Disorders of the lacrimal system are among the most common problems encountered in pediatric ophthalmology. Approximately 6% of infants are born with nasolacrimal duct obstruction (NLDO). Many of these will improve spontaneously, but because NLDO is so common, lacrimal surgery is one of the most frequent surgical procedures performed by pediatric ophthalmologists.

The lacrimal system functions by producing, distributing, and eliminating tears. Tears are produced by the lacrimal gland in the superolateral orbit, flow across the eye into the lacrimal puncta, travel through the lacrimal canaliculi to the lacrimal sac, then into the nares via the nasolacrimal duct (NLD) (Figure 24–1). The contraction of the eyelid muscles creates a pumping effect, which facilitates the normal drainage of tears.

A proper tear layer is vital to ocular health for several reasons. First, the natural flow of tears continuously rinses debris and other irritants from the eyes. Second, a normal tear film is required for comfort. Patients with dry eyes have recurrent symptoms of ocular irritation. Third, the tear film is important for normal vision. The tear film is the first surface that light rays come into contact with on the eyes. A regular smooth surface is required to focus these light rays properly. If the tear film is unstable, patients experience intermittent blurred vision.

Embryology

The lacrimal drainage system begins as a nest of ectodermal cells at the site of the future lacrimal sac. Cords of cells extend from this site to the eyelids and into the nares. Canalization of this tissue results in the formation of the lacrimal sac, canaliculi, and NLD. This canalization begins at the lacrimal sac and extends distally. The last portion to canalize is the opening of the NLD into the nares.

NLDO is by far the most common lacrimal problem encountered in children, occurring in approximately 6% of infants. It results from incomplete canalization of the NLD during embryological development. Because the opening of the duct into the nares is normally the last portion to canalize, this is the most common site of obstruction (Figure 24–2).

The blocked flow of tears produces 2 clinical problems. The first is overflow tearing (epiphora). Because the tears cannot drain into the nares, they back up through the lacrimal sac and canaliculi, resulting in an increased tear lake in the eyes. This is easily conceptualized as a simple plumbing problem, with the lacrimal duct obstruction analogous to a clogged pipe. In this analogy, the resistance to flow of fluid results in collection of liquid in the sink (the normal tear layer on the eyelids), and eventually the sink overflows (epiphora).

The second clinical problem associated with NLDO is recurrent lacrimal infection. Normal flora bacteria are present in the tear film. These usually do not cause problems because they are continuously flushed from the eyes through the tear sac into the nares. However, if the tear drainage is blocked, the bacteria can accumulate in the lacrimal sac. This moist, warm environment is ideally suited to bacterial growth, and therefore recurrent infection (dacryocystitis) commonly results. The dacryocystitis that occurs in association with typical infantile NLDO is usually chronic, intermittent, and low-grade. Much less commonly, acute dacryocystitis occurs. This presents with swelling and erythema overlying the lacrimal sac.

Approximately 1% to 2% of children with NLDO will present with a mucocele (amniotocele, dacryocele, dacryocystocele). This usually is present at birth, with a distended mass overlying the lacrimal sac. Mucoceles are initially blue-tinged, but may become erythematous and inflamed if they become infected (Figure 24–3). Mucoceles are almost always associated with an NLD cyst beneath the inferior turbinate (Figure 24–4). If the cyst is large, it may cause problems with airway obstruction.

Rare embryological abnormalities of the lacrimal system include punctal or canalicular agenesis, and lacrimal sac fistulae. Punctal and canalicular agenesis results from incomplete canalization of these structures (Figure 24–5). Because the tears have nowhere to drain, these children present with epiphora. Lacrimal sac fistulae result from aberrant cords of tissue that extend from the lacrimal sac to the skin, typically between the eye and the nares. If the fistulae are patent, tears may flow through them, producing epiphora (Figure 24–6). Crocodile tears are an unusual disorder in which aberrant innervation of the lacrimal gland causes tearing to occur during chewing or swallowing (Figure 24–7).

Dry eyes result from abnormal tear production. This is a relatively uncommon problem in children. There are 2 types of tears. The first are basal tears, which are important for maintaining ocular health and clear vision. Absence or reduction of basal tear production (alacrima) is rare. It may occur in conditions such as Riley-Day syndrome (familial dysautonomia) or graft-versus-host disease. The second type of tears are reflex tears, which are produced in response to either irritiation or emotional stimuli. These tears are produced when someone is crying. Some infants do not produce reflex tears. This does not cause vision problems because the basal tears function normally.