Your eyelids contain 45–70 tiny oil-secreting glands called meibomian glands. Every blink, they release a lipid layer — a thin film of oil — that sits on top of the tear film and stops it evaporating. When these glands are blocked or under-functioning, that lipid layer thins or disappears entirely. The tear film evaporates between blinks. The cornea — one of the most densely innervated tissues in the human body — is exposed to air repeatedly, every few seconds.
That constant low-level exposure is what burning feels like. It is not tiredness. It is not strain. It is a specific sensory signal from corneal nerve endings responding to a surface that should be protected and isn't. The sensation is real, the cause is mechanical, and the fix is equally mechanical: restore the lipid layer by restoring the glands that produce it.