Nasolacrimal duct obstruction

ETIOLOGY

Approximately 6% of all neonates have nasolacrimal duct obstruction.2 The number is as high as 75% when fetal autopsies are performed. The most common etiology is failure of the valve of Hasner to open. The valve of Hasner is located at the distal end of the nasolacrimal duct where it enters the inferior meatus lateral to the inferior turbinate. The nasolacrimal duct normally canalizes from proximal to distal, so the distal end is often last to open. Thus, premature infants probably have much higher rates of nasolacrimal duct obstruction. However, because tear production does not occur until near term, these infants often do not exhibit the symptoms of epiphora.

CLINICAL PRESENTATION AND DIAGNOSIS

Most infants present with tearing and/or mattering of the involved eye. Depending on the level of obstruction, the symptoms may be more tearing than mattering or vice versa (232). Mucopurulent discharge can sometimes be expressed from the lacrimal sac through the punctum with digital massage. Symptoms are often worse in the cold or wind, or when the child has an upper respiratory infection.

The presentation may be unilateral or bilateral. There is usually not concurrent conjunctival injection, which differentiates it from more typical conjunctivitis.

The diagnosis of nasolacrimal duct obstruction is a clinical one. One must be diligent in looking for other, less common causes of tearing. The most important diagnosis on the differential is infantile glaucoma. Increased intraocular pressure (IOP) can lead to corneal epithelial edema and breakdown, resulting in tearing. Other signs and symptoms consistent with infantile glaucoma include increased corneal diameter, optic nerve cupping, photophobia, and increased axial length resulting in myopia. The combination of epiphora with any of these other signs or symptoms should lead one to consider the diagnosis of infantile glaucoma. Other causes of infantile epiphora include keratitis, foreign body, or agenesis of the lacrimal puncta. The dye disappearance test can be used to assess the presence of nasolacrimal duct obstruction. One drop of fluorescein is placed into each conjunctival sac. After 5 minutes, the conjunctival tear lake is assessed using cobalt blue light. The normal infant will not have fluorescein remaining in the conjunctival sac, whereas the infant with nasolacrimal duct obstruction will show a varying amount of fluorescein depending on the degree of stenosis.1

MANAGEMENT/TREATMENT

The treatment of nasolacrimal duct obstruction is, at first, conservative. Peterson and Robb (1978) evaluated the natural history of nasolacrimal duct obstruction, and found that 44/50 (88%) resolved spontaneously using conservative treatment.8 Conservative treatment usually consists of some mixture of nasolacrimal massage, warm compresses, and antibiotics if needed for secondary infection. Crigler in 1922 described massage of the lacrimal sac in an attempt to open the distal nasolacrimal duct by creating an increase in hydrostatic pressure within the sac to break open the distal membrane. This is still the method of choice for nasolacrimal massage.

Surgical intervention consists of the introduction of a flexible metallic probe into the nasolacrimal duct to open it. While classically the obstruction is located at the valve of Hasner, the location of obstruction may be anywhere along the route. A probe is placed into the nasolacrimal duct and passed into the nose (233). The nasolacrimal system can also be irrigated to assess patency following probing. This can be done by using fluorescein-stained balanced salt solution to irrigate with nasal suction to collect the fluid. One must remember, however, that this test does not mimic physiologic tear drainage, and that an open system to irrigation may not stay patent. Various opinions remain as to the most beneficial timing to pursue surgical intervention. Some argue that early intervention will have a higher success rate and allow for probing in the office, eliminating the need for general anesthesia. Others state that the procedure should be delayed as long as possible to allow for maximum spontaneous resolution. Classically, it is thought that the older a patient is at the time of probing, the less successful the probing will be. Katowitz and Welsh (1997) found a decreasing level of success after the first year of life.9 This led to the use of 1 year of age as an ideal time to perform the initial surgical procedure. Various studies show a success rate of 90–95% after initial probing.

Should the initial probe fail, one must decide whether to perform a secondary probing or an ancillary procedure. The two main secondary procedures are balloon dacryoplasty and silicone tube intubation. Balloon dacryoplasty involves the insertion of a balloon catheter on a flexible

233

233 Probing of the nasolacrimal duct. A second metal probe is placed into the nose to confirm passage through the nasolacrimal system.

guidewire into the nasolacrimal duct, and inflation of the catheter to a predetermined pressure for a predetermined time. Success rates for balloon dacryoplasty as a primary procedure have been quoted to be as high as 94%;10 however, the extra cost associated with its usage may preclude its use for common nasolacrimal duct obstructions. It may be useful in recalcitrant cases where other modalities have failed.

Silicone intubation of the nasolacrimal duct can be used as a secondary or primary procedure. Silicone tubes can be bicanalicular or monocanalicular. Bicanalicular silicone tubes consist of the silicone tube with a flexible metal probe on each end. Each separate end is introduced into the upper or lower punctum and then retrieved from the nose. The tube endings are tied in knots to prevent premature removal, and are often secured into the nasal vestibule via a suture. The tubes are kept in for a varying amount of time (surgeon preference), and then removed under general anesthesia. The disadvantages to this system include the possibility of punctate/canalicular tearing secondary to a tight tube and injury to the nasal mucosa while removing the tube from the inferior meatus. The other type of tube is the

monocanalicular stent. This is a single silicone tube with a special footplate at the proximal end to allow for seating in the punctum once located in the duct. The advantage of the monocanalicular stent is that there is no risk of canalicular damage secondary to tight tubing, and the tube may be removed in the office, as it is not secured in the nose. This alleviates the need for a secondary procedure under general anesthesia. There is also much less trauma involved in the insertion of the silicone tube. The nasolacrimal duct is probed in typical fashion using a hollow introducer. A monofilament polypropylene leader is threaded through the introducer into the inferior meatus in the nose. The monofilament polypropylene leader is attached to the silicone tube, and once advanced adequately into the nose, a hook is used to engage the leader and pull it out of the nose. The tube is then pulled into the duct and seated into the punctum. The tube is trimmed and allowed to retract into the nasal cavity. The two main disadvantages to this system include early unplanned removal of the tube and corneal abrasion. In a large study by Engel et al. (2007), 116/685 (16.9%) cases had premature tube removal.11 However, of these patients who had premature tube removal, there was no difference in the recurrence rate compared with those who had the tube removed in the office. There was also a 2% incidence of corneal abrasion. This is believed to be secondary to the footplate rubbing against the cornea. This study looked at primary monocanalicular stent placement for nasolacrimal duct obstruction and found a success rate of 97.3% in patients between 12 and 18 months, and a success rate of 97.5% in patients between 18 and 24 months.11 This suggests that delay of initial treatment could be extended to as late as 24 months if combined with an initial monocanalicular stent placement.

The ideal length of time to leave silicone tubes in place is unknown at the time of writing. Many surgeons leave them in for about 3 months. No study has prospectively looked at the ideal timing of silicone tube removal. The difficulty in comparing any of these secondary procedures is that they intrinsically all contain a nasolacrimal duct probe in addition to their other steps.

Lacrimal sac fistula

ETIOLOGY

Congenital lacrimal sac fistula is a rare entity, occurring in approximately 1 in 2000 births.12 They are often asymptomatic, and only become visualized should the child have concurrent nasolacrimal duct obstruction (leading to tearing through the fistula) or the development of an infection. The fistula is a connection lined with stratified squamous epithelium typically located inferonasal to the medial canthus, usually connecting the skin to the common canaliculus or lacrimal sac.

CLINICAL PRESENTATION AND DIAGNOSIS

The dimple located on the skin is visible, though not always noted if not actively discharging material. Often these patients will have concurrent nasolacrimal duct obstruction, and present with epiphora. Sometimes, the fistula will terminate prior to the nasolacrimal system, and no tears will be present. The fistula can be visualized using fluorescein dye as used to irrigate to check for patency during nasolacrimal duct probing. The fluorescein will be visualized on the skin surface following irrigation.

MANAGEMENT/TREATMENT

The treatment of symptomatic lacrimal sac fistula is surgical. Cauterization of the external opening has been attempted in the past, but does not appear to be successful.13 Complete closure and excision of the fistula are necessary. Silicone tubes may be placed at the same time should distal nasolacrimal duct obstruction be present.

Decreased tear production

ETIOLOGY

While not nearly as common as epiphora, some children experience a lack of tearing. Tear production is broken down into two types: basal tear secretion (produced by the accessory lacrimal glands of Krause and Wolfring) and reflex tear secretion (produced by the main lacrimal gland). Basal tear secretion is nearly always present at birth, whereas reflex tear secretion can occur anywhere from birth to several months of age.2 Often, parents simply notice the lack of tears during crying, and suspect a problem. Children can present with irritation, foreign body sensation, conjunctival injection, photophobia, or corneal scarring.

CLINICAL PRESENTATION AND DIAGNOSIS

Congenital or early-onset lack of tear production will often be the result of a systemic condition such as Riley–Day syndrome (familial dysautonomia)14 and Allgrove syndrome (consisting of alacrima, achalasia, and adrenocorticoid insufficiency).15 Medications can cause a decrease in tear production. Antihistamines, useful in the treatment of allergic rhinitis, are a common cause in the pediatric population secondary to the anticholinergic side-effect, which reduces tear production. Isotretinoin is a common cause in the adolescent population. Examination of the corneal surface is vital when presented with a child with the complaint of absence of tearing. Fluorescein staining can help assess the status of the cornea. Punctate epithelial erosions, frank epithelial defects, and corneal scarring can all be present. The tear lake is diminished. The eyelid margin may have evidence of blepharitis, with lid margin erythema, telangiectasia, or debris. Sjögren’s syndrome, either primary or secondary to other rheumatologic conditions such as systemic lupus erythematosus (SLE), is rare. Absence of the main lacrimal gland is very uncommon.16

MANAGEMENT/TREATMENT

Treatment is aimed at maintaining the integrity of the corneal epithelium. Copious use of tear substitutes, in liquid, gel, or ointment form, allows for adequate protection. Should the use of artificial tears fail, temporary or permanent punctate occlusion may be necessary. Immunomodulatory medication, such as cyclosporine 0.05%, may be useful in extreme cases. Blepharitis, if present, should be treated with warm compresses, lid scrubs, and antibiotics as necessary. Oral antibiotics such as erythromycin or tetracycline may be useful in the treatment of chronic blepharitis. Tetracycline and its derivatives should be avoided in children under age 8 to eliminate the risk of tooth discoloration. Patients with Riley–Day will also have decreased corneal sensation, which can lead to devastating ocular complications. Tarsorrhaphy should be utilized in these cases of decreased tear production associated with poor corneal sensation.