When people think about inventions of medical gadgets, lenses and spectacles hardly come to their mind. Its widespread use is perhaps the reason it is not considered as anything innovative. It has been there for such a long time that even history of past few centuries does not have any reference about it. Only when one studies an entire decade of past from now that bifocal lenses and other ophthalmic equipment can be learnt about. Besides, the usefulness of an equipment is most realised when it is unavailable, which has never been the case with spectacles due to sufficient supply of it.
As far as history is concerned, the innovation of bifocal lenses is associated with Benjamin Franklin, former statesman of the US. The evidence behind his association with the innovation is the overwhelming price of 18Franks that he paid to Sykes, English optician situated in France, for a pair of spectacles in 1779, when Franklin was serving as a US ambassador to France. Besides, in one of his letters written in 1784 to George Whatley, Franklin has expressed contentment towards double spectacles that made his eyes equally useful, according to him, as they were earlier. These statements have been supposed to suggest that Franklin used something extraordinary that was ordered by him too.
However, researches reveal evidences that The Dollonds had already been manufacturing same or similar kinds of spectacles by that time. However, commercial prospects of it could never be perceived by them. Thus, their production remained only bespoke service. In this context, Franklin can be considered to have popularised the ophthalmic equipment but not as its inventor.
The fact can further be supported by a letter written by John Fenno, editor of an American newspaper, to his wife in 1789. In the letter, he mentioned about his meeting with the statesman in which Franklin mentioned his dependence upon spectacles. Fenno was told by Franklin that he wore spectacles fro past 50years but had the bifocal lenses only in 1780, which is more than a decade later than the earliest experiment done for the cause.
However, this cannot be stated as a hard fact whether Franklin did or did not innovated the bifocal spectacles. The fact that he suffered with hyperopia, which made him dependent upon spectacles since 1730, does leave the scope to consider that Franklin might have used bifocal spectacles or experimented with earlier than its popularisation. Besides, his enthusiasm for ophthalmic equipment is known and confirmed. He had promoted various ophthalmic aides in the US and had even imported various vision aides for himself. However, he had been depicted with bifocal spectacles in one of the portrait made by Charles Peale in 1785 while the equipment gained popularity among public during the decade of 1790s.
Lens has been in use since 300BC. However, people recognised it as an ophthalmic aide not before 1280, when it was started to be used to aide far-sight. It was only in 1570 that lenses were found to support near-sight too.