Tell Me About Silicone Hydrogel
Whoever invented Silicone Hydrogel was a hero - and a true friend of your eyes.
To understand why, here’s a short history lesson.
THE ORIGINS OF CONTACT LENSES
The idea of the contact lens was dreamed up by Leonardo da Vinci in the 16th century (he seems to have thought of everything). However, it took until the 1880s - when glass contacts were conceived - to turn the idea into a reality.
By the late 1940s, plastic contact lenses had arrived. There was a problem though: not being porous for oxygen, this vital form of nourishment couldn’t pass through. As a result, these rigid lenses couldn’t be worn for long.
The true ancestor of today’s contact lenses was invented in the late 1950s, using hydrophilic (‘water loving’) hydrogel soft contact lens material . The first contact lenses of this type were launched commercially in the early 1970s. Gas permeable rigid contact lenses soon followed, combining the smaller hard structures of the late 1940s with breathability.
Naturally, people loved these contact lenses for the freedoms they introduced, but often forgot to clean, disinfect and store them properly, or take them out at night. Overuse and other unhealthy practices led to red, tired or (at worse) damaged eyes.
Today, science has taken contact lens wear to a new level of comfort. As a result, the rise and rise of the modern soft contact lens in recent decades has revolutionised people’s lives.
The key has been the development of water-loving hydrogel contact lenses, since the 1970s . These combine moulded plastic and water, to create a precise hydrogel contact lens, highly compatible with the human eye. Even for people with sensitive or dry eyes, they’re a great contact lens choice - soft and comfortable.
However, nothing in life is perfect. A hydrogel lens’ water content can reduce if you don’t blink enough, or find yourself in a dry, windy environment. The lens surface may also dry out after a whole day’s use. In such cases, hydrogel contact lenses can become less comfortable to wear. But thankfully there’s a more recent soft lens. Interested? Then read on ...
The more advanced 21st century alternatives (invented in 1998) are contact lenses made from silicone hydrogel. These work in exactly the same way as their hydrogel cousins, but add the benefits of silicone, increasing oxygen permeability. This allows more air - and hence oxygen - to pass through the contact lens.
In fact, these clever inventions allow more oxygen to reach the cornea than a standard hydrogel soft lens, keeping your eyes healthy and comfortable even when you wear contacts for a whole day. And because these silicone hydrogel contact lenses retain water, they stay particularly soft and flexible throughout the entire period.
WHY DOES THE EYE NEED OXYGENATING?
This oxygenation is important. If the flow of air and the film of tears around your eyes is restricted, it can result in signs and symptoms of hypoxia, caused by insufficient oxygen supply. The cornea itself contains no blood vessels (they would impair optical transparency), so its most important oxygen supply comes directly from the atmosphere, via the tear film covering your eye.
A reduction in oxygen supply and consequent hypoxia might give you blurry vision - caused by a swollen cornea - or worse, if oxygen is absent or restricted for a long period. It can also lead to red eyes, as engorged blood vessels try to deliver oxygen to your cornea. Blood vessels may start growing towards your pupils, attempting to replenish oxygen-deprived areas: this is not reversible. Your eyes could become more easily infected or otherwise permanently damaged.
Wearing a silicone hydrogel lens is a great way to enjoy contact lenses without risking such unpleasant issues. You can continue wearing them for longer hours than hydrogel contact lenses, whilst preserving good eye health. This makes them particularly popular with people who enjoy active lives, have dry eyes, or who spend their days in front of screens.
A SILICONE HYDROGEL LENS FOR EVERY PERSON, NEED OR OCCASION
Silicone hydrogel materials are used to make all types of contact lens, from super-soft daily disposables to more robust monthlies. Silicone - which enables flexibility - is also used in modern gas permeable contact lenses. It has also enabled extended wear lenses, worn for weeks or even a month at a time.
Are there any problems associated with this smart material?
Well, silicone hydrogel contact lenses are slightly more expensive than hydrogel equivalents. They also tend to collect more lipid (fat) deposits than other contact lenses, making monthlies harder to keep clean.
If you are prone to dry eyes, silicone hydrogel technology lenses will outperform their hydrogel counterparts. As with any physical barrier, there will still be a limit on the amount of time you can wear lenses comfortably. However, before recommitting to glasses, you may find that using silicone hydrogel monthlies with a specially formulated contact lens cleaning solution could solve the problem, helping your eyes stay fully hydrated and comfortable.
YOUR ENHANCED FUTURE – VISUAL FREEDOM
Silicone hydrogel has taken contact lenses into a new era of comfort and safety, creating tiny miracles of vision enhancement.
For almost any visual correction or cosmetic need, choosing to wear silicone hydrogel lenses can turn each day into a clearly focused delight.
References: 1. Stacy, S. (2010). "Some Facts About SiHy Lenses." https://www.reviewofoptometry.com/article/some-facts-about-sihy-lenses. Accessed: 10/03/2021 2. Your eyes and oxygen. https://www.oxygenworldwide.com/news/articles-and-information/635-your-eyes-and-oxygen. Accessed: 10/03/2021