The History of Ophthalmology
Part 2: The Middle Ages: Spectacles
Latin texts which survive from the 14th century mention using a “reading stone” to help old people to read – a magnifying glass rather than spectacles. Most of the reading was done in monasteries and a Dominican monk in Pisa, one Fra Alessandro da Spina, is credited with re-inventing eye glasses, having learned to do it from someone whose name is lost.
Alternatively, some say that Marco Polo may have brought the idea back after traveling the Silk Road to China in 1270; so maybe we should thank the Chinese. However, the Chinese claim that eye glasses were invented in the 11th century in Arabia. Perhaps, since spectacles were a much-needed amenity in the world, they were invented by several people around this time.
Spectacles came into high fashion in the 14th century and people wore them regardless of need. They were such a hit that artists gave them to biblical characters in their paintings. To obtain a pair, one waited for an itinerant peddler to come to town, selling spectacles along with potions and amulets etc. In 1452, printing presses were invented, so that books became more readily available, which increased demand for spectacles.
Glasses did not yet have any ear pieces, but were balanced on the nose or held in front of the eyes. Nor were they rigid in design, but riveted together. That made it important to remain still while balancing them on the nose, as a small movement could send them tumbling.
More prosperous people had their glasses framed in gold or silver and the less prosperous used frames of bone, horn, wood or leather.
In the early 17th century, rigid bridges were designed, either curved or straight, which made wearing these glasses more stable; but ear pieces were still absent. There was also a style featuring a single lens with a vertical stem. These were presumably for short-term use, being held up for the person to peer through one eye at some important small item. (Later, monocles were used in this fashion, attached to a chain and kept in a man’s waistcoat pocket when not in use.) Another style was folding glasses.
Telescopes and Eyes
Basic to designing spectacles is some understanding of optics – the study of how light behaves and how it relates to matter (meaning solid substances such as our eyes). Early interest in optics related to mathematics, astronomy and telescopes as well as to how our eyes work.
How people see the sky is a two-sided issue involving:
- How the eye works; and
- How a telescope could be made to work.
The 16th and 17th centuries saw intense exploration of both the human eye and Earth’s sky, and in the 17th century people finally made the difficult switch from regarding Earth as the center of the universe to regarding the Sun in that position. Most of us have heard of the central figures, even if we are a bit fuzzy about exactly what they accomplished: Tycho Brahe, Copernicus, Galileo, Kepler, and Sir Isaac Newton.
Of those, Kepler (1571 to 1630) and Sir Isaac Newton (1643 to 1727) did the most work in optics. But there were also less famous scholars, such as the Jesuit priest Christophe Scheiner (1575–1650), whose 1619 tome on the human eye laid out eye anatomy, described how light is refracted by the eye, and presented step-by-step reasoning to show that the retina is the “seat of vision”.
Some Optical Terms
Optical power is another term for refractive power – the ability of any lens to refract (bend) light, either converging it to a focal point, or scattering it.
A related term is focal length. A lens (whether in the eye or elsewhere) with high optical power has a short focal length – it can bring light to a focus in a short distance. A lens with low optical power has a longer focal length, as it refracts light at less acute angles.
Since the eyeball has a fixed size, the retina is a fixed distance away from the cornea and lens, both of which refract light.
- If the cornea and lens between them refract incoming light so strongly that it focuses before it arrives at the retina, that eye is myopic.
- When they refract light too weakly, so that it would focus behind the retina if it could travel through that tissue, that eye is hyperopic.
So an eye’s refractive power is always considered in relation to its length front to back.
Vision Problems Corrected by Early Spectacles
At first only convex lenses were used, for those who had cataracts removed, and to correct “old sight” (presbyopia) and “old sight in young people” (hyperopia). In the 16th century, concave lenses were used for correcting “short sight”. However, there was still no way to determine anyone’s exact vision needs – no way to examine the eye closely enough to write a prescription.
Contemporary oculists were scornful of glasses, not “seeing” how an eye could see better with something stuck in front of it. This attitude continued into the 19th century, its proponents insisting that glasses would deform the eyes or cause “old sight” or “short sight”. But there were also oculists who got on board, and in London they belonged to the Worshipful Company of Spectacle Makers, working on establishing high standards.
In the early 18th century, a London optician designed a pair of glasses with iron frames and ear pieces – temple spectacles. Around this time also, Ben Franklin, who wore glasses himself, designed bifocals.
Also in the 18th century, the first attempts were made to surgically open the eye to remove the cataract lens, but the success was mixed. Handel, the court musician in London and composer of the famous Messiah we hear so often at Christmas, had this procedure done towards the end of his life, but it was not successful and blinded him.
In the 18th century, spectacles were considered so valuable that they were bequeathed separately in the wills of prosperous people. The widespread itching to get rid of them and see clearly without such an annoying appendage had not occurred yet.
History of Ophthalmology Part 1: The Ancient World
History of Ophthalmology Part 3: Anesthesia and Infection
History of Ophthalmology Part 4: The Nineteenth Century: Seeing the Eye
History of Ophthalmology Part 5: The Twentieth Century: Swift Progress
History of Ophthalmology Part 6: What is a Laser?
History of Ophthalmology Part 7: Leading up to LASIK
History of Ophthalmology Part 8:LASIK Into the Twenty-First Century