Silicone hydrogel contact lenses

Silicone hydrogel contact lenses are named for the materials used to make these lenses. As with many things, contact lenses have progressed as people develop better technology and materials. But how exactly do different silicone hydrogels make contact lenses better? We walk through what they are and how they make a difference.

What are silicone hydrogel contact lenses?

Soft contact lenses were made possible in the 1960s and 1970s by the development of water-loving polymers: large molecules made of repeated pieces (think of a long train of many railcars). These were called "hydrophilic gels" or simply "hydrogels." 

Silicone hydrogels are the latest in a line of developments in soft lens material aimed at increasing the oxygen permeability (increased comfort, longer wear and better eye health), wettability (better comfort) and clinical performance of contact lenses. Silicone has higher oxygen permeability, allowing more oxygen to pass, than water, so oxygen permeability is no longer tied to how much water is in each lens.

Silicone is the name used to describe plastic materials with a gel-like consistency that contain silicone, as well as oxygen, carbon and other elements. It’s an extremely flexible material, which makes it excellent for making not only contact lenses, but many other medical products such as implants and tubing.1

Types of silicone hydrogels.

There are many types, even generations, of silicone hydrogels used to manufacture contact lenses today. These come with technical names such as galyfilcon, senofilcon, comfilcon and enfilcon.

Each contact lens, whatever the material, is U.S. FDA-approved or cleared for specific wear and replacement conditions. While silicone hydrogels generally improve comfort and allow longer wear, check with your doctor about which contact lenses are right for you.

Benefits of silicone hydrogel lenses.

If the amount of oxygen reaching the cornea is significantly low - a state referred to as hypoxia - many uncomfortable conditions can occur in the wearer. These include red eyes, swollen corneas and blurred vision; hypoxia can also increase the risk of developing an eye infection.2  With greater oxygen allowance to the cornea, silicone hydrogel lenses can help minimize this risk.

Silicone hydrogel lenses reduce the tradeoff between oxygen permeability and wettability.

This opens up many possibilities for silicone hydrogel contacts, including:

  • Extended wear (sometimes for up to six straight nights and days )
  • Continuous wear (sometimes for up to thirty days before replacement )
  • Increased comfort and performance

Choosing silicone hydrogels.

There are many different types of silicone hydrogel materials that are each used to make contact lenses that address different corrective and wearing needs. So, while knowing the benefits of silicone hydrogels can help inform your preferences, you should choose right contact lenses for you by consulting your eye doctor, and evaluating the wear and replacement schedules each contact lens is approved or cleared by the U.S. FDA.

Remember that while it might be cheap to buy  contact lenses online, some online lenses may not be approved or cleared by the U.S. FDA. All contact lenses should be prescribed for you by your eye doctor, and fitted for your eyes.

Nothing in this article is to be construed as medical advice, nor is it intended to replace the recommendations of a medical professional. For specific questions, please see your eye care practitioner.

References
1. Hydrogel vs silicone hydrogel contact lenses: a guide on the benefits and disadvantages. FeelGood contacts. April 2018.

2. What are silicone hydrogel contact lenses. VisionDirect.ie. Online. Accessed March 2019.
3. Image: L Jones & C Woods: An eye on the world’s first silicone hydrogel daily disposable contact lens. Optician 2008; 236;6172: 33 - 34

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