We blink our eyes regularly to maintain this complicated layer. It lubricates the eye and lid movements and provides the clear corneal surface that makes vision possible to mention only two of its many functions. If the tearfilm does not function properly, dry spots develop producing friction between the eye surface and the lid which causes grittiness, burning, tearing etc. Increased friction between eye and lid makes the eye and lid muscles work harder causing them to ache and the lids to droop. Watery tears are produced in response to emotional disturbance and irritations and has a detrimental effect on the function of the tearfilm.
Contact lenses require more tears and people with dryness tendencies often become symptomatic.
Dryness is the most common reason for contact lens failure. Our genes some people have the tendency towards dry or oily skin or hair. They were born that way. The same applies to our eyes. Rubbing the eyes disturbs the delicate three-layered stucture of the tearfilm and causes it to break up forming dry spots.