How the invention of the lens helped us see the world more clearly

The glass lens has allowed us to correct our vision, see the furthest objects in the sky, and the smallest objects on the Earth. Oh, and there's photography and film as well.

A 'spectacular' history that has helped billions. But billions more still need affordable access.

Where would we be without eyeglasses, telescopes or microscopes? (Adam Killick)

Glass lenses have been a boon for myopes and presbyopes around the world, but the evolution of this technology also offers insight into social history.

Neil Handley is the museum curator at the British Optical Association Museum and world-renowned expert in the history of eyeglasses. He says that pinning down the date someone made the first actual set of corrective lenses worn is a difficult thing to do.

"In the early days, spectacles were like a badge of literacy," said Handley. The earliest spectacles were for close work, particularly for reading and sedentary activity.

Neil Handley is the Museum Curator at the British Optical Association Museum. (Edward Moss)

As literacy rates rose, the demand for corrective lenses and the demand to correct a variety of vision problems grew. 

With the discovery of astigmatism, bifocal lenses and the range of different things you could do with spectacle lenses increased, the market grew and it then became possible for an optician to specialize, for example, in spectacles.

"Until the 19th century, an optician was just somebody who's learned in optics and they might be somebody who sold microscopes or telescopes. Some of them were involved in the early days of photography, and you'd go to an optician to buy a camera. So it's in much more recent times that you have the spectacle specialist who's concerned only with providing spectacles to customers, and then as an extra service, testing the eyesight of the customers as well," Handley told Spark host Nora Young.

He says this led to the medicalization of opticians and the growth of modern optometry.

The availability of cheap materials, particularly steel, which came in the mid 19th century, helped pave the way for the mass production of eyeglasses. Handley also credits the social developments in various parts of the world where there were good supplies of running water, necessary to run the machinery to mass produce spectacles. 

Lenses have not only helped us see better, but they've also shed light on deeper understanding of the world around us. The development of corrective lenses influenced the development of telescopes and microscopes, among other things.

Getting glasses to the Global South

While glasses have come a long way and are now more accessible, there are still billions of people in need of them — but without the means or resources to get them. That's a challenge atomic physicist Joshua Silver has taken up.

By some estimates, there are three billion people in the world who need corrective glasses but don't have them. That's largely because of a lack of eyecare physicians or the specialized equipment needed to make the lenses.

"People tend to think that if they need glasses, they have to have an eye test. So you have to have people who can test eyes and tell you what you need in terms of your prescription. And in the so-called developed world, you have plenty of opticians, maybe one per 5000 or 10,000 people. There are areas of the world, some countries in Sub-Saharan Africa, where you typically have one optician for maybe a million people," Silver told Young.

Atomic physicist and Oxford professor Joshua Silver. (Centre for Vision in the Developing World)

He says there's often a conflation of two very different things — assessing eye health and vision. "Our peer reviewed published research has shown that you do not need an optician to get clear vision."

"So if your mindset is that you need an eye test to get glasses, you do a quick physicists' order-of-magnitude estimate, for a country where you have one optician for a million people, and you will wait about 200 years to see the optician on the average, so it doesn't work."

Silver, a physics professor at the University of Oxford, pioneered a solution called 'adaptive' glasses, which cost about a dollar a pair. The technology allows users to figure out their own prescription in places with no optometrists.

The fluid-filled membrane lenses allow eyeglass wearers to adjust their prescription to see clearly over time. By adding or removing liquid inside, they can change the curvature of the lens and its focusing power.

Silver says lenses aren't the solid fixed object that people believe them to be. 

"Most people in fact, if you give them a pair of spectacles with adaptive lenses in them, which are easy to adjust the power and they will be able to accurately correct their refractive error," he said.

The eye-brain adaptive optical system has evolved so that people can tell whether their vision is clear. "In other words, the brain interprets the image on the retina and tells you whether it's sharply focused or not."

He says what works best is starting with what in the optician's world is called "fogging." "You start with the plus power, so things look blurry. And then you slowly reduce that power until you get clear vision, then you stop," said Silver.

The total number of these adaptive glasses that have been distributed in over 20 countries is around 100,000.

Through his organization, the Centre for Vision in the Developing World, Silver is working to produce and distribute these adaptive glasses to the people who need it most, but challenges remain — including shortcomings in addressing conditions, like astigmatism.

Written by Adam Killick. Produced by Adam Killick, Nora Young, and Samraweet Yohannes.