These two glands work in sync to produce and stabilize your tear film so that you can see clearly at all given times.
The tear film is made of 3 layers
The lipid layer prevents evaporation of the Aqueous layer. The innermost mucin gives a base to the Your involuntary blinking action of your lids – about 4-6 times a minute helps lubricate, coat and protect the surface of your eyes
The closing of your lids, help squeeze the Meibomian glands to secrete the lipid layer. This inturn impact the smooth movement of your eye lids.
So, every time you blink, it acts as a wiper – lubricates and cleans your eye of any dirt particles.
If the constitution of either of these 3 layers is altered, then the tear film break up time and the viscosity of the tear film changes, giving rise to: