During blinking tears form a film which coats, protects and nourishes the eye surface. When the tear volume is reduced or the tear film is unstable, eyes can fill gritty, scratchy and irritated.
Anything that reduces the normal amount of tears may result in dry eye.
The tear film is a trilaminate structure, which protects the surface of the eye, helping to create a smooth optical surface so vision stays crisp, clear and undistorted.
LIPID LAYER is composed of oils secreated by the meibomaian glands. This is
the outermost layer of the tear film covering the aqueous phase and providing
a hydrophobic barrier, which modulates tear evaporation and retains moisture.
The lipid layer also protects the eye surface from contamation.
AQUEOUS LAYER is produced by
the lacrymal gland it is the central component of the tear film
and accounts for about 98% of tear volume. It consists mainly of
water but also contains other substances such as proteins, which
nourish the eye, and electrolytes. This layer also washes away
irritants, keeping the eye healthy. It helps maintain optimum vision
by promoting spreading of the tear film across the cornea.
