Silicone hydrogel contact lenses are soft contact lenses made from an advanced material with increased patient comfort and visual performance. Silicone hydrogel, also called Si-Hy, allows more oxygen to pass through the lens to the eye’s front surface, called the cornea. This means healthier eyes for wearers.
This increase in oxygen content allows for longer patient wear time, increased patient comfort, and better corneal health.
Silicone Hydrogel vs. Hydrogel – What Are The Differences
Prior to the existence of silicone hydrogel lenses, most soft contact lenses were made of regular hydrogel.
Hydrogel lenses were introduced in the late 1950s, and are naturally compatible with the human eye. They have a high water content which in theory sounds ideal, but sometimes this can actually worsen dry eye symptoms.
What are the benefits of silicone hydrogel contacts?
Silicone hydrogel lenses differ in their ability to allow oxygen to reach the cornea. Silicone hydrogel lenses allow up to 5 times more oxygen content to reach the front surface of the eye compared to regular hydrogel lenses. This can help prevent hypoxia from occurring, which is a very serious ocular condition that can cause redness, blurred vision, and eye infections.
Because these lenses allow more oxygen to reach the cornea, they can be worn for a longer period of time – aka extended wear. See the section below about sleeping in lenses for more information about extended wear.
Silicone hydrogel lenses are also slightly firmer than hydrogel lenses, making them easier to handle.
Is silicone hydrogel the best contact lens material?
The short answer is “yes.” However, the “best” contact lens material is different for every individual patient, so it is hard to label one material superior to others. In general, however, silicone hydrogel is superior to traditional hydrogel in terms of oxygen permissibility, which is superior for ocular health.
What are the different types of silicone hydrogel?
Each different lens manufacturer will use a different variation of a silicone hydrogel polymer in their lenses. For example, Acuvue Oasys lenses use Senofilcon A, whereas Air Optix Night & Day Aqua uses Lotrafilcon A.
The lens materials will even change within the same family of lenses at a manufacturer. For example, the Acuvue Vita lens has a greater oxygen transmissibility value and uses Senofilcon C vs. regular Acuvue Oasys lenses that use Senofilcon A.
Although the polymers vary, the mechanism of silicone hydrogel lens materials is very consistent throughout all brands.
Why are silicone hydrogel so popular?
Silicone hydrogel lenses are very popular due to the numerous patient benefits, as explained above. Research suggests that 77%* of all contact lens fits use silicone hydrogel, and that number is even higher in patients who use daily disposable lenses. Patients seem to like comfortable lenses that provide great vision, and silicone hydrogel lenses are able to do just that.
*Morgan P, Woods C, Tranoudis IG, et al. International Contact Lens Prescribing in 2019. Contact Lens Spectrum. 2020;35 (January 2020):26-32
Eyecare practitioners like prescribing silicone hydrogel lenses because they are arguably the safest lens material in terms of ocular health. The more oxygen that is delivered to the cornea, the better, which is why silicone hydrogel lenses are preferred over hydrogel lenses.
How to choose which silicone hydrogel contacts are best for me?
The best way to select the ideal silicone hydrogel lens for you would be to talk to your eye care professional. Your doctor will be able to assess the health of your eyes and make lens suggestions based on your daily visual needs.
Do they make specialty silicone hydrogel contacts?
Silicone hydrogel lenses are available in a monthly and a daily lens wear option. There are toric silicone hydrogel lenses available for patients with astigmatism and multifocal silicone hydrogel lenses available for patients with presbyopia.
Many contact lens manufacturers also allow specialty silicone hydrogel lenses to be ordered in extended parameters (for patients with very high or unique prescriptions).
Can you sleep in silicone hydrogel contacts?
The short answer is yes – there are some silicone hydrogel contact lenses that you are able to sleep overnight in! However, there are only a few brands that are FDA-approved to do so, and the length of overnight wear time differs depending on the brand.
A very popular brand that is approved for 30 nights of continuous wear is Air Optix Night & Day Aqua from Alcon. Acuvue Oasys lenses by Vistakon are also approved for up to 6 consecutive nights. However, many eye doctors still encourage removing these lenses nightly to avoid potential infection.
If you are interested in finding a brand of silicone hydrogel contact lenses that you are allowed to sleep overnight in, contact your eye doctor for their recommendation. The ability to sleep overnight in these lenses depends on each patient’s ocular health and ocular history, so it is important to have your eyes examined by an eye care professional prior to sleeping in these lenses.
Do Silicone Hydrogel contacts have the highest water content and oxygen transmissibility?
High water content and oxygen transmissibility do not actually go hand in hand. In fact, lenses that have higher oxygen transmissibility often have a lower water content due to the nature of the lens technology. The silicone material is naturally water repellent, so while it has high oxygen transmissibility, it has low water content.
If you suffer from dry eye or have a history of very sensitive eyes, it is important to consider what lens materials might be best for you. Dry eye is different for each patient, and each patient might find success in different lens materials.
Do silicone hydrogel lenses increase the risk of keratitis?
There is mixed literature when considering the risk of keratitis (inflammation and infection of the cornea) associated with silicone hydrogel use. Some studies suggest that these lenses increase the risk of keratitis, while others claim that they reduce the risk.
However, the literature is conclusive in finding that there is a significantly higher prevalence of keratitis in patients who sleep in their lenses overnight unadvised. As a contact lens wearer, the best thing that you can do to limit your chance of keratitis is to regularly change out your contact lens as directed, maintain a proper contact lens cleaning regimen, and not sleep overnight in your contact lenses (unless advised to do so by your eye doctor).
Can you be allergic to silicone hydrogel? How can you tell?
As with most other plastic materials that come into contact with the human body, it is possible to be allergic to silicone hydrogel (however, this is quite rare). Therefore, a person that is already aware of a silicone allergy may not be able to wear silicone hydrogel soft contact lenses.
A person experiencing an allergic reaction to silicone hydrogel lenses might experience redness, discomfort, itchiness, foreign body sensation, dryness, or greater awareness of the lens. If you are experiencing any of these symptoms while wearing a silicone hydrogel lens, contact your eye doctor immediately to rule out an allergic reaction.
It would be quite rare for this to be a true allergic reaction in response to a silicone hydrogel material. Instead, these symptoms are more likely related to contact lens dryness or sensitivity to a new contact lens solution.
What are some of the leading silicone hydrogel contact lenses?
There are many different brands and manufacturers of silicone hydrogel lenses. Some of the most popular brands include:
Dr. Olivia Burger, O.D. is an optometrist who graduated from the Pennsylvania College of Optometry. She is pursuing a 1-year residency at the UC Berkeley School of Optometry in Vision Science in Primary Care / Contact Lens. Her optometric areas of interest include private practice, contact lenses, and optometric service organizations such as VOSH. In her free time, she enjoys live music and is a freelance concert photographer.