What do you know about your glasses?

Someone commented on my new glasses recently, placing more value on them as a fashion statement than on what they were for. Having less-than-perfect vision isn’t as uncommon as you may think, and the need for eyeglasses is varied - some need help from an early age, others can’t see far, near, or both, or have genetic problems that make seeing clearly difficult from one or both eyes.

We take it for granted that a visit to an optician is a simple fix - put your face into some sort of machine, they look at your eyes, maybe watch a few spots move about, take a few measurements, and hey presto, vision restored with lenses in frames of your choice.

Centuries of Corrective Lenses

Since as early as 60 AD, people have been using vision-correcting tools to help them see. One Roman philosopher used a glass globe of water to magnify text, while Emperor Nero used a magnifying emerald to see gladiator fights. The monks of 10th-century Europe made the next big leap forward, by using polished domes of transparent quartz called ‘reading stones’ to help them with their illuminated calligraphy work.

Several centuries passed before early spectacles were used, and a Florentinian named Salvino D’armati is often credited for it.

Glasses through the ages

When spectacles were first invented, they could only be made out of expensive materials such as crystal, making them a status symbol for the wealthy, but with the skyrocketing literacy rates in Europe, demand for affordable reading glasses increased. Glass started being used to make the lenses, a much cheaper option to crystal.

But glasses still had a long way to go. They perched on the nose or had to be held with a handle, and glass blowers who made the lenses weren’t able to help people with different sight needs. Glasses finally became ‘hands-free’ in the 1700s when the temples – or arms - were added. Then hinges were added so that glasses could be folded and stored more compactly, and over time, eye doctors got better at tailoring lenses to patients’ individual needs.

Today’s lenses

Modern-day spectacles are made to a prescription using a mixture of science and technology. Different prescriptions and frame sizes means every lens has a different curvature, so firstly, the optical prescription of the lenses is entered onto a computer which then prints all information required in the manufacturing process of the lenses.

Lens blanks are selected and are then marked at the ‘optical centre’ – the exact, clearest, centre point to be looked through, using a lensometer/focimeter. High-index polymers are used for higher prescriptions, to make them thinner, and these are highly reflective so need an ’anti-reflective’ layer to improve vision and aesthetics. The lenses are then covered in a special layer to protect them during the grinding process, and a generator or grinding machine curves the back or front and back on higher prescriptions, to make the lenses less thick and to reduce distortion. The optical centre is moved in the process of cutting the lenses to sit directly in front of the pupils, which varies from person to person.

Coatings

After they are ground, they can be coated with any treatments or tints if desired. Common treatments include ultra-violet tints, scratch-resistant and reactive coatings such as a photochromic coating, which causes the lens to darken when activated by UV light. They are then polished, bevelled and sterilised, and finally, they will then be fitted and assembled into the frame by hand.

Lenses can now made from glass, polyethylene, Trivex, polycarbonate or high-index polymers. Materials for frames are plastic, metal or flexible metal, and are lighter, more versatile and easier to work with. The manufacturing process may need human hands at specific points, but much more is now automated, meaning faster manufacturing.

Cost

When you buy glasses from a traditional retailer, you're not just paying for the frame and lenses; you're also paying to cover the retailer's hefty outsourcing costs, which usually include detailed manufacturing, licensing fees, warehousing, and more.

There’s more to making glasses than meets the eye!

Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan