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Corneal Swelling (Edema)
Corneal edema, or swelling, occurs when there is an
inadequate supply of oxygen reaching the cornea due to
contact lens wear. Essentially, the cornea becomes
smothered by the lens. Sleeping in contact lenses, as with
extended wear lenses, greatly increases the risk of
corneal edema. In this situation, even less oxygen reaches
the cornea because the eyelid is closed over it. Also, the
normal blinking of the eye is not present, which helps
tears and oxygen to circulate under the lens.
Symptoms of corneal edema included blurred or foggy vision,
seeing rainbows around lights, redness, and possibly
irritation or pain. Complications of corneal edema include
corneal abrasion, a tight lens syndrome (see above), and
corneal ulcer or infection. Generally, a lens should not
be worn if symptoms of corneal edema are occurring.
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