Evaluation and Management of Congenital Nasolacrimal Duct Obstruction





Congenital nasolacrimal duct obstruction (NLDO) is a blockage of the lacrimal drainage system and the most common cause of persistent tearing and ocular discharge in infants and young children. The anatomic site of obstruction is an imperforate membrane at the valve of Hasner located at the distal end of the nasolacrimal duct. The obstruction can be unilateral or bilateral, and signs usually consist of epiphora, discharge, and an increased tear lake. Although most cases resolve spontaneously by age 6 months, several effective treatment options exist for persistent cases. Because of the high rate of resolution, conservative measures are preferred before considering surgical treatment. Recent studies assist the clinician in selection and timing of treatment. Endoscopy has become an important diagnostic and therapeutic tool in patients with anomalous anatomy and surgical failures.


Epidemiology and Risk Factors


Epidemiology


NLDO is diagnosed in up to 6% of newborns, although evidence of impaired lacrimal drainage reportedly exists in up to 20% of infants during the first year of life. Signs of NLDO occur early, with one study reporting 95% of children with NLDO were symptomatic in the first month of life. There is an age-dependent decrease in the rate of spontaneous resolution, with 90% of cases resolving spontaneously by 6 months of age. For cases persisting to 6 to 10 months, about 66% demonstrate resolution. NLDO beyond 1 year is less likely to resolve spontaneously.


Most patients have unilateral NLDO, although about 31% have bilateral disease. Unilateral obstructions appear to resolve slightly earlier than bilateral obstructions. One study found that in infants with NLDO, 38% affected the right eye and 32% affected the left eye. Males and females are equally affected. However, males have symptom resolution slightly earlier than females, which has been hypothesized to be secondary to an anatomically larger nasolacrimal fossa.


Risk Factors


Prematurity may be a risk factor for the development of NLDO, and some degree of blockage has been observed in 16% of premature infants. Bilateral obstruction has been observed in extremely premature children, with the percentage affected inversely correlated with gestational age. Patients with midface anomalies also have higher rates of NLDO. One study found NLDO to be present in almost 22% of patients with Down syndrome. Patients with Down syndrome were found to have distal sites of obstruction, in addition to higher rates of canalicular atresia and stenosis. Children with mandibulofacial dysostosis are also at increased risk of NLDO, and high rates of punctal atresia have been found in this patient population.


Pathophysiology


The nasolacrimal system begins development at gestational day 32. Initially the ectoderm thickens within the nasooptic fissure. This thickened ectoderm resides between the nasal and maxillary processes and eventually becomes more well differentiated. As it extends, an upper branch forms the canaliculi and a lower forms the nasolacrimal duct. Canalization is already occurring in the 60-day embryo. The interface between the distal end of the nasolacrimal duct and the mucus membrane of the inferior meatus, known as the valve of Hasner, is the last point in the ductal system to become patent ( Fig. 11.1 ).




Fig. 11.1


Lacrimal drainage system.


Perhaps not coincidentally, the valve of Hasner is the most common site of obstruction. An assessment of stillborn infants found that 73.3% did not have a patent nasolacrimal passage to the nose. More complicated sites of obstruction include diffuse stenosis of the nasolacrimal duct, intranasal mucoceles/dacryocystoceles, and proximal outflow dysgenesis occurring concurrently with distal obstruction.


Diagnosis


Symptoms of NLDO are often observed within the first weeks of life. The three hallmark signs are epiphora, mucoid discharge, and increased tear lake. Each may present in varying degrees. One study showed that 95% of patients had an increased tear lake, 80% had epiphora, and 68% had mucoid discharge, whereas another study found tearing was the main presenting symptom in 93.4%. Lack of irritation or photophobia is an important consideration when differentiating from other causes of tearing and discharge.


Differential Diagnosis


When a child presents with epiphoria, whether it is due to tear overproduction or outflow obstruction must be explored. Causes of tear overproduction include ocular irritation from causes such as foreign body, corneal abrasion, or infection. Tearing when sucking or chewing may suggest a rare congenital cranial dysinnervation disorder caused by aberrant facial salivary fibers innervating the lacrimal gland.


It is critical that congenital glaucoma be ruled out, as it can present with epiphora. However, glaucoma uniquely is accompanied by blepharospasm and photophobia. Signs include corneal haze/opacification and eye enlargement (buphthalmus). Ruling out congenital glaucoma requires a full ophthalmologic examination, including intraocular pressure measurement, assessment of corneal diameter and haze, inspection of the optic nerve, and cycloplegic refraction.


Although an imperforate valve of Hasner is the most common cause of tear outflow obstruction, other anatomic anomalies present in the same manner. Congenital canalicular atresia is an uncommon cause of NLDO that may be identified during NLDO surgery. Another condition is a lacrimal fistula that may be internal, from nasal mucosa to lacrimal sac or external, connecting the skin to the common canaliculus or lacrimal sac. Lacrimal fistulas have been estimated to occur in 1 in 2000 births. The location is characteristically inferonasal to the medial canthus. Although they are usually asymptomatic, some patients have clear mucoid discharge at the fistula’s ostium.


Another important phenomenon to rule out is a congenital dacryocystocele, which presents around the time of birth as a blue- or pink-colored mass just inferior to the medial canthus. This mass represents a dilated lacrimal sac, which is thought to arise secondary to simultaneous proximal and distal obstruction of the lacrimal system. The proximal obstruction acts as a one-way valve leading to accumulation of mucus, tears, and cellular debris. Secondary infection causing dacryocystitis is common and warrants intravenous antibiotics and procedural intervention. Dacryocystocele with significant nasal extension is an uncommon but important cause of respiratory distress in infants, who are obligate nasal breathers.


Testing


In an infant presenting with epiphora, a fluorescein dye disappearance test can be used to evaluate for obstruction. A drop of fluorescein is instilled in the eye and the tear film is observed after 5 minutes using cobalt blue light ( Fig. 11.2 ). Persistence of significant dye or asymmetric clearance between the eyes suggests an outflow obstruction. One prospective study showed this test to be 90% sensitive and 100% specific in aiding in the diagnosis of NLDO. Contrast dacryocystography and dacryoscintigraphy have been described in the literature as possible diagnostic tools but are rarely performed in clinical practice. Computed tomography and magnetic resonance imaging may have a role in evaluating congenital craniofacial deformities and concomitant nasal or sinus disease.




Fig. 11.2


Increased tear lake and tear overflow of the right eye highlighted using cobalt blue light and fluorescein dye.


Management


Conservative Management


Because of the high rate of spontaneous resolution of NLDO, initial treatment usually involves conservative, nonsurgical measures. For patients older than 1 year who have a lower likelihood of spontaneous resolution, several studies have generated treatment algorithms.


Lacrimal massage has long been advocated as a first-line treatment option for NLDO. Crigler first described his technique for massaging the lacrimal sac in 1923. The technique involved placing one finger over the common canaliculus to prevent upward flow and simultaneously stroking downward along the lacrimal sac with the intent to increase hydrostatic pressure to break the membrane at the valve of Hasner. This particular technique, called the Crigler massage, has been shown to have higher success rates than simple massage or no massage.


Antibiotic drops can be prescribed concurrently with lacrimal massage, although their efficacy has been debated. Investigation into the bacterial flora of the lacrimal system has suggested no difference for patients with and without NLDO. Other studies have suggested trends: Streptococcus pneumoniae was the most common gram-positive and Haemophilus influenza the most common gram-negative bacteria. The organisms in these studies were susceptible to ofloxacin.


Procedural Management


Optimal duration of conservative management has been debated extensively, in part because conflicting reports exist on the rate of spontaneous resolution with age. Some studies seem to suggest high rates of resolution with conservative management even after the age of 1 year. As part of the Pediatric Eye Disease Investigator Group (PEDIG) studies, researchers found that 66% of patients between 6 and less than 10 months had resolution of symptoms with 6 months of conservative treatment alone. These findings were mirrored by another study with a similar age group. If surgery was attempted in patients older than 1 year, some studies did not find an age-related decline in surgical success. However, other reports suggested a delay in surgical treatment led to poorer outcomes.


Because of the differing reports in the literature, there is no consensus on optimal management after 6 months of age. The physician must take into account symptom severity, caregiver concerns, and feasibility of surgery when deciding on further treatment options. Deferring invasive techniques until after 12 months of age spares a portion of patients from procedural intervention. However, there are advantages to escalating care after 6 months of age. In younger patients probing can usually be performed in an office setting with topical anesthetic, whereas older patients need to undergo general anesthesia in a surgical facility. Immediate office-probing ($562) appear to be more cost-effective than observing for 6 months followed by facility-probing ($701) for those children without spontaneous resolution. This, combined with 3 fewer months of symptoms, argues for early probing. However, a very strong argument against early probing is that two of every three infants have spontaneous resolution.


Probing the Nasolacrimal Duct


If conservative management fails, probing is the next possible intervention. The procedure involves dilation of the punctum followed by insertion of a Bowman probe. The probe is gently advanced along the canaliculus while exerting lateral traction on the lid until a “hard stop” at the nasal bone is felt. The probe is then rotated 90 degrees to align with the nasolacrimal duct and is advanced. If a distal membrane at the valve of Hasner is present, a “pop” can be felt as the probe penetrates it. Correct passage into the nasal cavity and patency can be confirmed in several ways: introducing a second Bowman probe in the nostril to allow metal-metal contact of the two probes, injecting fluorescein into the punctum and aspirating from the nose, or endoscopy-assisted visualization ( Fig. 11.3 ).




Fig. 11.3


Endoscopic image of metal Bowman probe exiting the nasolacrimal duct immediately below the inferior meatus.


Endoscopy has become a valuable tool in confirming patency of the nasolacrimal drainage pathway, particularly in cases of abnormal anatomy or dacryocystoceles. Patients with dacryocystoceles have a high likelihood of a nasolacrimal duct cyst at the valve of Hasner, and endoscopy aids in direct visualization and tissue removal. Endoscopic-assisted probing may facilitate improved outcomes in older patients or in those for whom prior probing has failed.


Overall, 80% of patients have resolution of symptoms with a single probing. In a prospective, nonrandomized study, PEDIG found probing successful in 78% of eyes overall, 78% success for patients 6 to 12 months of age, 79% for those 1 to 2 years, 79% for those 2 to 3 years, and 56% for patients 3 to 4 years. This age-related decline has been replicated by other studies, with lower success rates postulated to be secondary to diffuse stenosis in the setting of chronic obstruction.


Balloon Dilation


An alternative to simple probing is balloon catheter dilation, a technique introduced in the 1990s that uses a semi-flexible wire probe with an inflatable balloon tip ( Fig. 11.4 ). Manufacturer protocol advises passing the balloon catheter through the nasolacrimal duct system into the nasal cavity and confirming its position by touching the catheter with a second probe or by direct visualization. The balloon is then inflated for 90 seconds, deflated, inflated again for 60 seconds, deflated, then withdrawn 5 mm, and finally inflated/deflated again for 90 and 60 seconds before withdrawing. Retrospective case series found high success rates with balloon dilation and in the PEDIG prospective study, 82% of patients were successfully treated. Balloon dilation is a reasonable option as a primary procedure, but the higher cost of the procedure compared with simple probing should be considered.


Jan 3, 2021 | Posted by in OPHTHALMOLOGY | Comments Off on Evaluation and Management of Congenital Nasolacrimal Duct Obstruction
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