The ocular surface comprising the cornea and conjunctiva must maintain adequate hydration for optical transparency and refractivity. Tear film covers the ocular surface, providing lubrication and nutrition while protecting against desiccation [1]. Tears are secreted by the lacrimal glands and distributed by blinking and drainage through the lacrimal apparatus [1][3]. The aqueous layer is secreted by accessory lacrimal glands and goblet cells [4].

Aqueous humor provides additional fluid input, produced by the ciliary processes and draining into the anterior chamber [4]. Drainage occurs via the trabecular meshwork or uveoscleral pathways, balancing production to maintain intraocular pressure [2][3]. The corneal endothelium actively transports solutes to prevent swelling from excess fluid. Any imbalance in tear film, aqueous humor dynamics or endothelial function can disturb ocular surface hydration, compromising visual function [3][4].

Sources:

1, 2,. Mason, P. (2011). Medical neurobiology. Oxford University Press.
3, 4. Goldstein, E.B. (Ed.). (2015). Encyclopedia of perception. Sage Publications.