Glasses Lenses Through the Centuries
The earliest example of someone using a tool to assist with vision (that we know of) is Roman philosopher Seneca.
He used a glass globe of water to magnify text when he was reading. Around the same time (60 AD), Emperor Nero was using an emerald to see gladiator fights better. Glasses have obviously come a long way since then, but let’s take a look at some of the major developments that eventually led to the precise, durable, lightweight eyewear we enjoy today.
The Evolution of Corrective Lens Materials
The first example of actual manufactured lenses designed to help with reading was in 10th century Europe, where monks made polished domes of transparent quartz called “reading stones” to help them create beautiful illuminated calligraphy. It took a couple more centuries before it occurred to anyone to fashion these stones into spectacles. The man most often credited for this is Salvino D’armati of Florence.
After these early glasses hit the scene, they became a major status symbol, made only out of very expensive materials like crystal. Over time, the preference for glass grew, and demand for affordable glasses shot up after the printing press was invented in 1440 and literacy rates were higher than they had ever been.
Modern Lenses
These days, we mostly make our glasses out of plastic, but some glasses are still made of actual glass, even all these centuries after D’armati. Glass lenses are affordable, highly resistant to scratching, and create minimal distortion of colors, but they are heavy, fragile, and (depending on prescription strength) can be very thick.
Plastic lenses are much more versatile. They are lightweight, durable, and can have a much thinner profile than glass, depending on their index. Higher index plastic lenses can be made thinner, though they will be more expensive.
There are also polycarbonate lenses, which are ideal for kids and athletes because they are extremely hard to break. They’re thin and light as well, which is good for strong prescriptions. A disadvantage is that they do cause some color distortion. They also aren’t very scratch-resistant, but that can be fixed with special coatings. Which brings us to…
Beyond the Lens Itself: Lens Coatings
One thing that is definitely unique to modern glasses is the special coatings we can apply to them. Soft lenses can be protected with scratch-resistant coatings. There are also UV-blocking coatings to protect your eyes from harmful UV rays, and anti-reflective coatings to eliminate glare and reduce eye strain.