How do contact lenses work?

I have needed glasses since the tender age of eight. When I was 16, I opted for contact lenses because when I told my optician that I was not wearing my glasses all the time she seemed disappointed in me. Don’t you just hate it when you disappoint your optician?!

So now, sometimes I wear lenses and sometimes I wear glasses, but how contact lenses actually work?

They do exactly the same thing that glasses do, which is change the direction of light waves to focus the light onto the retina.

When someone is short-sighted, like me, the light rays focus too early in their eye, before the retina. Glasses and contact lenses diverge the light so that it focuses right on the retina and makes things clearer. If someone is longsighted, the opposite is true (light rays focus behind the retina, so glasses converge the light so it focuses on the right place). See lovely diagrams below.


No contact lens
With contact lens

Contact lenses can be nice and small because they are much closer to the eye than glasses. The optic zone on a contact lens is only about the size of the pupil, the rest of the lens is just there so it can fit on the eye.

Then I was wondering what contact lenses were like when they were first made. Right now, they are made of silicone hydrogel. They are also pretty cheap, disposable and can be worn for a whole day. They surely did not start off that way.

I was quite surprised to learn that Leonardo Da Vinci thought of the idea of them all the way back in 1508. They weren’t really like the lenses we have today. They were water-filled glass hemispheres which fitted over a person’s eye. Sounds less practical than glasses really. Then, in 1636, Rene Descartes (of I think, therefore I am fame), made a sketch of some lenses which were hollow glass tubes filled with water and placed directly on the cornea, which sounds horrible.

The first eye covering that people could actually wear and see through was made by a German glassblower called F E Muller in 1887. Before this, coverings that improved vision were too uncomfortable and coverings that were comfortable could not be seen through! The first successful contact lens was made in 1888 by Adolf Gaston Eugen Fick, these lenses laid around the cornea of the eye and could be worn for a few hours at a time.

In the 1930s, Plexiglas was invented, so in 1936 lenses could be made thinner and lighter. In 1949 lenses were made which only covered the cornea and not the whole eye, this increased the comfort even more and gave contact lenses more appeal.  However, they were still very expensive, people could even take out insurance to replace them!  They were also still made out of Plexiglas, which does not let in much oxygen. This could cause some bad side effects.

In the 1970s, research started on rigid gas permeable polymers (RGPs), as well as soft contact lenses, which could both let oxygen into the eye. FGPs were the most popular up until the 1990s when soft contact lenses started to become prescribed more.

In 1998, soft contact lenses started to be made out of silicone hydrogel, which has a high water content and is much more oxygen permeable.  That’s what soft contact lenses are still made out of today.

So I am grateful for my soft, comfortable contact lenses. Imagine just sticking a massive, expensive bit of glass in your eye that you have to take out insurance for!

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