The Tear Film

This film, which bathes the eye, is actually a complex structure composed of 3 layers. The innermost mucin layer is secreted by the goblet and epithelial cells of the conjunctiva and the acinar cells of the lacrimal gland. It adds stability and provides an attachment for the tear film to the conjunctiva and cornea. The middle aqueous layer constitutes 98% of the tear film and is produced by the main lacrimal gland and accessory lacrimal glands. It contains various electrolytes and proteins as well as antibodies. The outermost lipid layer is produced largely from the sebaceous meibomian glands of the eyelid and retards evaporation of the tear film. Tears drain medially into the punctal openings of the lid margin and flow through the canaliculi into the lacrimal sac and then through the nasolacrimal duct into the nose. Preterm infants have reduced tear secretion. This may mask the diagnosis of a nasolacrimal duct obstruction and concentrate topically applied medications. Tear production reaches adult levels near term.

Dacryostenosis

Congenital nasolacrimal duct obstruction (CNLDO), or dacryostenosis, is the most common disorder of the lacrimal system, occurring in up to 6% of newborn infants. It is usually caused by a failure of canalization of the epithelial cells that form the nasolacrimal duct as it enters the nose (valve of Hasner). Signs of CNLDO may be present at the time of birth, although the condition may not become evident until normal tear production develops. Signs of CNLDO include an excessive tear lake, overflow of tears onto the lid and cheek, and reflux of mucoid material that is produced in the lacrimal sac. Erythema or maceration of the skin may result from irritation and rubbing produced by dripping of tears and discharge. If the blockage is complete, these signs may be severe and continuous. If obstruction is only partial, the nasolacrimal duct may be capable of draining the basal tear film that is produced. However, under periods of increased tear production (exposure to cold, wind, sunlight) or increased closure of the distal end of the nasolacrimal duct (nasal mucosal edema), tear overflow may become evident or may increase.

Infants with CNLDO may develop acute infection and inflammation of the nasolacrimal sac (dacryocystitis), inflammation of the surrounding tissues (pericystitis), or rarely periorbital cellulitis. With dacryocystitis, the sac area is swollen, red, and tender, and patients may have systemic signs of infection such as fever and irritability.

The primary treatment of uncomplicated nasolacrimal duct obstruction is a regimen of nasolacrimal massage, usually 2-3 times daily, accompanied by cleansing of the lids with warm water. Topical antibiotics are used for control of mucopurulent drainage. A bland ophthalmic ointment may be used on eyelids if the skin is macerated. Most cases of CNLDO resolve spontaneously; 96% before 1 yr of age. For cases that do not resolve by 1 yr, the nasolacrimal duct may be probed, with a cure rate of approximately 80%. Some ophthalmologists intubate the nasolacrimal system at the same time because this has been shown to improve the outcome of the procedure.

Acute dacryocystitis or cellulitis requires prompt treatment with systemic antibiotics. In such cases, some form of definitive surgical intervention is usually indicated.

A dacryocystocele (mucocele) is an unusual presentation of a nonpatent nasolacrimal sac that is obstructed both proximally and distally. Dacryocystoceles can be seen at birth or shortly after birth as a bluish subcutaneous mass just below the medial canthal tendon (Fig. 617-1). Initial treatment of dacryocystocele is usually conservative, involving massage/digital decompression of the lacrimal sac. If resolution of the dacryocystocele is not achieved with conservative management, the surgical probing may be beneficial. At times, the intranasal portion of the nasolacrimal duct becomes distended causing respiratory compromise. In a recent study, 9.5% of infants with dacryocystocele had related respiratory compromise. These infants benefit from early probing. Another associated complication of dacryocystocele is that of dacryocystitis/cellulitis. This requires systemic antibiotics, often with hospitalization. In the aforementioned study, 65% of infants with dacryocystocele developed dacryocystitis/cellulitis. Once the cellulitis has improved, the nasolacrimal system should be probed if spontaneous resolution has not occurred.

Figure 617-1 Dacryocystocele below inner canthus of the right eye.

Not all tearing in infants and children is caused by nasolacrimal obstruction. Tearing may also be a sign of glaucoma, intraocular inflammation, or external irritation, such as that from a corneal abrasion or foreign body.

Alacrima and “Dry Eye”

Alacrima refers to a wide spectrum of disorders with reduced or absent tear secretion. Occasionally, normal basal tearing occurs with an absence of emotional tearing. Etiologies can be divided into syndromes, pathologic association or inherited. Associated syndromes include familial dysautonomia (Riley-Day syndrome), anhidrotic ectodermal dysplasia, triple-A syndrome (Allgrove syndrome). Examples of pathologic association include aplasia of cranial nerve nuclei and lacrimal gland aplasia/hypoplasia. Both autosomal recessive and autosomal dominant inheritance has been reported in isolated congenital alacrima. The patients with alacrima have variable presentation including no symptoms, photophobia, foreign body sensation, eye pain, and decreased vision. The symptoms, if present, often occur early in life. Because the dryness can be severe, damage to the cornea and subsequently loss of vision may occur. The goal of treatment is to minimize corneal irritation, corneal scarring, and loss of vision. Aggressive ocular lubrication is used to prevent these sequelae.

An acquired abnormality of any layer of the tear film may produce a dry eye. Commonly acquired disorders that may lead to a decreased or unstable tear film include Sjögren syndrome, Stevens-Johnson syndrome, vitamin A deficiency, ocular pemphigoid, trachoma, chemical burns, irradiation, and meibomian gland dysfunction. Any tear deficiency can lead to corneal ulceration, scarring, or infection. Treatment includes correction of the underlying disorder when possible and frequent instillation of an ocular lubricant. In some cases, occlusion of the lacrimal puncta is helpful. In severe cases, tarsorrhaphy may be necessary to protect the cornea.