Silicone Hydrogel Contact Lenses
A comprehensive look into how silicone hydrogel contact lenses are made, worn, and cared for.
Silicone Hydrogel contact lenses are literally a breath of fresh air for eye care patients. Brought onto the market in 1999, they are made of high oxygen-permeable plastic that allows up to seven times more oxygen to flow into the cornea than conventional contacts, and they are described as 100 percent more comfortable. Half of all contacts today are made of silicone hydrogel, and many eye care practitioners believe that within the next few years, more patients will be wearing silicone hydrogel lenses than any other lens material.
Types of Silicone Hydrogel Contact Lenses
There are three types of silicone hydrogel lenses available. They are spherical, toric, and bifocal. The difference among these contact lenses is how long they are meant to be worn. Patients can choose from daily disposals, six-day extended wear, two-week daily wear, or thirty-day continuous and daily wear lenses. To determine which lens would benefit you, talk to your doctor about your options, taking into account the sensitivity of your eyes.
The brands of spherical silicone hydrogel lenses currently available, in order of highest oxygen transmissibility to lowest, are:
- Ciba Focus Night & Day; approved for up to thirty day continuous wear.
- Coopervision Biofinity.
- Purvision by Bausch and Lomb; approved for up to thirty days of continued wear.
- Ciba 02 Optic and Airoptix Aqua; approved for two week daily wear or up to six nights of extended wear.
- Acuvue Oasys; approved for two week daily wear use or six night extended wear and designed to be wetter than the others.
- Coopervision Avaira; at this time approved only for daily wear and two week replacement.
- Acuvue Advance; approved for two weeks daily wear.
There are also currently several toric (astigmatism correcting) silicone hydrogel lenses on the market:
- Bausch & Lomb PureVision Toric: approved for thirty days extended wear use
- Acuvue Advance for Astigmatism: approved as a two week daily wear lens.
- Ciba Airoptix for astigmatism: approved for two to four week replacement and up to six nights of extended wear.
- Acuvue Oasys for astigmatism: approved for two weeks of daily wear or up to six nights of extended wear.
- There is one silicone hydrogel multifocal, the Purevision Multifocal: approved for daily wear or up to thirty 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, but 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-based lens materials usually have low surface energy, and as a result have decreased surface wetting.
Benefits vs. Conventional Contacts
The biggest difference patients can perceive is that they are more comfortable than conventional contacts. Also, silicone hydrogel contacts help minimize problems like redness, dryness, swelling of the cornea, and corneal infections. And any infections that do appear tend to be less aggressive and more treatable. Silicone hydrogel lenses allow more oxygen to reach the cornea, which improves 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 the greater rigidity of the material, and 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 and discomfort. Other patients are just not able to adapt well to the more rigid silicone material. So what is beneficial to one patient can have a negative effect on another. It is very important to consult 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 rather than conventional soft lenses due to the health advantages, but these lenses are especially useful for the following types of patients:
- Patients with high prescriptions
- Patients whose eyes 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 twelve to fourteen hours a day, including overnight wear
- Younger patients who tend to over-wear their lenses or do not clean them properly or as often as recommended
Daily Care Instructions
There is a 1 in 2,500 chance of developing an infection if the patient chooses to wear their contacts for a long time. Patients are encouraged to take their lenses out nightly to reduce these chances. Washing your hands before putting in or taking out lenses is also important. Follow these simple guidelines for the daily care of your lenses:
- Rub your lenses when you clean them; soaking alone does not remove debris.
- Clean your lens case daily with hot water. Let it 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 is 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 are expensive. There are different places to buy Silicone Hydrogel Lenses: you can get them from your eye care practitioner, optical chains like LensCrafters, warehouses like Costco, or any of various online retailers.
Before you purchase Silicone Hydrogel Lenses, there are a few things you have to take into consideration such as 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. Doctors use silicone medically for many different purposes, and they say patients usually only encounter problems when they switch 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 about switching to silicone hydrogel lenses, bring the matter up with your doctor.
Talking to Your Eye Doctor
Here are some questions to ask your eye care provider about silicone hydrogel contact lenses:
- Are silicone hydrogel contact lenses suitable for me?
- Do you have any concerns about this type of contact lens?
- Have you ever come across anyone who was allergic to the material?
- How much should I expect to pay for these lenses?
- Am I a good candidate for these lenses, or is there a better alternative?
- Which silicone hydrogel lens do you recommend for me?
Safety Updates: What’s New?
In May 2007, the FDA issued an alert about Complete MoisturePlus Multi-Purpose Solution. This contact lens product, which is 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 they have now come out with a re-branded solution called Complete Easy Rub.
In 2006, the FDA issued an alert about Bausch & Lomb’s ReNu with MoistureLoc, claiming it was linked to a fungal infection. In this case, the solution had inadvertently created an environment in which fungi thrived. Even though researchers found that lens wearers who had been careless about cleaning and replacing solution every day were the only ones who got infections, these products were still taken off the market.
In June of 2010, Johnson & Johnson Vision Care introduced their new product, 1-Day Acuvue TruEye. This new lens is made of silicone hydrogel and has been approved by the FDA as the first ever daily disposable contact lens made of this material in the US.