocals are created by molding a reading segment into a primary lens and are available with the reading segments in a variety of shapes and sizes. The most popular is the D - segment, 28 mm wide ( citation needed ). While the D - segment bifocal offers superior optics, an increasing number of people opt for progressive bifocal lenses. Problems Bifocals can cause headaches and even dizziness in some users. Acclimation to the small field of view offered by the reading segment of bifocals can take some time, as the user learns to move either the head or the reading material rather than the eyes. Computer monitors are generally placed directly in front of users and can lead to muscle fatigue due to the unusual straight and constant movement of the head. This trouble is mitigated by the use of trifocal lenses or by the use of monofocal lenses for computer users. In an interesting legal case reported in the UK in 1969, the plaintiff 's ability to use bifocals was impaired by accident. Future Research continues in an attempt to eliminate the limited field of vision in current bifocals. New materials and technologies may provide a method which can selectively adjust the optical power of a lens. Researchers have constructed such a lens using a liquid crystal layer sandwiched between two glass substrates. Bifocals in the animal world The aquatic larval stage of the diving beetle Thermonectus marmoratus has, in its principal eyes, two retinas and two distinct focal planes that are substantially separated ( in the manner of bifocals ) to switch their vision from up - close to distance, for easy and efficient capture of their prey, mostly mosquito larvae. This is the first ever recorded use of bifocal technology in the animal world. References Jump up ^ The College of Optometrists. `` The ' Inventor ' of Bifocals ? ''. Archived from the original on 2011 - 06 - 13. Jump up ^ http://www.visionmonday.com/Default.aspx?TabId=211&Parent_content_id=11079&content_id=11095&SkinSrc=%5BL%5DSkins/VM2007/PagePrint&ContainerSrc=%5BL%5DContainers/VM2007/SimpleContainer&dnnprintmode=true Jump up ^ Agarwal, R.K. ( 1984 ), Plaintiff 's ability to use bifocals impaired by accident, The Ophthalmic Optician, 24 ( 25 ), page 898 ( the title of this journal was changed to Optometry Today in 1985, published by the Association of Optometrists, London, England ). Jump up ^ Dawn Fuller ( duly edited ) ( 24 August 2010 ). `` Bug With Bifocals Baffles Biologists ''. ScienceDaily. ScienceDaily LLC. Archived from the original on 25 August 2010. Retrieved 25 August 2010. Sources Letocha, Charles E. ( 1990 ). `` The Invention and Early Manufacture of Bifocals ''. Survey of Ophthalmology. 35 ( 3 ) : 226 -- 235. doi : 10.1016 / 0039 - 6257 ( 90 ) 90092 - A. PMID 2274850. G. Li ; et al. ( April 2006 ). `` Switchable electro - optic diffractive lens with high efficiency for ophthalmic applications ''. Proc. Natl. Acad. Sci. USA. 103 ( 16 ) : 6100 -- 6104. doi : 10.1073 / pnas. 0600850103. PMC 1458838. PMID 16597675. External links Franklin 's letters to Whatley concerning double spectacles. Benjamin Franklin January 6, 1706 -- April 17, 1790 President of Pennsylvania ( 1785 -- 1788 ), Ambassador to France ( 1779 -- 1785 ) Second Continental Congress ( 1775 -- 1776 ) Founding of the United States Join, or Die ( 1754 political cartoon ) Albany Plan of Union Albany Congress Hutchinson Letters Affair Committee of Secret Correspondence Committee of Five Declaration of Independence Model Treaty Franco - American alliance Treaty of Amity and Commerce Treaty of Alliance Staten Island Peace Conference Treaty of Paris, 1783 Delegate, 1787 Constitutional Convention Pennsylvania Provincial Assembly Postmaster General Founding Fathers Inventions, other events Franklin 's electrostatic machine Bifocals Franklin stove Glass armonica Gulf Stream exploration, naming, and chart Lightning rod Kite experiment Pay it forward Associators 111th Infantry Regiment Junto club American Philosophical Society Library Company of Philadelphia Pennsylvania Hospital Academy and College of Philadelphia University of Pennsylvania Philadelphia Contributionship Union Fire Company Early American currency Fugio Cent United States Postal Service President, Pennsylvania Abolition Society Master, Les Neuf Sœurs Other social contributions and studies Gravesite Writings Silence Dogood letters ( 1722 ) A Dissertation on Liberty and Necessity, Pleasure and Pain ( 1725 ) The Busy - Body letters ( 1729 ) Pennsylvania Gazette ( 1729 -- 1790 ) Poor Richard 's Almanack ( 1732 -- 1758 ) The Drinker 's Dictionary ( 1737 ) `` Advice to a Friend on Choosing a Mistress '' ( 1745 ) `` The Speech of Polly Baker '' ( 1747 ) Observations Concerning the Increase of Mankind, Peopling of Countries, etc. ( 1751 ) Experiments and Observations on Electricity ( 1751 ) Birch letters ( 1755 ) The Way to Wealth ( 1758 ) Pennsylvania Chronicle ( 1767 ) Rules by Which a Great Empire May Be Reduced to a Small One ( 1773 ) Proposed alliance with the Iroquois ( 1775 ) A Letter To A Royal Academy ( 1781 ) Remarks Concerning the Savages of North America ( 1784 ) The Morals of Chess ( 1786 ) An Address to the Public ( 1789 ) A Plan for Improving the Condition of the Free Blacks ( 1789 ) The Autobiography of Benjamin Franklin ( 1771 -- 90, pub. 1791 ) Bagatelles and Satires ( pub. 1845 ) Franklin as a journalist Legacy Franklin Court Benjamin Franklin House Benjamin Franklin Institute of Technology Benjamin Franklin National Memorial Franklin Institute Benjamin Franklin Medal Depicted in The Apotheosis of Washington Benjamin Franklin statue, Washington D.C. In popular culture Ben and Me ( 1953 short ) Ben Franklin in Paris ( 1964 musical play ) 1776 ( 1969 musical 1972 film ) Benjamin Franklin ( 1974 miniseries ) Liberty ! ( 1997 documentary series ) Liberty 's Kids ( 2002 animated series ) Benjamin Franklin ( 2002 documentary series ) John Adams ( 2008 miniseries ) Sons of Liberty ( 2015 miniseries ) Sons of Ben ( supporters group for the Philadelphia Union soccer club Refunding Certificate Franklin half dollar One - hundred dollar bill Washington - Franklin stamps other stamps Cities, counties, schools named for Franklin Franklin Field State of Franklin Ships named USS Franklin Ben Franklin effect Related Age of Enlightenment American Enlightenment The New - England Courant The American Museum magazine American Revolution patriots Syng inkstand Family Deborah Read ( wife ) Sarah Franklin Bache ( daughter ) Francis Franklin ( son ) William Franklin ( son ) Richard Bache Jr. ( grandson ) Benjamin F. Bache ( grandson ) Louis F. Bache ( grandson ) William Franklin ( grandson ) Andrew Harwood ( great - grandson ) Alexander Bache ( great - grandson ) Josiah Franklin ( father ) Jane Mecom ( sister ) James Franklin ( brother ) Mary Morrell Folger ( grandmother ) Peter Folger ( grandfather ) Richard Bache ( son - in - law ) Ann Smith Franklin ( sister - in - law ) Retrieved from `` https://en.wikipedia.org/w/index.php?title=Bifocals&oldid=824271523 '' Categories : Corrective lenses Inventions by Benjamin Franklin American inventions Talk Contents About Wikipedia Català Deutsch Español فارسی Français Bahasa Indonesia Nederlands Polski Português Русский Simple English Svenska தமிழ் ไทย Українська Winaray 8 more Edit links This page was last edited on 6 February 2018, at 10 : 18. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. 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Question: who created the first seamless bifocal a precursor to all progressive lenses
Answer: Irving Rips