The mucin layer, closest to the eye's surface, is made in the eyelid and on the surface of the eye; the aqueous or watery middle layer is made in the lacrimal gland above the eye; and the oily, top layer is made in the meibomian gland in the eyelid.
22.
Dr . David A . Sullivan, an associate professor of ophthalmology at the Schepens Eye Research Institute at Harvard, attributes the aging factor in men and women partly to a decrease in the production of androgens like testosterone, needed for normal function of the Meibomian glands, which regulate the evaporation of tears.
23.
Along the inner margin of the tarsus are modified sebaceous glands known as tarsal glands ( or meibomian glands ), aligned vertically within the tarsi : 30 to 40 glands in the upper lid, and 20 to 30 in the lower lid, which secrete a lipid-rich product which helps keep the lacrimal secretions or tears from evaporating too quickly, thus keeping the eye moist.
