Pediatric Annals

PEDIATRIC OPHTHALMOLOGY 

Management of Congenital Nasolacrimal Duct Obstruction

Rudolph S Wagner, MD

Abstract

Epiphora or excess tearing in the first year of life has been reported in as many as 20% of children.1 Pediatricians need to be aware of the signs and symptoms of this common disorder. Congenital nasolacrimal duct obstruction or dacryostenosis presents with chronic tearing and eyelid inflammation and, at times, infection that can mimic conjunctivitis. This may be the most frequent ophthalmologic condition during the first year of life.

NORMAL TEAR PRODUCTION

Normal tears provide oxygen and nutrients to the corneal epithelium. They also provide hydration and create a smooth refracting surface. The immunoglobulins and lysozymes in tears serve a bactericidal function.2 There are three components or layers of the precorneal tear film. The inner mucin layer, produced by conjunctival goblet cells, allows aqueous tear fluid to adhere to the hydrophilic epithelium. The accessory lacrimal glands primarily contribute to the middle aqueous layer. The accessory lacrimal glands include the glands of Krause and Wolfring, located at the upper and lower conjunctival fornices. The third layer is the superficial oily layer that slows the evaporation of tears. Meibomian glands, sebaceous glands of Zeis, and apocrine glands of Moll lie along the lid margins and produce this outermost layer.

The main lacrimal gland is responsible for reflex and psychogenic tearing. It is located in a shallow depression within the orbital portion of the frontal bone. The lateral horn of the levator aponeurosis divides the gland into orbital and palpebral lobes. The smaller palpebral portion can often be seen in the superolateral conjunctival fornix when the upper lid is everted. Thinwalled ducts pass down into the superior conjunctival fornix and open approximately 5 mm above the edge of the tarsus, delivering the aqueous tears. A tear lake is formed along the lid margins.3 Reflex tearing begins shortly after birth, but may be delayed for several weeks. Psychogenic tearing (ie, crying) typically begins between 2 and 4 months of age.4

ANATOMY OF THE LACRIMAL SYSTEM

The lacrimal drainage system forms from a depression of ectodermal cells within the nasolacrimal groove. Canalization of this solid cord begins at approximately 3 ½ months' gestation. This process is usually completed at or near the time of birth, with the lower portion of the system being the last to canalize.5-6

Tears enter the drainage system through the upper and lower puncta, which are 0.2 to 0.3 mm in diameter (Fig. 1). The puncta are located on the posterior edges of the lid margins in the lash-free region near the medial canthus. The canaliculus runs medially for approximately 8 mm parallel to the lid margin at a distance of 2 mm. A single common canaliculus enters into the lacrimal sac through its lateral wall. The valve of Rosenmüller, located at the junction of the common canaliculus and the sac, prevents tear reflux back into the canaliculi.

Recently, congenital lacrimal sac mucoceles have been associated with respiratory distress.38 In these cases, an extension of the mucocele from the opening in the inferior meatus interfered with breathing. A blue-gray intranasal mass is visualized using nasal endoscopy or under direct visualization. Imaging studies are helpful in delineating the extent of the mass.39 Obstruction of the respiratory passages requires intervention. Wagner and Lin reported successful management of five cases of lacrimal sac mucoceles.40 They performed probing with nasal endoscopy to visualize the tip of the probe within the cystic mass while producing a perforation from within. The cysts decompressed and were then removed with simple excision. This procedure is curative. Others have reported favorable results using this technique for neonatal dacryocystitis.41

Because nasal extension may occur more frequently than previously realized, nasal endoscopy…

Epiphora or excess tearing in the first year of life has been reported in as many as 20% of children.1 Pediatricians need to be aware of the signs and symptoms of this common disorder. Congenital nasolacrimal duct obstruction or dacryostenosis presents with chronic tearing and eyelid inflammation and, at times, infection that can mimic conjunctivitis. This may be the most frequent ophthalmologic condition during the first year of life.

NORMAL TEAR PRODUCTION

Normal tears provide oxygen and nutrients to the corneal epithelium. They also provide hydration and create a smooth refracting surface. The immunoglobulins and lysozymes in tears serve a bactericidal function.2 There are three components or layers of the precorneal tear film. The inner mucin layer, produced by conjunctival goblet cells, allows aqueous tear fluid to adhere to the hydrophilic epithelium. The accessory lacrimal glands primarily contribute to the middle aqueous layer. The accessory lacrimal glands include the glands of Krause and Wolfring, located at the upper and lower conjunctival fornices. The third layer is the superficial oily layer that slows the evaporation of tears. Meibomian glands, sebaceous glands of Zeis, and apocrine glands of Moll lie along the lid margins and produce this outermost layer.

The main lacrimal gland is responsible for reflex and psychogenic tearing. It is located in a shallow depression within the orbital portion of the frontal bone. The lateral horn of the levator aponeurosis divides the gland into orbital and palpebral lobes. The smaller palpebral portion can often be seen in the superolateral conjunctival fornix when the upper lid is everted. Thinwalled ducts pass down into the superior conjunctival fornix and open approximately 5 mm above the edge of the tarsus, delivering the aqueous tears. A tear lake is formed along the lid margins.3 Reflex tearing begins shortly after birth, but may be delayed for several weeks. Psychogenic tearing (ie, crying) typically begins between 2 and 4 months of age.4

ANATOMY OF THE LACRIMAL SYSTEM

The lacrimal drainage system forms from a depression of ectodermal cells within the nasolacrimal groove. Canalization of this solid cord begins at approximately 3 ½ months' gestation. This process is usually completed at or near the time of birth, with the lower portion of the system being the last to canalize.5-6

Tears enter the drainage system through the upper and lower puncta, which are 0.2 to 0.3 mm in diameter (Fig. 1). The puncta are located on the posterior edges of the lid margins in the lash-free region near the medial canthus. The canaliculus runs medially for approximately 8 mm parallel to the lid margin at a distance of 2 mm. A single common canaliculus enters into the lacrimal sac through its lateral wall. The valve of Rosenmüller, located at the junction of the common canaliculus and the sac, prevents tear reflux back into the canaliculi.

Figure 1. The anatomy of the lacrimal drainage system.

Figure 1. The anatomy of the lacrimal drainage system.

The lacrimal sac lies within the lacrimal fossa, between the anterior and the posterior crura of the medial canthal tendon. The lacrimal sac is 10 to 15 mm in length, with the superior end extending above the canthal tendon.

The nasolacrimal duct is approximately 12 mm in length, and extends from the lacrimal sac through an ostium beneath the inferior nasal turbinate into the lateral portion of the nose. The ostium is partially covered by a mucosal fold called the valve of Hasner, which may remain imperforate.

An active pump mechanism driven by the orbicularis muscles facilitates tear flow. On blinking, the superficial and deep heads of the pretarsal orbicularis contract, compressing the ampullae and shortening the canaliculi. Simultaneous contraction of the deep heads of the preseptal orbicularis, which are attached to the sac, creates negative pressure. This expands the sac and draws in fluid from the canaliculi. When the eye opens, these muscles relax and the sac collapses, forcing tears through the duct into the nose.7

NASOLACRIMAL DUCT OBSTRUCTION

Obstruction, or impatency, of the nasolacrimal duct is the most common disorder of the lacrimal system. In published reports, the incidence of epiphora in infants ranges from 1.2% to 6%.8,9 MacEwen and Young observed a cohort of 4,792 infants in Scotland to determine the incidence and the natural history of nasolacrimal duct obstruction during the first year of life.1 They found evidence of defective lacrimal drainage in 20% of these children at some time during the first year of life.

Dacryostenosis, or atresia, of the nasolacrimal duct is believed to result from failure of canalization of the column of epithelial cells that form the nasolacrimal duct. Adhesions between the ductile epithelium and the nasal mucosa may also be responsible for this condition. Areas of obstruction can occur anywhere along the duct where valves are formed. However, the most common site of obstruction is at the mucosal entrance into the nose (the valve of Hasner), under the inferior turbinate.5

Agenesis of the lacrimal puncta is uncommon.10 This can involve one or more undeveloped puncta, and symptoms will vary depending on which and how many puncta are obstructed. With agenesis or atresia of all four puncta or the two lower puncta, epiphora occurs once the infant begins producing tears. Patients usually present with a watery discharge because there is no reflux of mucus from the blocked puncta.11

Symptoms and Signs

Symptoms of congenital nasolacrimal duct obstruction may be present at birth, but usually appear at a few weeks of age as tear production matures. When the blockage does not resolve spontaneously, symptoms increase during the first few months of life as normal tear production increases. The obstruction may be present in one or both eyes, although it is more frequently unilateral. Ophthalmologists are familiar with the signs of congenital nasolacrimal duct obstruction, which include an overflow of tears onto the lower lid and cheek. This condition is frequently misdiagnosed as chronic conjunctivitis by pediatricians. The absence of conjunctival vascular injection and the presence of lower lid blepharitis suggest congenital nasolacrimal duct obstruction. Reflux from the puncta of mucoid material produced by goblet cells in the lacrimal sac accounts for the parental complaint that the child's lids and lashes "stick together" following sleep. Crusting and mattering of the lashes are usually evident (Figs. 2 and 3). Chronic or recurrent bacterial infectious blepharitis presenting with copious mucopurulent discharge is observed in severe cases. Periorbital cellulitis with localized or diffuse erythema of the adjacent skin and conjunctiva is occasionally found. Conditions that increase nasal congestion such as viral upper respiratory tract infections may exacerbate symptoms of congenital nasolacrimal duct obstruction.

Figure 2. Mild nasolacrimal duct obstruction of the left eye. Note the "wet" appearance of the left eye resulting from an accumulation of tears.

Figure 2. Mild nasolacrimal duct obstruction of the left eye. Note the "wet" appearance of the left eye resulting from an accumulation of tears.

Figure 3. Severe nasolacrimal duct obstruction of the left eye. Note that the lashes are matted together by accumulated mucus, and that conjunctival vascular injection is absent.

Figure 3. Severe nasolacrimal duct obstruction of the left eye. Note that the lashes are matted together by accumulated mucus, and that conjunctival vascular injection is absent.

Figure 4. Bilateral congenital glaucoma with tearing, corneal enlargement, and hazy corneal reflexes secondary to corneal edema.

Figure 4. Bilateral congenital glaucoma with tearing, corneal enlargement, and hazy corneal reflexes secondary to corneal edema.

The clinical diagnosis is usually based on the history and recognition of the signs described in the preceding paragraph. Gentle pressure on the lacrimal sac with the index finger will usually produce a reflux of aqueous or mucoid material through the puncta. The diagnosis can be confirmed with the fluorescein dye disappearance test. A drop of 2% fluorescein solution is placed in the lower conjunctival fornix of each eye. Alternatively, the conjunctiva may be touched with a moistened strip of filter paper impregnated with fluorescein. The excess dye is wiped away from the skin of the lids. The child is then observed from a distance of 3 to 4 feet while the eye is illuminated with a cobalt filtered (blue) light from a penlight, slit lamp, or ophthalmoscope. Normal lacrimal system outflow results in clearance of all dye from the tear lake within 5 minutes. An obvious retention of the dye after 10 minutes is frequent when congenital nasolacrimal duct obstruction is present.

Congenital glaucoma may also present with excessive tearing from one or both eyes. These children will eventually have enlargement of the eye (buphthalmos) and a hazy cornea due to edema, findings not associated with congenital nasolacrimal duct obstruction (Fig. 4).

Natural History

Studies have shown that observation or medical treatment will usually lead to resolution of the symptoms of congenital nasolacrimal duct obstruction. In 1923, Crigler reported nearly 100% success with a conservative regimen that included digital massage of the lacrimal sac.12 Price reported spontaneous resolution of dacryostenosis by 2 years of age in 192 (94.6%) of 203 patients in 1947.13 Peterson and Robb observed the natural history of congenital nasolacrimal duct obstruction in 65 infants and found that 50% were free of symptoms by 4 months of age and 85% by 13 months of age.14 Paul studied 62 patients treated with daily lacrimal massage and topical antibiotic ointment and found resolution by 1 year of age in 90%.15 Nelson et al. showed that symptoms resolved by 14 months of age with a similar regimen in 109 (94.7%) of 113 patients with congenital nasolacrimal duct obstruction.16

Table

TABLEGuidelines for Predicting Spontaneous Resolution of Congenital Nasolacrimal Duct Obstruction

TABLE

Guidelines for Predicting Spontaneous Resolution of Congenital Nasolacrimal Duct Obstruction

In their definitive prospective, MacEwen and Young found an overall rate of spontaneous resolution of 96% at 1 year of age in their cohort of 964 patients.1 It is interesting that they did not prescribe topical antibiotics or lacrimal massage for their patients. Parents were advised to wipe the sticky lids and lashes with cooled boiled water. It is generally accepted that spontaneous resolution is unlikely after 12 to 14 months of age and that surgical treatment is indicated.

Management

Most pediatric ophthalmologists agree that conservative management should be undertaken in the first few months of life, initially by pediatricians. Management includes frequent cleansing of the lids and lashes and application of topical antibiotic drops or ointment when there is a mucopurulent discharge. Digital hydrostatic massage as originally described by Crigler may also be useful.12 This technique involves placing a finger over the lacrimal sac and common canaliculus to block the exit of fluid toward the eye while firmly stroking downward to increase hydrostatic pressure within the lacrimal sac. The induced pressure may rupture a membranous obstruction of the nasolacrimal duct.

Kushner compared treatment with Crigler's hydrostatic massage, simple massage (gentle pressure over the nasolacrimal system to express fluid from the puncta), and no massage in 132 children with 175 affected eyes.17 In this study, 18 of 59 eyes treated with hydrostatic massage improved, compared with 5 of 58 in the simple massage group and 4 of 58 in the control group. However, MacEwen and Young found a 96% resolution rate at 1 year of age, although lacrimal sac massage was never prescribed.1 Although not established as curative, lacrimal sac massage is useful in clearing the lacrimal sac of accumulating mucoid material even if the obstruction is not overcome. Copious amounts of material may reflux from the puncta with gentle massage and can be easily wiped away by parents.

I demonstrate to parents the correct methods of both hydrostatic and gentle massage and advise them to perform this throughout the day as mucoid discharge accumulates. I usually prescribe an ophthalmic antibiotic ointment such as erythromycin or bacitracin to be applied when there is excessive discharge. I also advise frequent cleansing of the lids and lashes with warm water.

Systemic antibiotics have limited usefulness and should be reserved for congenital nasolacrimal duct obstruction with preseptal cellulitis. Parents are advised about the likelihood of spontaneous resolution of epiphora according to the data of MacEwen and Young (Table).1 Children should be referred to a pediatric ophthalmologist by their first birthday if epiphora persists, or sooner if the diagnosis is unclear or they have recurrent episodes of dacryocystitis.

Timing of Probing

There is no universal agreement regarding the timing of the initial probing for congenital nasolacrimal duct obstruction. Despite the natural history of congenital nasolacrimal duct obstruction, with symptoms in more than 90% of children resolving by 1 year of age, some ophthalmologists continue to advocate early surgical probing.18,19 These ophthalmologists suggest that prolonged epiphora annoys both the parents and the child. They also voice concern that a delay in probing may increase the risk of infections and associated scarring of the system, and may decrease the success of initial probing at a later date. Fooks warned that abscess formation in the lacrimal sac may be a consequence of postponing surgical treatment.20 Severe infections such as dacryocystitis are uncommon in children with congenital nasolacrimal duct obstruction and are usually managed successfully with systemic antibiotics. However, probing may be necessary for definitive management.

In a retrospective study of 427 patients with congenital nasolacrimal duct obstruction involving 572 eyes, Katowitz and Welsh reported a 97% success rate when probing was performed before 13 months of age.9 After 13 months, however, the success rate decreased with age (ie, 76.4% for patients between 13 and 18 months old and 33.3% for patients older than 24 months). In contrast, when el-Mansoury et al. reviewed the results of 138 initial probings performed in children between 13 months and 7 years of age, they found that more than 90% were successful regardless of age.21 Robb reported similar data, reflecting a uniform success rate of nearly 90% with first-time probing in children from 1 to 9 years old.22 Recently, Kushner reported that simple probing has an excellent success rate in children up to 4 years old if an uncomplicated obstruction is found at the valve of Hasner.23

Others argue that early probing (in children younger than 8 months) can be performed by the experienced ophthalmologist in the office with the child alert and minimally restrained. This avoids the risks of general anesthesia and eliminates the costs of hospitalization. However, Kushner points out that the current risk of general anesthesia may be exaggerated and not as significant as in the past because of improved administration and monitoring.24 In addition, any cost savings are negated if one considers that 70% (or more) of early probings may not have been necessary because the cases would have resolved spontaneously with time.

In his own series, Kushner probed 175 nasolacrimal duct obstructions in the office before the children were 8 months old.17 He reported a success rate of 97%. In a recent editorial, however, he advised his fellows not to perform office-based probings until they have substantial experience with probing in the more controlled setting afforded by general anesthesia.24

Kassoff . and Meyer have reported success rates of more than 99% for both early office probing and later hospital probing.25 They found few complications with both approaches, implying that either method can be successful. I strongly agree with Kushner, who believes that the complication rate of probings performed in the office when children are 6 months old would be substantially greater if all probings were performed in this way. Many proponents of early probing still select some patients who should be probed in the operating room. To avoid complications such as lacerating the puncta or canaliculus or creating a false passage with a misdirected probe, I suggest that probing be performed under general anesthesia unless the surgeon has experience probing in the office.

SURGICAL MANAGEMENT

Probing and Irrigation

Probing of the nasolacrimal system is performed under general anesthesia, ideally in patients 12 to 15 months old. The procedure may be performed at a younger age if symptoms warrant earlier intervention. A nasal airway or laryngeal mask may be used, or endotracheal intubation may be performed to administer general anesthesia. Preoperative evaluation determines whether the puncta are present and in the normal location.

The upper punctum is dilated using a punctum dilator. A 0 or 00 Bowman probe is passed vertically through the puncta for a short distance and then directed horizontally and medially. The tip of the probe will encounter the medial wall of the lacrimal sac against the lacrimal bone. The probe is then rotated vertically, flat against the face.26 Resistance is often met at the lower end of the duct, and is usually overcome with gentle but steady advancement of the probe. Patency may be confirmed by irrigating fluorescein dye-saline solution through the system and recovering the dye with a suction catheter in the nose. Some surgeons repeat the probing procedure through the lower punctum.

Figure 5. A Crawford silicone tube in place.

Figure 5. A Crawford silicone tube in place.

Failure of the initial probing may require a second procedure in which the probing is repeated. Nasal examination may be performed with inspection of the inferior turbinate.27 If this structure is found to be in tight approximation against the lateral wall of the nose, it may be contributing to the obstruction. In such cases, the turbinate may be fractured toward the septum, using the blunt end of a Freer elevator, a straight hemostat, or a large probe.

Balloon Catheter Dilatation

Balloon catheter dilatation is an effective primary procedure for the treatment of congenital nasolacrimal duct obstruction in children older than 12 months and is also useful after failure of lacrimal duct probing or silicone tube intubation.28 In this procedure, probing is performed as described earlier. A lacrimal catheter is inserted through the puncta and directed into the nasolacrimal duct. Here it is inflated for 90 seconds and then deflated and removed, according to the recommended protocol. This procedure can be highly effective and is particularly useful in older children. Silicone tube intubation can be avoided in many cases.29

Silicone Tube Intubation

When a probing procedure fails, particularly if it was a repeated attempt, silicone tube intubation of the nasolacrimal system should be performed under general anesthesia (Fig. 5). The method developed by Crawford employs a length of silicone tubing fused to the ends of two stainless steel wires.30 The wires are flexible and have a knob or bulb at the tip of the free ends. One wire is passed through the upper punctum, and the other is passed through the lower punctum. Both wires are directed into the nose just as in a primary probing procedure. The bulb ends of the wires are retrieved in the lateral floor of the nasal cavity with a special probe that has a hook on the end. Both wires are brought out through the external nares. The wires are cut from the silicone and the tubes are attached to each other. The tubes can be tied together with multiple knots and allowed to retract into the nose. Some surgeons prefer to secure the tubes by passing the probes through a retinal sponge and securing them with a suture. The sponge is placed below the inferior meatus and can be easily located for removal in the future.31

Regardless of the method that is used to secure the tube, care must be taken to adjust the tension of the loop in the medial canthal area. The loop must be tight enough to prevent corneal touch, yet loose enough so as not to slit the canaliculi. Most surgeons prefer to keep the tube in place for 6 to 12 months, although resolution of epiphora has been reported to occur after 6 weeks.31"33

Children whose symptoms do not resolve following silicone tube intubation may occasionally require dacryocystorhinostomy. This procedure is considered to be less successful in children than in adults because of children's facial bone growth and tendencies toward excessive scar tissue. Nevertheless, Nowinski et al. reported an overall success rate of 83% for dacryocystorhinostomy performed in patients younger than 17 years, and an 88% success rate in cases of congenital nasolacrimal duct obstruction.34

LACRIMAL SAC MUCOCELE

A congenital lacrimal sac mucocele, or amniocele, presents as a blue, firm mass below the medial canthal tendon in the neonate. The mass displaces the medial lower lid superiorly and may occur unilaterally or bilaterally (Figs. 6 and 7). This condition occurs when there are obstructions both proximal and distal to the lacrimal sac. There may be an unusually competent valve of Rosenmüller located at the point where the canaliculi enter the lacrimal sac. Secretions produced by the mucosa lining the sac accumulate and produce this distended hard mass. This mass may resolve spontaneously or with firm massage, warm compresses, and topical antibiotics.35 The sac may refill, however, if relative obstruction remains. Lacrimal sac mucoceles rarely become infected and occasionally produce significant corneal astigmatism.36 Acute dacryocystitis occurs when a mucocele becomes infected. Systemic antibiotics are then required to prevent orbital cellulitis. Pollard recommends immediate probing on diagnosing acute dacryocystitis in neonates.37 In noninfected cases, and if the child is asymptomatic, probing should be performed after a 1- to 2- week period of observation.

Figure 6. A congenital lacrimal sac mucocele with a distended mass displacing the medial right lower lid superiorly.

Figure 6. A congenital lacrimal sac mucocele with a distended mass displacing the medial right lower lid superiorly.

Figure 7. Bilateral congenital mucoceles, displacing the lower lids medially and superiorly.

Figure 7. Bilateral congenital mucoceles, displacing the lower lids medially and superiorly.

Recently, congenital lacrimal sac mucoceles have been associated with respiratory distress.38 In these cases, an extension of the mucocele from the opening in the inferior meatus interfered with breathing. A blue-gray intranasal mass is visualized using nasal endoscopy or under direct visualization. Imaging studies are helpful in delineating the extent of the mass.39 Obstruction of the respiratory passages requires intervention. Wagner and Lin reported successful management of five cases of lacrimal sac mucoceles.40 They performed probing with nasal endoscopy to visualize the tip of the probe within the cystic mass while producing a perforation from within. The cysts decompressed and were then removed with simple excision. This procedure is curative. Others have reported favorable results using this technique for neonatal dacryocystitis.41

Because nasal extension may occur more frequently than previously realized, nasal endoscopy should be included when a probing procedure is performed to treat a congenital lacrimal sac mucocele.

CONCLUSION

Congenital nasolacrimal duct obstruction resolves spontaneously in most cases by the age of 13 months. Conservative management includes massage of the lacrimal sac and application of a topical antibiotic solution or ointment. Probing and irrigation performed under general anesthesia between the ages of 12 and 15 months provide a cure in most persistent cases. Newborns with lacrimal sac mucoceles may experience respiratory distress from nasal extension of the mucocele. These infants should be treated with probing in conjunction with nasal endoscopy.

REFERENCES

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19. Koke MP. Treatment of occluded nasolacrimal ducts in infants. Arch Ophthalmol. 1950;43:750.

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21. el-Mansoury J, Calhoun JH, Nelson LB, Harley RD. Results of late probing for congenital nasolacrimal duct obstruction. Ophthalmology. 1986;93:1052-1054.

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24. Kushner BJ. Early office-based vs late hospital-based nasolacrimal duct probing. Arch Ophthalmol. 1995;113: 1103-1104.

25. Kassoff J, Meyer DR. Early office-based vs late hospitalbased nasolacrimal duct probing: a clinical decision analysis. Arch Ophthalmol. 1995;113:1168-1171.

26. Crawford JS. Surgery of the lacrimal system in. children. Ophthalmology Annual. 1988;4:39.

27. Wesley RE. Inferior turbinate fracture in the treatment of congenital nasolacrimal duct obstruction and congenital nasolacrimal duct anomaly. Ophthalmic Surg. 1985;16:368371.

28. Becker BB, Berry FD, Koller H. Balloon catheter dilatation for treatment of congenital nasolacrimal duct obstruction. Am J Ophthalmol. 1996;121:304-309.

29. Hutcheson KA, Drack AV, Lambert SR. Balloon dilatation for treatment of resistant nasolacrimal duct obstruction. / AAPOS. 1997;1:241-244.

30. Crawford JS. Intubation of the lacrimal system. Ophthal Plast Reconstr Surg. 1989;5:261-265.

31. Leone CR Jr, Van Gemert JV. The success rate of silicon intubation in congenital lacrimal obstruction. Ophthalmic Surg. 1990;21:90-92.

32. Piest KL, Katowitz JA. Treatment of congenital nasolacrimal duct obstruction. Ophthalmology Clinics of North America. 1991;3:201.

33. Migliori ME, Putterman AM. Silicone intubation for the treatment of congenital lacrimal duct obstruction: successful results removing the tubes after six weeks. Ophthalmology. 1988;95:792-795.

34. Nowinski TS, Flanagan JC, Mauriello J. Pediatric dacryocystorhinostomy. Arch Ophthalmol. 1985;103:1226-1228.

35. Levy NS. Conservative management of congenital amniotocele of the lacrimal sac. / Pediatr Ophthalmol Strabismus. 1979;16:254.

36. Bogan S, Simon JW, Krohel GB, Nelson LB. Astigmatism associated with adnexal masses in infancy. Arch Ophthalmol. 1987;105:1368-1370.

37. Pollard ZF. Treatment of acute dacryocystitis in neonates. J Pediatr Ophthalmol Strabismus. 1991;28:341-343.

38. Edmond JC, Keech RV. Congenital nasolacrimal sac mucocele associated with respiratory distress. J Pediatr Ophthalmol Strabismus. 1991;28:287-289.

39. Grin TR, Mertz JS, Stass-Isern M. Congenital nasolacrimal duct cysts in dacryocystocele. Ophthalmology. 1991;98: 1238-1242.

40. Wagner RS, Lin S. Congenital nasolacrimal duct mucocele associated with respiratory distress. Invest Ophthalmol Vis Sd. 1994;35:1445.

41. Lueder GT. Neonatal dacryocystitis associated with nasolacrimal duct cysts. J Pediatr Ophthalmol Strabismus. V 1995;32:102-106.

TABLE

Guidelines for Predicting Spontaneous Resolution of Congenital Nasolacrimal Duct Obstruction

10.3928/0090-4481-20010801-10

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