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Ask any daily wear contact lens wearer, and they will admit that they have left their lenses in overnight at least once. This is despite being advised by their optician that this is not safe for daily wear lenses.
More often than not, you might leave your lenses in by accident. But sometimes the hassle of removing, or even cleaning contact lenses can seem like one task too many at the end of a busy day.
Often this will result in nothing more than gritty, sore eyes – making you think that the risks of leaving your lenses in place have been over-exaggerated by your optician.
However, a significant risk associated with overnight wear is infection; most commonly microbial keratitis in the form of a corneal ulcer. This is a serious, potentially sight-threatening condition which causes pain, redness and light-sensitivity. It is usually treated with a course of eye drops, but can result in permanent scarring of your cornea.
Even extended wear lenses, which are designed to be worn continuously for several days, are not without their risks. Recent studies have shown a four-fold increase in the risk of infection when lenses are worn overnight, which applies whether or not your lenses are designed for extended wear.
Silicone-hydrogel materials, that allowed oxygen to pass through to the eye beneath, were the key development that gave rise to extended wear contact lenses. Prior to this, the main barrier to overnight wear was ensuring that the cornea received sufficient oxygen while the eye was closed. Studies showed that the silicone-hydrogel materials significantly reduced the incidence of harmful reactions.
However, lack of oxygen is not the only issue when considering overnight wear and doesn’t explain the increase in infections when lenses are worn overnight. It’s now thought that the space between a contact lens and the cornea, while the eye is closed for long periods, allows the development of inflammation and infection. While we’re awake we are continually blinking, sweeping a fresh film of tears across the cornea every few seconds. Obviously we don’t blink while we’re asleep, so any debris or bacteria on or behind the lens could remain there for a prolonged period.
Note: Your optician will advise you on the best type of contact lenses for your eyes, and what is a safe wearing schedule for you. Not everyone is suited to wearing contact lenses full time, or on an extended wear basis. It is essential to follow the advice given regarding the care of your lenses and to be aware of symptoms which may indicate a problem.
Even better – why not get rid of your potentially harmful contact lenses by having laser vision correction!