3.6.2 Why is there a limit to the length of wearing time ?
Description
This article is from the Vision and Eye Care FAQ, by grants@research.canon.com.au (Grant Sayer) with numerous contributions by others.
3.6.2 Why is there a limit to the length of wearing time ?
The cornea the "clear part of the eye", is avascular or without a blood supply.
It is avascular otherwise it wouldn't transmit light without distortion.
As a result of this living tissue being avascular it is necessary to
obtain oxygen from the atmosphere. The wearing of a contact lens interrupts
the flow of oxygen to the cornea and due to changes in the metabolic pump of
the corneal cells the tissue thickens, called oedema.
Contact lenses, as described in Section XXX, are manufactured from material
that allows maximum oxygen transmission. But this is still not exactly the
same as the 20.4% therefore the lens wearing time must be controlled to
reduce oxygen deprivation to the cornea.
Continue to:
My Books
