TEAR FILM ABNORMALITIES:

1.Mucus starands and debris are an early sign . In the normal eye, as the tear film breaks down,the mucin layer becomes contaminated with lipid but is washed away . In the dry eye ,the lipid-contaminated mucin accumulates in the tear film and tends to move with each blink. Mucin also has the interesting property of drying very quickly and rehydrating very slowly.
2. The marginal tear meniscus is a crude measure of the volume of aqueous in the tear film. The normal meniscus varies in height between 0.1 and0.5 mm and forms a convex band with a regular upper edge . In KCS the tear meniscus becomes concave,irregular,thin or absent.
3. Froth in the tear film or along the eyelid margin occurs in meibomian gland dys function.