What are Eye Contacts Made Of?

Early Eye Contacts

Eye contact lenses were first developed in the 1960s, and have continually improved. The early contact lenses were known as hard contact lenses. That is, these lenses were rigid. They were made of a plastic called polymethyl methacrylate (PMMA). This was a durable plastic but did not allow oxygen to pass through it. Later developments allowed for hard contact lenses to be permeable to oxygen; that is, they allowed oxygen in the air to reach the cornea. This is important because the central anterior cornea depends on the atmosphere for oxygen. Without enough oxygen, the eye can develop corneal edema.

Hard Contact Lenses

There are two main categories of modern contact lenses. These categories are hard and soft lenses. Because modern hard contact lenses are gas permeable, and also because it is the main feature of these lenses, they are known as rigid gas permeable lenses (RGPs). These lenses are made of plastics that are combined with other materials like silicone and fluoropolymers. Bifocal lenses and toric lenses (lenses made for people with astigmatism) can be either RGPs or soft contact lenses.

Soft Contact Lenses

Soft contact lenses are made from a soft plastic material that is combined with water. The water allows the eye contact lens to be easily bent with slight finger pressure, a feature that makes them more comfortable to wear, but it also makes them easier to tear. Soft contact lenses also allow oxygen to reach the cornea. More than three-fourths of contact wearers in the United States wear soft contact lenses. There are two basic types of soft contact lenses: disposable (daily wear) and extended wear. Extended wear lenses are made with a silicone hydrogel, and they can be worn continuously for up to 30 days and nights. The silicone allows for greater oxygen transmission to the cornea. Because extended wear lenses are worn for greater periods of time than daily wear lenses, the added permeability for oxygen is an important feature. Extended wear lenses also have a higher water content than daily wear. This is one reason why oxygen passes more easily through them. The high water content also allows for the contact lenses to float more freely on the eye, making them more comfortable. Even with the increase in oxygen permeability, the corneas for some people still might not get enough oxygen with them, and so they can switch to daily wear lenses, which are taken out each day, allowing for corneas to get more oxygen.