LACRIMAL SECRETORY SYSTEM

The largest volume of tear fluid is produced by the major lacrimal gland located in the lacrimal fossa in the superior temporal quadrant of the orbit. This almond-shaped gland is divided by the lateral horn of the levator aponeurosis into a larger orbital lobe and a smaller palpebral lobe, each with its own ductule system emptying into the superior temporal fornix (Chapter 1). The palpebral lobe can sometimes be visualized by everting the upper lid. The secretions from the main lacrimal gland are triggered by emotion or physical irritation and cause tears to flow copiously over the lid margin (epiphora). Innervation of the main gland is from the pontine lacrimal nucleus through the nervus intermedius and along an elaborate pathway of the maxillary division of the trigeminal nerve. Denervation is a common consequence of acoustic neuroma and other tumors of the cerebellopontine angle.

The accessory lacrimal glands, although only one-tenth the mass of the major gland, have an essential role. The glands of Krause and Wolfring are identical to the major gland but lack a ductile system. These glands are located in the conjunctiva, mainly in the superior fornix. Unicellular goblet cells, also scattered throughout the conjunctiva, secrete glycoprotein in the form of mucin. Modified sebaceous meibomian and zeisian glands of the lid margin contribute lipid to the tears. The glands of Moll are modified sweat glands that also add to the tear film.

The accessory glands are known as the "basic secretors." Their emissions are sufficient to maintain the cornea without those of the main lacrimal gland. Loss of goblet cells, however, leads to drying of the cornea despite profuse tearing from the lacrimal gland.

DISORDERS OF THE SECRETORY SYSTEM

Alacrima

Congenital absence of tearing occurs in Riley-Day syndrome (familial dysautonomia) and anhidrotic ectodermal dysplasia. Although initially asymptomatic, patients may develop signs typical of keratoconjunctivitis sicca. Absence of tears may also occur after disruption of the lacrimal secretory nerve by acoustic neuroma or following surgery of the cerebellopontine angle. Tumors or inflammation of the lacrimal gland may reduce tear production.

Lacrimal Hypersecretion

Primary hypersecretion is rare and must be distinguished from tearing due to obstruction of the excretory ductules. Secondary hypersecretion may be psychogenic or reflex from irritation of surface epithelium or retina. It is possible to stop hypersecretion by blocking the lacrimal secretory nerve in the sphenopalatine ganglion.

Paradoxic Lacrimation ("Crocodile Tears")

This condition is characterized by tearing while eating. Although it may be congenital, it is usually acquired after Bell's palsy and is the result of aberrant regeneration of the facial nerve.

Bloody Tears

This is a rare clinical entity attributed to a variety of causes. It has been associated with menstruation ("vicarious menses"). Blood-tinged tears may be secondary to conjunctival hemorrhage due to any cause (trauma, blood dyscrasia, etc) or to tumors of the lacrimal sac. They have also been reported in a hypertensive patient suffering from epistaxis with extension through the nasolacrimal duct.

Dacryoadenitis

Acute inflammation of the lacrimal gland is a rare condition most often seen in children as a complication of mumps, measles, or influenza and in adults in association with gonorrhea. Chronic dacryoadenitis may be the result of benign lymphocytic infiltration, lymphoma, leukemia, or tuberculosis. It is occasionally seen bilaterally as a manifestation of sarcoidosis. When combined with parotid gland swelling, it is called Mikulicz's syndrome.

Considerable pain, swelling, and injection occur over the temporal aspect of the upper eyelid, which often imparts to it an S-shaped curve. If bacterial infection is present, systemic antibiotics are given. It is rarely necessary to surgically drain the infection.

10.1036/1535-8860.ch4

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