Silicone Hydrogel Contact Lenses
A comprehensive look into how silicone hydrogel contact lenses are made, worn, and cared for.
Silicone Hydrogel contact lenses are a breath of fresh air for the eyes for patients, literally. Brought into the market in 1999, they are made of a high oxygen permeable plastic that allows up to 7 times more oxygen to flow into the cornea compared to conventional contacts, and are described as 100% more comfortable. Half of the contacts today are made silicone hydrogel and many eye care practitioners believe that within the next few years, more patients will be wearing silicone hydrogel lenses over any other lens material.
Types of Silicone Hydrogel Contact Lenses
There are 3 types of silicone hydrogel lenses available. They are spherical, toric and bifocal. The difference between these contact lenses is the wear length. Patients can choose between daily disposals, 6-day extended wear, 2-week daily wear, or 30-day continuous and daily wear lenses. To determine which lens would benefit you, talk to your doctor about the options you have, along with the sensitivity levels your eyes can handle
The current brands of spherical silicone hydrogel lenses available, in order of highest oxygen transmissibility to lowest, are:
- Ciba Focus Night & Day which is approved for up to 30 day continuous wear.
- Coopervision Biofinity.
- Purvision by BUasch and Lomb – approved for up to 30 days of continued wear.
- Ciba 02 Optic and Airoptix Aqua – approved for 2 week daily wear or up to 6 nights of extended wear.
- Acuvue Oasys – approved for 2 week daily wear use or 6 night extended wear and is designed to be wetter than the others.
- Coopervision Avaira – at this time approved only for daily wear and two week replacement.
- Acuvue Adance – approved for 2 weeks daily wear.
There are also currently FOUR toric (astigmatism correcting) silicone hydrogel lenses on the market:
- Bausch & Lomb PureVision Toric is a silicone hydrogel toric lens approved for 30 days extended wear use
- Acuvue Advance for Astigmatism which is currently approved as a 2 week daily wear lens.
- Ciba Airoptix for astigmatism – approved for 2-4 week replacement and up to 6 nights of extended wear.
- Acuvue Oasys for astigmatism – approved for 2 weeks of daily wear or up to 6 nights of extended wear.
- There is one silicone hydrogel multifocal, the Purevision Multifocal, approved for daily wear or up to 30 days of continuous wear.
What’s In Silicone Hydrogel Contacts?
There are different materials in different brands of silicone hydrogel contact lenses. All of them contain silicone hydrogel and oxygen, however some of them include unique materials like Balafilcon A, in PureVision, Galyfilcon A in Acuvue Advance, Lotrafilcon A, in Night & Day, Lotrafilcon B in O2-OPTIX, and Senofilcon A, in Acuvue Oasys. Silicone-containing lens materials usually have low surface energy and as a result, have decreased surface wetting.
Benefits vs. Conventional Contacts
The biggest difference patients can tell is the comfort level versus conventional contacts. Also, silicone hydrogel contacts help minimize problems like redness, dryness, swelling of the cornea and corneal infections. Plus, any infections that do come about tend to be less aggressive and more treatable. Silicone hydrogel lenses allow more oxygen to the cornea which results in better eye health.
Other advantages of silicone hydrogel lenses over conventional lenses include more resistance to protein deposits, less drying of the lenses, lower risk of eye infection, easier handling due to increased rigidity of material, along with the high Dk levels which remove the risk of conditions like Hypoxia to the cornea.
Disadvantages vs. Conventional Contacts
Silicone hydrogel lenses may not be the choice for all patients. These lenses are generally more expensive than non-silicone lenses, so a more price conscious consumer may not prefer this option. Also, in some patients the silicone material tends to attract more lipid deposits, which may cause blurry vision along with discomfort. Other patients just are not able to adapt well to the more rigid silicone material, which may result in some minor defects to the cornea’s ability to function. So, what can be great and beneficial to one patient, can in fact have a negative effect for others. It’s very important to consult with your eye care practitioner before choosing to use silicone hydrogel lenses.
Who Can Wear Silicone Hydrogel Contacts?
Most people benefit from wearing silicone hydrogel lenses as compared to conventional soft lenses. This is due to the health advantages however, these lenses are especially useful in the following types of patients:
- Patients with high prescriptions
- Patients whose eyes show signs that they require more oxygen
- Patients who experience end of day discomfort, dryness, or redness with their conventional soft lenses
- Patients who work long hours in low humidity air conditioning
- Patients who wear their lenses for more than 12 to 14 hours a day, including overnight wear
- Younger patients who tend to ‘over-wear’ their lenses
Daily Care Instructions
There’s a 1 in 2,500 chance of patients developing an infection if they choose to wear their contacts for a long continuous amount of time. Patients are encouraged to take out their lenses nightly to lessen these chances. Washing your hands before putting in or taking out lenses is also important. Follow these simple guidelines to help with the daily care of your lenses:
- Rub your lenses when you clean them; soaking alone doesn’t remove debris.
- Clean your lens case daily with hot water. Let them air-dry, rinse with multipurpose solution, and fill the case with a fresh supply. Never top off old solution with new.
- Replace your case monthly.
- Keep your eyes moist. Use rewetting drops or artificial tears several times a day.
Buying Silicone Hydrogel Lenses
Before you purchase this type of lens, it’s important to know you will be spending more money regardless of where you buy them. They are new to the market, and like any new product, they’re more expensive. There are different places to buy from like your eye care practitioner, optical chains like LensCrafters, mass warehouses like Costco and online retailers.
But before you do there are a few things you have to take into consideration like your vision insurance, availability of the product, the bundled deals and rebates. Different places have different deals at different times. It really depends on you and how quickly you need your lenses. Besides the price of the lenses, you have to consider shipping costs as well as the value of your time.
Silicone Hydrogel Allergies
Evidence of silicone allergies during contact lens wear is pretty much non-existent. Practitioners have used silicone medically for many different reasons and say usually patients encounter problems with these lenses due to switching lenses. Other eye care practitioners say there are too many other possible culprits like bacteria, tear film proteins, dust, pollen and chemicals to put the blame solely on the silicone. If you have severe allergies and are concerned either before or after you switch to silicone hydrogel lenses, bring it up to your doctor.
In May 2007, the FDA issued an alert about Complete MoisturePlus Multi-Purpose Solution. The contact lens product, made by Advanced Medical Optics, had been linked to an unusual number of serious eye infections like Acanthamoeba keratitis (which is caused by a parasite). Since then, Advanced Medical Optics has made changes to comply with FDA standards and came out with a re-branded solution called Complete Easy Rub. In 2006, the FDA issued an alert about Bausch & Lomb’s ReNu with MoistureLoc, was linked to a fungal infection. In this case, the solution had created an environment in which fungi thrived without realizing it. Even though researchers found that lens wearers who’d been careless about cleaning and replacing solution every day, were the ones who got infections, these products were still taken off the market.