The earliest evidence of a precise magnifying glass is in Alhazen’s Book of Optics in 1021.
The seven-volume treatise referenced “a magnifying device forming a magnified image.” The Book of Optics transformed the way people understood light and vision and discussed the use of a convex lens to magnify images.
Originally written in Arabic, it was later translated into Latin, which inspired Roger Bacon to study optics and was instrumental to the invention of eyeglasses in 13th century Italy.
Alhazen’s Book of Optics inspired the English philosopher Roger Bacon to compose Opus Majus, a dissertation covering all aspects of natural science including the physiology of eyesight, the anatomy of the eye and brain, reflected vision and refraction, magnifying glasses and corrective lenses.
Corrective lenses bend the light entering the eye to fix refractive errors that cause poor eyesight.
Sometime in the 1280’s, an artisan in Italy placed two magnifying lenses into a frame to be balanced on the bridge of the nose – creating the first modern-day version of eyeglasses.
Corrective lenses reached another milestone in 1604, when Johannes Kepler published The Optical Part of Astronomy. This treatise described the function of the retina and recognized that images are projected inversely by the eye’s lens and then reversed by the brain.
Most notably, he demonstrated that concave lenses correct nearsightedness, and convex lenses correct farsightedness.
The biggest challenge for eyeglasses after their invention was keeping them firmly secured to one’s face. This challenge was remedied in the 1700s with the development of spectacles with double hinged side pieces. The side pieces rest atop each ear and hold the eyeglasses in place –glasses are still made this way today.
Another breakthrough in the development of corrective lenses occurred in the 1780s, when Benjamin Franklin invented the bifocal.
Tired of switching between two pairs of eyeglasses to see up-close and at a distance, Benjamin Franklin devised a way to fit both types of lenses into one frame. He placed the distance lens at the top and the close-up lens at the bottom, successfully combining two types of spectacles into bifocal glasses.
Bifocals were the primary type of glasses for seeing close-up and at a distance until progressive lenses were developed by Varilux in 1959.
Inspired to create a more natural transition between the close-up and distance lenses of the bifocals, Bernard Maitenaz developed multifocal lenses that provide a seamless transition between all viewing distances – progressive lenses.
Close-up of a surgeon’s amputation kit (Courtesy of Thomas Jefferson University Archives & Special Collections, Philadelphia)
By Cristin O’Keefe Aptowicz
Dr. Thomas Dent Mütter’s story is not so surprising if you consider that a man did not need a medical degree to practice medicine in early 19th-century Philadelphia.
In fact, he didn’t even need a license—a practice that Philadelphia would not embrace into the final decade of the 19th century.
Although the tide was changing, the clear truth was that anyone who wanted to put out a shingle and call himself a doctor could do just that.
Basics of modern medicine, such as the infectiousness of diseases, were still under heavy dispute.
Causes of even common diseases were confusing to doctors. Appendicitis was called peritonitis, and its victims were simply left to die.
Bleeding the ill was still a widespread practice. There was no anesthesia – neither general nor local.
If you came to a doctor with a compound fracture, you had only a 50 percent chance of survival.
But Mütter was a different kind of doctor and a different kind of teacher.
By the end of the 1830s, Mütter, young, smart, ambitious, and blessed with extraordinary talents was gaining a reputation as “one of the best of good fellows” in the Philadelphia medical world and not just in the lecture hall.
“He possessed spontaneously, as it were, the art both of making and holding friends,” a fellow doctor would write of him, “a natural amenity of manner and gentleness of character, a manliness of bearing so intermingled with feminine graces that even children were attracted by it, and a love of approbation that induced him to do what he could to please others.”