Extended wear of contact lenses basically refers to the process of wearing contact lenses continuously including overnight during sleep for extended periods. An extended period would usually be defined as one or more consecutive night of contact lens wear. The benefit of extended wear compared to daily wear is primarily the convenience of not having to remove the contact lenses as frequently.
Both soft and rigid contact lenses can be used for extended wear. However, in this case, they must be made of a material that has high oxygen permeability so that the cornea is able to receive sufficient oxygen during overnight wear. Rigid contact lenses made from highly oxygen permeable materials have been available for many years. The new generation of soft extended wear contact lenses are made of a silicone-hydrogel material which provides these new lenses with an oxygen transmissibility up to five times that of the best previous soft extended wear lenses.
As contact lenses are worn in direct contact with the eye, contact lens wear involves certain risks. It is not possible to predict all of the possible complications which may occur with contact lens wear. However, certain conditions are more commonly associated with extended wear, including
Most of these conditions are reversible with early attention. However, permanent loss or reduction of vision is possible should one of the more serious side effects occur, such as microbial keratitis. This disease, if not treated promptly, has the potential to cause permanent scarring of the cornea with an associated reduction in best corrected visual acuity, and may even lead to blindness in extreme cases.
The use of contact lenses with high oxygen transmissibility will diminish some, but not all, of the risks normally associated with extended wear. It is important to understand that risks still exist and that the lens wearer must bear a significant responsibility for the ongoing health of their eyes during extended wear. Extended wear contact lens patients must be aware that they should remove their lenses immediately and contact their contact lens practitioner as soon as possible if either eye becomes red or painful, the lenses become uncomfortable, vision with the contact lenses becomes blurred or either eye becomes photophobic (very glare sensitive).
Contact lens-related infections are very rare and most contact lens wearers will never have one. It has been estimated that the incidence of microbial keratitis with daily wear of contact lenses is around 0.1% per eye per annum while studies have shown that wearing contact lenses during sleep further increases this risk some four-fold.
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