Overnight Wear
Lenses
Too much hassle to take your lenses out at
night ? Then why not change to lenses that you can sleep in.
OVERNIGHT WEAR LENSES CAN BE WORN
CONTINUOUSLY, WITH JUST A NIGHT OFF ONE DAY A MONTH BEFORE STARTING
THE NEW PAIR.
How Are These Lenses Different?
They let through a lot more oxygen to the cornea – up to 6 times
more.
Why Is This Necessary?
The cornea like all other tissues in the body requires a continuous
supply of oxygen. Because it has no blood vessels of its own, it gets
its supply directly from the air – oxygen from the air dissolves
into the tear layer.
When the eyes are closed, no direct air transfer is possible. Instead
oxygen diffuses across from the blood vessels that line the inside
of the eyelids. This night time supply is much lower than the daytime
one because there is less oxygen in the blood than in air. A contact
lens reduces the supply further as it is a barrier through which some
of the oxygen molecules don’t get through.
Overnight wear lenses incorporate
Silicone which makes the lenses much more oxygen permeable.
These lenses are also good for people
who don’t want to wear their lenses overnight but who have very
long daily wearing times. They have also been fitted on those individuals
whose corneas have shown signs of oxygen deprivation in the past,
and those whose eyes just have a naturally higher oxygen requirement. |
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