How Glasses Have Been Used To Correct Visual Problems
Unbelievably, in the old days, a person’s reading eyeglasses’ strength was only a function of that person’s age. Hence a man of about 30 would be given lenses with 2 degrees of strength and a person of about 70, given, roughly, 4 degrees. It wasn’t until the middle of the 19th century that eyeglasses started to be issued by people who knew some basics about optics.
It is remarkable that in our present scientific age, when the appropriate corrective lenses can be prescribed on the basis of precise measurement of refractive errors, some people still choose their own reading specs at the chemist’s shop.
Astigmatic correction was not generally available until late in the nineteenth century, despite Airy’s cylindrical correcting lens (1827) and Donders’ comprehensive book on refraction (1864). A great many problems have been solved due to necessity. Benjamin Franklin – yes THE Benjamin Franklin, needed to devise bifocal lenses for himself and so he split apart the lenses in his reading and distance eyeglasses and just stuck them together – Hey Presto: Bifocals were invented.
In the early 1800s Hawkins tried to launch trifocal lenses to the spectacle wearing population. Successful multifocal lenses, which have smoothly increasing power over the lower half of the lens, with no visible segment line, were brought in during the 1960s. Sadly, these innovative lenses didn’t work well in practice as the range of clear vision was too small to make their use practical.
It may be that multifocal lenses do have a role in patients with emerging multifocal lenses, as they may be better positions to tolerate the increasing strengths.
You may find the history of specs interesting as I do. I would advise you to really study spectacles and their beginnings to help you better appreciate what a wonderful device they truly are. If you are intent on purchasing your glasses online, then please make sure that you get them from a proplerly trained source.