Contact lenses have come a long way since the day when they were made of non permeable materials like glass or hard plastics. One company has been a leading innovator in this industry. The Acuvue Oasys 2 contacts are one of their latest and greatest new products.
The first contacts developed did not allow any oxygen at all to pass through. The cornea is a tissue lacking any blood vessels. It receives nutrients by way of diffusion from tear fluid outside the eye and the aqueous humor inside as well as through neurotrophins delivered through nerve fibers.
The only means of getting oxygen to the cornea is through contact with air in the atmosphere. Wearing lenses, that do not allow this air to pass through, directly on the eye, limits the available oxygen considerably. Oxygen is then only supplied to through tears, which are delivered beneath the lens by continual blinking. Once insufficient blinking to circulate the tears occurs, the cornea begins to be oxygen starved, painful, and eventually experience tissue death.
During the 1960s soft plastics called hydrogels were developed. These allow oxygen to pass through the lens due in part to their high water content, adding greatly to the comfort level and safety of lenses. As a trade off, the high water content necessitated that the lens be thicker for durability. Later improvements occurred with the introduction of silicone hydrogel. This material allows 98% of available oxygen to pass through. It is also more durable, allowing for thinner lenses.
Another factor that can affect permeability is organic build up on the lens surface. This can be lessened by meticulous cleaning. This problem was addressed by Acuvue’s introduction of disposables. Changing to fresh lenses daily, or biweekly with extended wear, does not allow the build up to affect permeability.
Besides breathability, other comfort factors are wetability and smoothness. Wetting agents were applied to the lenses, in storage, to keep them moist and smooth during use. The problem was that the longer they are worn, the less wetting agent remained. Acuvue’s Hydraclear Plus technology solved this problem. The wetting agent is now permanently embedded, enabling the lens to maintain both wetness and smoothness.
Extended wear is another innovation. This allows the lenses to be worn for two weeks before disposed of, if removed and cleaned daily. Alternatively they may be worn continuously for up to 6 nights, before replacing with a fresh pair. Many users desire the convenience of being free from wearing glasses at all, or of awakening from sleep and being able to see clearly immediately.
The new lenses also offer UV protection. They absorb up to 96% of UVA and UVB. High levels of UV rays can cause sunburn of the cornea. Some experts also believe blocking these rays will help prevent cataracts from forming in the cornea.
The Acuvue Oasys 2 contacts are one of the latest examples of technology improvements in lenses. This latest development makes lenses so comfortable that the wearer almost can not tell he is wearing them.
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