The lacrimal system includes the lacrimal gland, upper and lower lid puncta, upper and lower lid canaliculus, lacrimal sac, and nasolacrimal duct. The lacrimal gland is responsible for the production of the middle (aqueous) layer of the tear film. It is innervated by the lacrimal branch of the middle division trigeminal nerve. The superficial layer of the tear film is contributed by the meibomian glands of the lids (see Chapter 2: Lids and Adnexa). The inner layer of the tear film is made by the conjunctival goblet cells (see Chapter 4: Conjunctiva). As the tear film is produced continuously, it must have a place to drain. The nasolacrimal system collects the tears via the puncta, which must be patent and lie in apposition to the surface of the globe so that they may collect the tear film drainage. If there is inadequate drainage, epiphora will occur. Flow of tears into the nasolacrimal system is facilitated by the orbicularis muscle and other muscles surrounding the sac creating a pumping mechanism. If the lids are hypotonic, malpositioned, or floppy (see Chapter 2: Lids and Adnexa), epiphora may result as the tears are unable to gain access to the puncta.

Each punctum lies at the peak of an elevated papilla. There is a vertical path of approximately 2 mm followed by a 90-degree turn into the canaliculus. The upper and lower canaliculi join at the medial canthus to form the common canaliculus, which then enters the lacrimal sac. The lacrimal sac is located in a bony sulcus in the anterior medial orbital wall such that only its upper third is exposed. The remainder of the sac and the nasolacrimal duct lie within the bone of the anterior orbit and face. The nasolacrimal duct opens into the nose as the inferior meatus under the ipsilateral inferior turbinate. Disease within the nose may also cause obstruction.

Although nasolacrimal system abnormalities are commonly isolated, they may also be seen in a wide variety of syndromes, particularly those that affect midline disorders or the lids. Dysfunction can also occur secondary to trauma, tumor, and infection. Likewise, the lacrimal gland can be affected by infection, tumor, or external influences such as radiation. Lacrimal gland dysfunction may also occur in Sjögren and other autoimmune diseases (see Chapter 27: Rheumatology). Dysfunction of the lacrimal gland results in dry eye.