What Is Silicone Hydrogel

 

Silicone hydrogel contact lenses are advanced soft lenses that allow more oxygen to pass through the lens to the cornea than regular soft ("hydrogel") contacts. In fact, silicone hydrogel lenses enable up to five times more oxygen to reach the cornea than regular hydrogel lenses.

Silicone hydrogel and regular hydrogel lenses both are made of plastics that are hard when dry but readily absorb water and become soft and gel-like when hydrated. If we have ever let a soft or silicone hydrogel lens dry out, we know that it becomes deformed, hard and fragile. But if we soak it for a few minutes in contact lens solution, it becomes soft and pliable again. Silicone hydrogel contact lenses sometimes are erroneously called silicon hydrogel lenses.

Silicon is a very common mineral. In fact, ordinary sand is composed primarily of silicon dioxide (silica). And highly purified silicon is used to manufacture semiconductors, which is why the southern part of the San Francisco Bay area, home of Apple and many other high-tech and computer companies, is nicknamed Silicon Valley.

Silicone hydrogel lenses are soft lenses, but silicone also is used in the production of many rigid gas permeable contacts for technology transfer to improve oxygen permeability of the lenses. All contact lenses reduce the amount of oxygen that reaches the front surface of the eye to some degree. When the cornea's oxygen supply is significantly reduced — a condition called hypoxia — a number of problems such as red eyes, corneal swelling, blurred vision and eye discomfort can occur. Hypoxia also can increase contact lens wearers' risk for a number of eye infections.

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