How do contact lenses work?

Medically reviewed by Sharon Copeland 17/02/2021

Why are contact lenses called ‘contact lenses’?

Named ‘contact lenses’ because they’re literally lenses that come into contact with the eyes, they ensure clear vision for the wearer by focusing light and correcting refractive errors. What makes lenses most different from glasses is that they float on the tear film and move with your eyes.

Since the development of soft contact lenses in 1971, many different types of contacts have been created. Made from different materials, with different qualities and designed for a different period of wear, the contact lens range available today can cater for anyone and everyone’s needs. Contact lenses seem to be a recent phenomenon, the famous inventor Leonardo da Vinci (1452-1519) produced the first known sketches (in 1508) that suggested the optics of the human eye could be altered by placing the cornea directly in contact with water. He demonstrated how seeing through the bottom of a glass bowl filled with water could help rectify the issue. While dunking your face in a bowl of water is a clearly impractical way of doing things, his method does acknowledge the necessity of the lens making contact with your eye!

Read our guides on how toric lenses for astigmatism and multifocal contacts work in specific ways to correct eye conditions.

What are contact lenses made of?

Soft contact lenses are made from light and flexible plastic, as opposed to hard (or rigid gas permeable) contacts that are formed out of a firmer and more durable plastic. This allows them to be more breathable than their hard counterparts, keeping eyes fresher for longer.

Most contact lenses are composed of a standard hydrogel makeup. This is comfortable and affordable. Other and generally higher quality contact lenses are also made from silicone hydrogel material, an advanced plastic material. Silicone hydrogel contact lenses work to absorb and lock in water during wear. This keeps the lens soft and comfortable, also keeping your eyes well-hydrated and fresh. One of the major benefits of silicone hydrogel lenses is their extremely high level of breathability – up to six times the amount of oxygen is allowed to flow through the lens to your eye when compared to other soft contact lenses.

When it comes to contacts, does one size fit all?

There is no ‘one size fits all’ contact lens. Unfortunately, contact lenses do not all come in one size, with each lens having a specific base curve and diameter. This is because people have different sized eyeballs, and some even have astigmatism – which means their eyeball is less round and more like a rugby ball in shape. In these cases, it’s not just base curve and diameter that affect the size and shape of a contact lens, the axis of a lens is also important if you’re wearing toric contacts to correct astigmatism.

The size and shape of the contact lens needed to fit your eye, as well as your prescription, will be prescribed and written down for you when you go for a contact lens fitting or aftercare. After you have been properly fitted, you may purchase the exact same contact lenses online for cheaper.