-Mucin, a hydrated glycoprotein, makes up the deepest tear layer (1 - 2 um thick). --> fills in any irregularities of the corneal surface, thereby providing a smooth ocular surface.
1. Orbital gland (main source in dogs)
2. Gland of third eyelid (nictitating membrane)
3. Harderian gland
-secrete the AQUEOUS component of tears: intermediate layer < 7 um thick, accounts for most of total tear volume & consists of water, electrolytes, glucose, urea, surface-active polymers, glycoproteins, & tear proteins (lactoferrin & some serum proteins - IgA, albumin, & lysozyme)
1. Meibomian (Tarsal) glands - most important
2. Glands of Zeis
-thin (0.1 um) superficial lipid layer provides a thin, oily covering over the aqueous tear layer --> prevents evaporation & promotes a stable, even spread of tears over the cornea.
EPISCLERAL Injection (hyperemia)
Conjunctival hyperemia = general response of conjunctiva to disease
Episcleral injection, which occurs w/ glaucoma & anterior uveitis.
PHENYLEPHRINE drop on eye --> Conjunctiva vessels blanch right away. Episcleral vessels require ~10 min. to blanch.
deficiency in aqueous tears --> desiccation (extreme dryness) & inflammation of conjunctiva & cornea, ocular pain, progressive corneal dz., & reduced vision.
(in image, note the horrible film of mucin that is just sticking to the cornea)
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