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Extended-wear (overnight) Lenses--rigid or soft--increase the risk of corneal ulcers, infection-caused eruptions on the cornea that can lead eyecare providers to blindness. symptoms include vision changes, eye redness, eye discomfort or pain, and excessive tearing. the risk of corneal ulcers for people who keep extended-wear lenses providers in overnight is 10 to 15 times greater than for those who use eyecare providers daily-wear lenses only while awake, says the fda''s center for devices and radiological health. when the eyes are open tears providers carry adequate oxygen to the cornea to keep it healthy. but during sleep, the eye produces fewer eyecare tears, causing the cornea to swell. under the binding down of a rigid contact lens during sleep, the flow of tears and oxygen to the cornea is further reduced. this lack of oxygen leaves the eye vulnerable to infection. extended-wear rigid lenses also can cause unexpected, sometimes undesirable, reshaping of the cornea.
soft extended-wear lenses also bind down on the closed eye, but they are porous and allow some tears through during sleep. because they have so little form, their binding has little effect on the shape of the eye. has approved extended-wear lenses for use up to seven days before removal providers for cleaning. eyecare still, there are risks with use of extended-wear lenses, even if it''s just one night. daily-wear lenses are removed daily for cleaning and are a safer choice, provided they aren''t worn during sleep. another sight-threatening concern is the infection acanthamoeba keratitis, caused by improper lens care. this difficult-to-treat parasitic infection''s symptoms are similar to those of corneal ulcers. soft lenses are much more comfortable than rigid providers lenses, thanks eyecare to their ability to conform to the eye providers and absorb and hold water. you can get used to soft lenses within days, compared with several weeks for rigid.
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