Why Dry Eyes Water

The film covering your eye is a three-layer structure a few microns thick. Beneath is a mucin layer that allows tears to adhere to the corneal surface. In the middle is the aqueous layer, produced by the lacrimal gland — the part most people picture when they think of tears. On top, and most often the culprit, is a microscopically thin oil layer secreted by the meibomian glands within the eyelids.

That oil layer has one job: to stop the aqueous layer evaporating. When it fails, tears evaporate within seconds of a blink rather than lasting the ten or more seconds they should. The surface is left exposed, and the cornea — one of the most densely innervated tissues in the body — registers this immediately.

An irritated cornea triggers a reflex arc that instructs the lacrimal gland to flood the eye. The tears it produces arrive quickly and in volume, but they are almost purely aqueous. They have no oil layer to hold them in place and no time to spread properly. So they pool, spill over the lid margin, and run down the cheek.

The patient experiences streaming eyes. The eye, meanwhile, is still dry — it is producing the wrong tears, at the wrong moment, in the wrong composition. Treating this with more artificial tears alone is a little like adding water to a leaking bucket.

This city assembles almost every risk factor at once. Ambient humidity outdoors is low for much of the year. Indoors, air-conditioning runs continuously and drives humidity lower still, with constant airflow across the face in cars and offices. Add fine airborne dust, long screen hours — which reduce blink rate by up to sixty per cent — and widespread contact lens use, and the meibomian glands are under sustained pressure.

Blinking matters more than most people realise. A complete blink is what expresses oil from the glands onto the tear film. During concentrated screen work, blinks become fewer and, crucially, incomplete: the upper lid does not fully meet the lower. The glands are not emptied, their contents thicken, and over months the glands themselves begin to shorten and drop out. On infrared imaging this is visible directly, and it is not reversible.

Dry eye is rarely cured outright, but it is very frequently controlled — and control usually begins the moment the diagnosis becomes specific rather than general. If your eyes water, that is a symptom worth investigating properly, not a reason to rule dryness out.