Figure 1-3. The lacrimal apparatus.
(2) Conjunctiva. The conjunctiva covers the inner surface of the eyelids and
the outer surface of the eyeball. Lacrimal fluid keeps the conjunctiva transparent. With
the blink reflex, the lacrimal fluid washes away any foreign particles that may be on the
surface of the conjunctiva.
(3) Eyelid oil glands. The free margins of the upper and lower eyelids have
special oil glands. The oily secretion of these glands helps prevent the lacrimal fluid
(4) Lacrimal fluid. With the movement of the eyeball and the eyelids, the
lacrimal fluid is gradually moved across the exterior surface of the eyeball to the medial
inferior corner. Here, the lacrimal fluid is collected into a lacrimal sac, which drains into
the nasal chamber by way of the nasolacrimal duct. Thus, the continuous production of
lacrimal fluid is conserved by being recycled within the body.
PHYSIOLOGY OF VISION
For vision to occur, light must pass through the cornea, aqueous humor, pupil,
lens, and vitreous humor before it (light) can reach the rods and cones. Light reaches
the rods and cones of the retina and forms an image on the retina. Next, nerve
impulses are conducted to the visual areas of the cerebral cortex (a part of the brain).