Seeing through Glass

If it weren’t for eyeglasses, many people would be constantly squinting to see clearly. Today, there are eyeglasses and contact lenses to help with almost every kind of vision issue. Some experts claim that eyeglasses are the fifth-most valuable invention, only after discoveries as important as fire and the wheel.

Eyeglasses have not only helped many people see better in everyday life, but they have also made it possible for more people to read, write, and share information. How did the invention come about? This incredible invention had its start centuries ago, and for a while, the craft of making eyeglasses was a closely guarded secret.

A Need to See

History shows that people lamented the problem of poor vision for thousands of years. Around 100 BCE, famous Roman speaker Cicero complained about needing to have others read his speeches out loud. About 150 years later, Roman emperor Nero peered through a clear green stone as he watched events in hopes that this action would refresh his eyes.

Finding a Solution

Almost 1,000 years passed before someone proposed a more substantial idea to improve vision. In 1021, Arab scientist Ibn al-Haytham completed the Book of Optics. This book described the eye and possible solutions for vision issues. Ibn al-Haytham thought that looking through smoothed-glass lenses made of parts of a glass sphere might be helpful.

The Book of Optics was translated into Latin in 1240 and became popular among monks in Italy. Some of these monks utilized al-Haytham’s ideas. They developed a half-sphere lens made of rock crystal and quartz. People could put this “reading stone” on top of writings, which would magnify the words. Older monks appreciated seeing the larger words. The reading stones allowed the monks to continue reading even when their vision began to deteriorate.

A Secret Craft

People began making glass as early as the sixth century. However, glassmaking was a difficult process. It involved heating specific materials until they melted and then using tools to shape the hot liquid materials. When the materials cooled, the shapes became hard. Glass would often break as it was being made, and if it didn’t, it was sometimes thick and bumpy.

During the 1200s, some craftspeople on the island of Murano in Venice, Italy, invented smooth glass. These glassmakers were known as the “cristalleri.”

The smooth glass made by the cristalleri was very popular. Suddenly, people could see much more clearly through windows. But the leaders of Venice were not about to let others know how this amazing glass was made. They protected the secrets of the glassmaking process carefully. In fact, the cristalleri were not even allowed to leave the island.

Rivet Glasses

By the end of the thirteenth century, the cristalleri had fashioned the first pair of eyeglasses. First, they cut two round pieces of glass. Each piece, called a lens, was only a bit larger than an inch in diameter. Each lens was convex, meaning that it was rounded out like part of a bubble. The convex shape helped to magnify things. This made it easier for people to see words when they read.

The cristalleri encased each lens in a wooden frame with two long, thin rods. The two rods were placed at an angle to each other. They were connected by a metal rivet. The angle made a space for the nose, so people could hold the “rivet glasses” in front of their eyes without the nose getting in the way.

Rivet glasses did not have what are now known as “temples,” or thin rods that rest the glasses on the ears. People had to hold them in place. Still, many people wanted to use rivet glasses. These eyeglasses provided more help for people to see than had ever existed before.

Although the cristalleri tried to keep their methods a secret, their ideas eventually got out. Leaders in Venice passed a law that eyeglasses could only be made by the cristalleri. However, over the next few hundred years, the process found its way across Europe.

Better Glasses

As time went by, people came up with new ideas for how to place the glasses on the bridge of the nose. The triangle shape created by the rods connected by a rivet was uncomfortable. Rivet Glasses were replaced with frames that fit over the nose. People also added temples to help the glasses rest on the ears.

Today, eyeglasses have many kinds of comfortable, light frames. They are made to fit well over noses and ears. And more importantly, the glass used in eyeglasses is shaped specifically for each eye. Eyeglass makers can use exactly the right curves to help people see perfectly. Now that is an invention worth celebrating!