Tearing, when excessive tears pool on the ocular surface, and epiphora, when tears overrun the ocular margin and pour down onto the face, occur if there is either overproduction or insufficient drainage of tears. Although tearing and epiphora may seem trivial, they cause significant morbidity and patient discomfort, interfering with daily activities such as driving and reading, causing periocular skin irritation and infection, as well as disruption in social interactions. Appropriate treatment and resolution of tearing may be challenging, and determining the appropriate course of action requires a detailed history, careful examination of the eye and lacrimal system, and experience in deciding which medications or procedures will alleviate the problem. In this chapter, we review the normal anatomy and physiology of the lacrimal system, discuss the relevant examination and testing, and conclude with the currently available treatments and their indications.

2.2 Anatomy of Tear Production

Tears are produced by both the lacrimal gland and accessory lacrimal glands. There is a basal production rate of approximately 1.2 μL/min, which may increase by over 500% when reflex or emotional tearing are triggered by ocular irritants or emotional states. ¹

2.2.1 Lacrimal Gland

The lacrimal gland is responsible for producing over 90% of the tear volume. It is located in the anterior superotemporal orbit and is composed of two lobes: the palpebral lobe (smaller, more anterior and inferior) and the orbital lobe (larger, more posterior and superior; ▶ Fig. 2.1). This gland is composed of secretory acini, which empty tears into 8 to 12 major ducts. The lacrimal gland is innervated by both cranial nerve (CN) V and CN VII, which form part of the reflex tearing arc, as well as by parasympathetic and sympathetic nerve fibers. ^{2,​ 3}

2.2.2 Accessory Lacrimal Glands

The accessory lacrimal glands of Krause and Wolfring are nearly identical in structure to the main lacrimal gland; however, they are smaller and are klocated within the substantia propria of the conjunctiva. There are approximately 20 glands of Krause in the superior conjunctival fornix and 6 to 8 in the lower fornix. Approximately 3 glands of Wolfring are found along the superior border of the upper tarsus. ⁴

2.2.3 Anatomy of Tear Drainage

Once produced, tears are spread across the ocular surface via the normal blink mechanism. Normal blink and eyelid tension is essential in preventing both dryness of the ocular surface and pooling of tears. Tears then flow toward the medial canthus, where the lacrimal drainage is initiated ( ▶ Fig. 2.2). ²

2.2.4 Puncta

Each eyelid margin has a small conical protrusion at its medial end, the lacrimal papilla, on which there is a small opening approximately 0.3 mm in diameter, the lacrimal punctum ( ▶ Fig. 2.2). The normal punctum faces inward toward the globe to be in contact with the tear film. Ectropion of the punctum or stenosis of the punctum prevents the normal outflow of tears and leads to pooling on the ocular surface. ^{5,​ 6}

2.2.5 Canaliculi

From the puncta, the tears enter the canaliculi, which are thin tubes surrounded by fibrous tissue and orbicularis muscle. The canaliculi carry tears medially toward the nasolacrimal sac. There is an upper canaliculus and a lower canaliculus ( ▶ Fig. 2.2). Both are first oriented vertically for approximately 2 mm, and widen at the base to form an ampulla, and bend medially at a right angle to continue horizontally for 8 mm. In most patients (90%), the upper eyelid and lower eyelid canaliculi join to form a common canaliculus for 1 to 2 mm prior to entering the nasolacrimal sac. ^{5,​ 6}

2.2.6 Lacrimal sac

The tears pass from the canaliculi into the lacrimal sac. The lacrimal sac sits within the lacrimal sac fossa, formed anteriorly by the frontal process of the maxillary bone and posteriorly by the lacrimal bone, which create the anterior and posterior lacrimal crests, respectively. The lateral and superolateral aspects of the lacrimal sac are not surrounded by bone. Surrounding the lacrimal sac are medial fibers of the orbicularis oculi muscle that become the medial canthal tendon. The anterior fibers are known as the muscle of Riolan, and the posterior fibers (inserting onto the posterior lacrimal crest) are known as Horner’s muscle. Due to the strength of the medial canthal tendon, and relative weakness of the fascia inferior to it, enlargement of the lacrimal sac, as in dacryocystitis, typically results in swelling below the medial canthal tendon ( ▶ Fig. 2.3). The lacrimal sac is approximately 12 to 15 mm in height and about 4 mm in diameter, although it is generally empty and flat. ⁵

2.2.7 Nasolacrimal Duct

The lacrimal sac narrows and becomes the nasolacrimal duct as it traverses inferiorly in a posterior-inferior-lateral direction. The duct travels through a bony canal in the maxillary bone and narrows to 1 mm in diameter. The duct then empties into the lateral nasal wall of the inferior meatus, below the inferior turbinate. The duct is approximately 18 mm long. At the end of the duct, there is a small flap of valve-like mucosa called the valve of Hasner. ⁵

2.2.8 Nasal Anatomy

Normally tears exit the nasolacrimal duct into the inferior meatus. However, when a surgical fistula is made, as in dacryocystorhinostomy (DCR) surgery, this occurs in the middle meatus ( ▶ Fig. 2.4). Protecting this meatus is the middle turbinate, whose anterior end is a key landmark during lacrimal surgery. Other important intranasal landmarks include the maxillary line and the uncinate process. The maxillary line is a vertical elevation of mucosa formed by the underlying frontal process of the maxilla ( ▶ Fig. 2.5). This generally corresponds to the anterior portion of the nasolacrimal duct. The uncinate process is a smooth mucosal elevation in the anterior middle meatus. Usually, the lacrimal duct is located anterior and lateral to the uncinate process. ^{3,​ 5}

2.3 Physiology of the Lacrimal System

2.3.1 Tear Composition

The tear film is composed of three layers. The deepest layer is the mucin layer, which is formed by the goblet cells of the conjunctiva. The mucin acts as a lubricant, a surfactant to stabilize the tear film, and a trap for debris and bacteria. The middle layer of the tear film is the aqueous layer, which is the thickest layer. It contains electrolytes, glucose, oxygen, immunoglobulins (IgA, IgM, IgD, IgE, and IgG), as well as antimicrobial proteins such as lysozyme, lactoferrin, lipocalins and defensins, cytokines, and growth factors. These factors are necessary for maintenance and nutrition of the corneal cells, as well as protection from infectious agents. The most superficial layer is a lipid layer, which is formed by the Meibomian glands. The lipids limit tear evaporation and increase surface tension to retard epiphora. ¹

2.3.2 Blink Mechanism

Drainage of tears depends on a normal blink of the eyelids. A combination of positive and negative pressures generated by the contraction of the orbicularis oculi muscle concurrently push the tears from the ocular surface and pull them down the drainage system. Dysfunction of the orbicularis oculi, as in facial nerve palsy, results in poor tear drainage because of absence of this pump function. Closure of the eyelids increases pressure on the lacrimal sac and propels tears down the duct and into the nose. When the eyelids open, negative pressure within the now empty canaliculi draws new fluid into the canaliculi in preparation for the next blink. ^{2,​ 3,​ 5}

2.3.3 Evaporation

Evaporation accounts for approximately 10% of tear loss in the young and up to 20% in the elderly. Abnormal lipid production and insufficient coating of the aqueous layer, low ambient humidity, and air movement/wind can increase the rate of evaporation and dryness on the ocular surface. Excessive dryness leads to ocular irritation, which triggers reflex tearing. ²

2.4 Tearing or the Watery Eye

Patients may suffer immensely from tearing or epiphora. They may have almost constant blurry vision, irritation of the eyelid skin or the eye, and embarrassment when other people inquire about their “crying.” Although a singular complaint, the etiology of tearing is varied, making the diagnosis challenging and requiring a careful history, detailed examination, and often testing ( ▶ Table 2.1). One main point to distinguish on history and examination is whether the patient is suffering from epiphora due to obstruction of tear outflow, or from excess tear production (reflex tearing) triggered by dry eye conditions. Patients with tearing may complain of irritation, ocular discomfort, intermittent blurry vision, eye pressure, eye fatigue, and photosensitivity, all symptoms that point toward ocular surface dryness and reflex tearing. Patients may also complain of tears running down their cheeks that require frequent wiping with a tissue, skin irritation, and worsening of tearing in windy conditions, all of which may point to inadequate tear drainage. It is useful to ask patients about the duration of their symptoms, time of day when they occur, exacerbating and alleviating factors, severity of symptoms, and frequency of symptoms. One may gauge the severity of tearing by asking the patient how many times per day he or she needs to wipe the eyes with a tissue. Symptoms produced by various underlying conditions may overlap significantly and therefore a careful history as well as examination is essential ( ▶ Table 2.1). A baseline slit-lamp examination is critical in this evaluation, and office testing may be useful to further elucidate the underlying etiology. ^{2,​ 3,​ 5,​ 7,​ 8}

2.4.1 Office Testing

The most common office test performed is irrigation of the lacrimal system with saline. Various dye tests have also been described, but are used less frequently in clinical practice than irrigation.

 Dye Disappearance Testing

This is a simple test to noninvasively assess the functional patency of the nasolacrimal system. One drop of 2% fluorescein is instilled into each inferior conjunctival fornix. The eyes are examined with a cobalt blue light for persistence of dye after 5 to 10 minutes. With normal tear drainage, there should be no detectable dye remaining after 10 minutes. The persistence of dye, sometimes with an elevated tear lake, may suggest either an obstructed drainage system or a functional (physiologic) abnormality limiting flow. ^{2,​ 3,​ 5}

 Jones’ Testing

Jones’ testing involves instillation of 2% fluorescein into the conjunctival fornix and retrieval of fluid from the nose to evaluate for patency of the tear drainage system. While historically noted, this is rarely performed in the modern era. ^{2,​ 3,​ 5}

 Irrigation

Nasolacrimal irrigation is perhaps the most important test to evaluate the patency of the nasolacrimal system. It is not a functional test, as nonphysiologic conditions are created by irrigating the system with a cannula. The pressure generated in irrigation may overcome lesser stenoses and blockages that may otherwise cause symptoms. Proparacaine or other topical anesthetic eyedrops are instilled into the eye to be tested. For further anesthesia, a pledget with topical anesthetic is placed over the inferior punctum for several minutes prior to irrigation. The punctum (generally the lower eyelid) is dilated with a punctal dilator, following the natural course of the canaliculus. The punctal dilator is inserted vertically for 2 mm into the punctum, after which the lower lid is distracted laterally and the dilator is rotated 90 degrees into the horizontal position and advanced medially to dilate the punctum. Next, a lacrimal cannula attached to a 3-mL syringe filled with water or saline is used to cannulate the punctum and canaliculus. It is advanced until a hard stop is achieved, that is, a stoppage of the cannula against a rigid structure without movement of the surrounding soft tissues, as in encountering the lacrimal bone. Any stenosis or complete blockage of the punctum or canaliculus should be noted. When these are present, a soft stop is encountered, that is, a stoppage of the cannula that drags the surrounding soft tissue. Then, using minimal force on the plunger, liquid is flushed through. Easy and complete passage of liquid through the system and into the nose without any reflux of liquid out the puncta confirms patency. More difficult passage or reflux suggests stenosis or obstruction. If saline refluxes back through the same canaliculus, a canalicular obstruction or stenosis is present, in which case the upper canaliculus should be tested. If there is an obstruction at the common canaliculus or nasolacrimal duct/sac, reflux through the upper punctum will be seen when irrigation is performed through the lower punctum ( ▶ Fig. 2.6). If the refluxed fluid is mucoid, it suggests that there is a nasolacrimal duct obstruction (NLDO) below the nasolacrimal sac. If there is partial irrigation through the system and partial reflux through the opposite canaliculus, it suggests partial obstruction. ^{2,​ 3,​ 5}

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