How Glasses Have Been Used To Correct Visual Problems
The strength of reading specs was originally based on the patient’s age. A middle aged man would be issued glasses with a strength of 2 degrees and a person of more advanced years offered a 4 degrees of strength pair of specs. Around the middle of the 1800s eyeglasses were being sold by knowledgeable students of optics.
There are still a few luddites who ignore the technological advances of the 21st century and get their reading specs from the local 7-11.
Despite the works from Airy on the cylindrical correcting lens in the early 1800’s and Donders brilliant work concerning refraction later that century, it was only in the late 19th century that people were starting to correct their patient’s astigmatisms. Many a solution to a problem has been borne out of 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.
Hawkins introduced trifocal lenses in 1826. It was only in the 1960’s that manufacturers produced smoothly increasing powers in a better range of multifocal lenses. Sadly, these innovative lenses didn’t work well in practice as the range of clear vision was too small to make their use practical.
|If presbyopia is just emerging, then multifocal lenses may have a role, whilst the person learns to tolerate the increasing strengths.
You may find the history of specs interesting as I do. I would advise you to really study specs and their beginnings to help you better appreciate what a wonderful device they truly are. If you are intent on purchasing your reading glasses online, then please make sure that you get them from a proplerly trained source.
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Tags: eyeglasses, specs, spectacles
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