Mucoaqueous

Three distinct layers of the tear film are recognized. A thin layer of lipid or fatty substances covers the aqueous or mucoaqueous portion.[…]FIG. 1. The three layers of the tear film. Although the thin lipid layer is well defined, the mucoaqueous and mucoid layers are continuous, with the bulk of the mucin concentrated near, and adhering to, the epithelial microprojections.

To encompass the entirety of the tear film, composed of the interpalpebral and retropalpebral portions, the neologism ‘dacruon’ was termed (Cher 2007, 2008). The dacruon represents the mucoaqueous layer and lipid sealant of the interpalpebral portion of the tear film as well as the opposing mucoaqueous reservoirs of the palpebral and conjunctival surfaces in the retropalpebral portion, which lacks an outer lipid layer.

Fig. 127.2 Schematic representation of the tear film architecture (based on a novel model proposed by the International Meibomian Gland Dysfunction Workshop 2011).[…]The mucoaqueous component delivers essential nutrients (carbohydrates, proteins, enzymes, vitamins, hormones) to the ocular surface and the avascular structures of the external eye.

Another way the tear film may be conceptualized is as a 2 layer system. The inner layer is made up of a combination of the mucus and aqueous layers to form a mucoaqueous gel layer. The outer second layer is the lipid layer.