Silicone hydrogel lenses are contact lenses made from a material that combines silicone with a water-absorbing polymer, allowing significantly more oxygen to pass through to your cornea than traditional soft lenses. They’ve dominated the contact lens market since their introduction in 1999 and are now the most commonly prescribed type of soft contact lens worldwide.
How They Differ From Traditional Soft Lenses
Traditional soft contact lenses, known as conventional hydrogels, rely on water content to transport oxygen to the cornea. The more water in the lens, the more oxygen gets through. This works reasonably well while your eyes are open, but it creates a ceiling: you can only pack so much water into a lens before it becomes too fragile or unstable to wear.
Silicone hydrogel lenses solve this by using silicone-based components that are inherently permeable to oxygen, independent of water. Silicone dissolves oxygen far more readily than water does, so the material itself acts as an oxygen highway. The hydrogel portion of the lens still provides the flexibility and moisture that make it comfortable on the eye, but the silicone does the heavy lifting when it comes to oxygen delivery.
The difference is dramatic. Oxygen transmissibility is measured in units called Dk/t. Traditional hydrogels generally reach about 24 Dk/t, which is enough to prevent corneal swelling while your eyes are open during the day. Silicone hydrogels typically exceed 87 Dk/t, which is the threshold needed to keep the cornea healthy even during sleep, when your eyelids are closed and cutting off the cornea’s main oxygen supply from the air.
Why Oxygen Matters for Your Cornea
Your cornea is one of the few tissues in the body that has no blood vessels. It gets its oxygen directly from the air (or, when your eyes are closed, from the blood vessels lining the inside of your eyelids). A contact lens sits right on top of this tissue, creating a barrier. If the lens doesn’t let enough oxygen through, the cornea swells, new blood vessels can grow into it from the surrounding tissue, and over time this can affect vision clarity and eye health.
With traditional hydrogels, wearing lenses overnight was risky because the combination of a closed eyelid and a low-oxygen lens essentially suffocated the cornea. Silicone hydrogels were specifically developed to address this. Some silicone hydrogel lenses are approved for extended or overnight wear for this reason, though sleeping in any contact lens still carries a higher infection risk than removing them each night.
Common Brands and Types
The first silicone hydrogel lens to hit the market was PureVision by Bausch & Lomb in 1999. CIBA Vision’s Night & Day (now sold as Air Optix Night & Day) followed shortly after. Since then, the category has expanded rapidly. Acuvue Oasys, Biofinity, Air Optix, and Dailies Total1 are among the most widely prescribed silicone hydrogel brands today. They’re available in daily disposable, two-week, and monthly replacement schedules, as well as in prescriptions for astigmatism and multifocal needs.
Comfort and Stiffness
Early silicone hydrogel lenses had a notable drawback: they were stiffer than traditional hydrogels. The silicone component increases the material’s rigidity, which some wearers could feel on the eye. This stiffness, referred to in the industry as modulus, contributed to issues like small pressure marks on the cornea and irritation of the tissue under the upper eyelid.
Newer generations of silicone hydrogels have been engineered with lower modulus values, making them softer and closer in feel to traditional hydrogels. Comfort with any contact lens depends on multiple factors beyond just oxygen permeability: how well the lens surface stays wet between blinks, how much the lens dehydrates over a wearing day, how the edge of the lens is shaped, and how resistant the surface is to buildup from your tears.
Deposits Build Up Differently
Every contact lens accumulates deposits from your tear film over time, but the type of deposit varies by material. Traditional hydrogels tend to attract more protein deposits. Silicone hydrogels attract less protein overall but are more prone to lipid (oil-based) deposits. This is because the silicone component has a natural affinity for nonpolar, oily substances.
Lipid deposits can make lenses feel greasy or hazy and may contribute to discomfort toward the end of the day. If you wear reusable silicone hydrogel lenses (two-week or monthly), cleaning them thoroughly each night with a rubbing step is more effective at removing lipid buildup than a soak-only routine. Daily disposable silicone hydrogels sidestep this issue entirely since you discard them after a single use.
Silicone Hydrogels and Dry Eyes
The relationship between silicone hydrogel lenses and dry eyes is more nuanced than many people expect. Because these lenses don’t rely on water content for oxygen delivery, they can be made with lower water content, which means they pull less moisture from your tear film. In theory, this should help with dryness.
In practice, any contact lens disrupts the natural tear film. When a lens sits on the eye, it splits the tear layer into a thin film above the lens and another below it. The layer above the lens has a thinner lipid (oil) coating, reduced tear volume, and a faster evaporation rate compared to a normal, undisturbed tear film. These changes can worsen dry eye symptoms regardless of the lens material. For people with existing dry eye or oil gland problems in their eyelids, silicone hydrogels may not automatically be more comfortable than other options.
That said, many people with mild dryness do find silicone hydrogels more comfortable than traditional hydrogels, particularly toward the end of a long wearing day. The lower dehydration rate of the lens itself means it’s less likely to “steal” moisture from your eye as the hours pass.
Who Should Wear Them
Silicone hydrogel lenses are suitable for most contact lens wearers and are the default recommendation for new fits in most practices. They’re particularly beneficial if you wear lenses for long hours, work in dry or air-conditioned environments, or have been told your corneas show signs of oxygen deprivation from previous lens wear.
Some people, however, do better with traditional hydrogels. If you have sensitive eyes that react to the slightly stiffer feel of silicone hydrogel material, or if you experience persistent lipid deposits that cloud your vision, a high-water-content conventional hydrogel worn on a daily disposable schedule may be more comfortable. The “best” lens material is the one that balances oxygen delivery, comfort, and visual clarity for your specific eyes and lifestyle.