With more than 150 million people across the globe wearing contact lenses, we immediately know two things: you’re either one of them, or you know someone who plopped two slippery shells of clarity onto their corneas today.
And here’s one eye-opening fact everyone should know about these discreet vision enhancers: they would not be possible without the oil industry. Yes, there’s oil in those lenses. Let us explain.
An uncomfortable history
The earliest contact lenses were invented in the 1880s using glass. That's right—glass in your eye. They were invented independently by three men: Dr. Adolf Fick, Eugene Cult and Louis J. Girard. Dr. Fick proposed the contact lens in his treatise titled, "A Contact Spectacle."
These lenses were made using blown glass, making them heavy and uncomfortable. Worse, they covered the entire eye and didn't allow oxygen to pass through, effectively suffocating the eye. Wearers would complain of excruciating eye pain after a few hours of use.
Things improved in the 1930s when new plastics made it possible to produce lightweight contact lenses. It got better in 1948 with the invention of the corneal contact lens (i.e., the lens covered only the cornea, not the entire eye). And things really got going in 1953 when Czechoslovakian chemist Otto Wichterle invented a new type of plastic called hydrogel. It could be shaped and molded like other plastics. But it also could absorb up to 40 percent water and became soft and pliable when wet: the perfect material for a comfortable-to-wear contact lens. In the 1960s, Bausch and Lomb got access to hydrogel and developed a process to mass produce 'soft' contact lenses.
Since then, both hard and soft contact lenses have continued to improve, particularly in terms of oxygen permeability to allow the eyes to breathe.
The chemistry of contacts
There are two types of contact lenses – soft, and rigid gas-permeable (RGP), commonly called hard lenses. Soft lenses are the most popular, with about 80 per cent of the market.
For both types, polymers are a key ingredient. In fact, polymers make up nearly 100 per cent of soft contact lenses. A polymer is a chain-like molecule made by combining many small molecules called monomers. Some polymers are natural – think proteins, cellulose and starch. Other polymers are human-made, produced by complex chemical reactions termed polymerizations. And they’re everywhere. From bike tires to television remotes to fibres for clothing to contact lenses, polymers are right under our nose. Or, in this case, right above it.
Typically, less than five per cent of a petroleum barrel is used for polymers making polymers both a low-cost and abundant resource. And while the process used to make contact lenses changes crude oil to something much more refined, oil is the basic source and indispensable to the contact-making process.
How are contact lenses made?
There are three methods:
- Spin casting – liquid silicone is spun on a revolving mold, where it polymerizes.
- Molding – liquid polymer is injected onto a rotating mold. Centripetal force (a force that makes something follow a curved path) shapes the lens as the plastic polymerizes. Molded contacts are moist from start to finish. Most soft contacts are made using this method.
- Diamond turning (lathe cutting) – an industrial diamond cuts a disk of polymer to shape the lens, which is polished using an abrasive. Both soft and hard lenses can be shaped using this method. Soft lenses are hydrated after the cutting and polishing process.