Schematic diagram showing the outbudding of solid canaliculi from the lacrimal cord (Photo Courtesy: Dr. Himika Gupta)
Schematic diagram showing the process of canalization (Photo Courtesy: Dr. Himika Gupta)
Therefore development of the lacrimal sac and nasolacrimal duct occurs earlier than the canaliculi, but the caudal end of the nasolacrimal duct is the last to canalize . This explains why pathology in CNLDO is mostly present at the distal end, where the NLD normally opens into the inferior meatus (Fig. 12.3).
Cadaver midsagittal head section showing the lateral wall and the probe entry into the inferior meatus
CNLDO: Types and Variations
A number of variations of CNLDO were described way back in 1976 by Jones and Wobig . These variations are seen in the lower end of the NLD, and the most common one described is the duct that fails to open through the nasal mucosa and stops at the vault of the anterior end of the inferior nasal meatus (Fig. 12.4a–f). The other variations include the NLD extending lateral to the nasal mucosa, extending up to the floor, complete absence of the duct or the impacted anterior end of the inferior turbinate, etc. (Fig. 12.4a–f).
Schematic diagram showing various CNLDO variations: nasolacrimal duct (NLD) entering at vault of the inferior meatus (a). NLD extending up to the floor lying lateral to the nasal mucosa or a buried probe (b). NLD obstruction caused by impacted anterior end of the inferior turbinate (c). NLD ending in the anterior end of the inferior turbinate (d). NLD ending blindly into the maxillary wall (e). Complete absence of NLD (f) (blue lacrimal sac and NLD, yellow lateral wall of nose, orange inferior turbinate)
Kushner first described the types of CNLDO into simple and complex based on intraoperative findings during probing . In cases of simple obstruction, there is lack of resistance in passing the probe through the NLD until a point of membranous obstruction can be perforated. Simple obstruction also includes cases of canalicular valves, where resistance is encountered while bypassing them although there may not be true obstruction. Complicated obstruction can be those associated with any of the variations described earlier like a buried probe, a bony obstruction, nondevelopment of nasolacrimal duct, NLD opening into the inferior turbinate, and anlages.
The characteristic triad includes watering, discharge, and matting of eyelashes. In 95 % of cases, the onset of epiphora is within the first month of age . The condition can be unilateral or bilateral. Symptoms may worsen with occurrence of upper respiratory tract infection. Other signs include increased tear meniscus height, positive fluorescein dye disappearance test (FDDT), and regurgitation on pressure over the lacrimal sac (ROPLAS). A spectrum of presentation can rarely include acute dacryocystitis, dacryocele, mucopyocele, and preseptal and orbital cellulitis (Fig. 12.5a–f).
Clinical spectrum of CNLDO: typical manifestation with increased tear meniscus, discharge, and matting of eyelashes (a). Left dacryocele (b). Bilateral CNLDO presenting with right-sided acute dacryocystitis and left-sided mucocele (c). Superadded infection of right-sided dacryocele (d). Infected dacryocele complicating into orbital cellulitis (e). Congenital lacrimal fistula at typical location near the medial canthus (f)
Dacryocystoceles or simply dacryoceles are bluish cystic lacrimal sac swelling typically present below the medial canthal tendon, filled with secretions from epithelial lining and tears (Figs. 12.5b and 12.6). It is an uncommon manifestation of CNLDO occurring in 1 in 3,900 live births . Nasolacrimal duct obstruction when combined with either functional obstruction of the proximal lacrimal system or common canaliculus leads to accumulation of secretions in the lacrimal sac. This leads to distortion of the common canaliculus and creates a ball-valve mechanism at the valve of Rosenmuller which allows ingress of tears into the sac but interferes with egress . Dacryocystocele can be bilateral in 25 % of cases and can complicate into superadded infection and respiratory distress [5, 11]. Associated intranasal cyst (Fig. 12.7) can be small or large (if >50 of the nasal cavity) and, if large, can cause respiratory insufficiency because infants are nasal breathers, which can be life-threatening in cases of bilateral pathology . Infection can lead to preseptal cellulitis, orbital cellulitis, and sepsis, therefore indicating early management of this condition. In the absence of intranasal cysts, dacryocele can be managed conservatively, and success rate achieved with sac compression alone was 76 % in one of the series . In non-resolving cases and associated intranasal cyst, it is preferable to marsupialize the intranasal cyst early. Ali et al.  defined and classified the intranasal cysts as small and large and described a new technique of cruciate marsupialization for large intranasal cysts with good results on long-term follow-up.
Left congenital dacryocele
Endoscopic view of an intranasal cyst
Lacrimal fistula (anlage duct) is seen in 1 in 2,000 births . It can cause epiphora (seen from the fistulous opening), discharge, dermatitis, and ascending infection causing acute or chronic dacryocystitis (Figs. 12.5f and 12.8). There are many theories postulating its formation; the most accepted one is that lacrimal fistula is an aberrant canaliculus which often originates from a common canaliculus or canaliculus and lined by a nonkeratinized stratified squamous epithelium resembling a canaliculus [14, 15]. Other associated lacrimal anomalies include CNLDO, absent canaliculus, supernumerary/absent punctum, and total agenesis of the lacrimal system . A careful fistulectomy is performed when the lacrimal system is patent, but in cases of CNLDO, the authors prefer probing first and to wait for 6 months for a spontaneous closure of the fistula secondary to no flow. However if fistula persists, a fistulectomy can be performed.
Syndromes and Craniofacial Abnormalities Associated with CNLDO
Syndromic associations include Down’s syndrome (trisomy 21), Crouzon syndrome, Treacher Collins syndrome, Klinefelter syndrome, and Rubinstein-Taybi syndrome . Associated craniofacial abnormalities include: cleft lip/palate, facial cleft, hypertelorism, bifid uvula, hemifacial microsomia, preauricular skin appendages, deformed external ears, and laryngeal stenosis (Fig. 12.9) .
Syndromic association with CNLDO
A thorough knowledge and understanding of the natural history of CNLDO is a must for making a decision regarding the management as well as explaining the prognosis to the parents. In the landmark study by MacEwen and Young published in 1991, a large cohort of 1,019 eyes of infants were observed to determine the incidence and natural history of epiphora during the first year of life . In 95 % of cases, the onset of epiphora was within the first month of age and thereafter 3 % in the second month and less than 1 % in the third and fourth months of age. Spontaneous resolution was observed throughout the year from the first month, and by 1 year of age, overall spontaneous resolution rate was 96 %. The authors also provided the probability of spontaneous resolution, i.e., the percentage of infants at each month, who on follow-up, resolved before age 12 months. Table 12.1 reflects the rounded up figures, making it easy to remember. This study provided the evidence that the probing should ideally be delayed until 1 year of age but did not provided the optimum age at which probing should be considered.
Predicting the probability of spontaneous resolution of CNLDO by 1 year of age at various months of presentation  (Numbers rounded for easy memory!)
Spontaneous resolution probability (%)
In subsequent study by the same researchers on CNLDO during the second year of life, it was noted that at 15 months of age, probing is superior to “no treatment” with statistical difference, but at the age of 24 months, there was no statistical difference between the two groups (74 % resolution in the probing group versus 60 % in the observation group) . Spontaneous resolution remains a common occurrence during the second year of life with about 50 % rate (among the residuals) between 13 and 18 months and 23 % between 19 and 24 months of age. Appropriate time of probing recommended was 18 months of age if there are no signs of resolution.
Paediatric Eye Disease Investigator Group (PEDIG) studied the resolution of CNLDO with 6-month observation for infants presenting between 6 and <10 months old . In this age group, more than half of the eyes (~66 %) resolved.
The most common outcome of CNLDO is the spontaneous resolution without the surgical intervention. Topical antibiotics are needed when there is purulent discharge and conjunctivitis or associated acute dacryocystitis. However, some surgeons prefer antibiotics more so for their additional anti-inflammatory actions as well. Various treatment options in CNLDO are conservative with compression over the lacrimal sac area, probing, intubation, balloon catheter dilation, endoscopic-assisted correction of associated nasal abnormalities, and, as a last resort for recalcitrant cases, an endoscopic or external dacryocystorhinostomy (DCR).
Conservative with Compression Over the Lacrimal Sac Area
Hydrostatic pressure over the lacrimal sac area was described by Criggler in 1923. The aim was to increase the intraluminal pressure and direct it downward (by compressing the common canaliculus) to rupture the membrane (Hasner valve) at the lower end of the NLD (Fig. 12.10a, b). The success rate observed in various studies ranged from 30 to 93 %  being the maximum when done early in life and as compared to older age group. Other factors for success include a correct technique of sac compression and compliance. It appears that sac compression essentially causes earlier resolution of CNLDO symptoms when compared to natural history. In clinics, the correct method of sac compression should be demonstrated to the parents or caregivers and encouraged to perform the technique under clinician supervision. Depending upon the treating physician, sac compression can be continued till age of 9–12 months, and if symptoms persist, probing is advised.
(a) Technique of Crigler’s lacrimal sac compression. (b) Closer view of the exact technique
Method of Sac Compression
Parents should be instructed to wash hands and use the index finger for sac compression. Pressure should be directly applied over the lacrimal sac area, just on the inside of the anterior lacrimal crest, below the medial canthal tendon and without compressing the bone or eye. Usual frequency advised is ten times/session with 4 sessions per day (Fig. 12.10a, b).
Probing: Early Office-Based Versus Late Probing Under General Anesthesia
Probing is indicated if symptoms and signs of CNLDO persist despite lacrimal sac compression. Age at which probing is indicated is debated in literature but is usually after 6 months of age . Early probing usually done between 6 and 9 months of age is an office procedure practiced by some which avoids general anesthesia and is done under topical anesthesia and restraint. Late probing after 9–12 months of age is done under general anesthesia and is technically easier. Adopting early office probing would result in probing approximately two-thirds of infants in whom obstruction would spontaneously resolve on follow-up of 6 months . Early probing for 6 to <10 months of age group has a success rate of 92 % compared to 82 % with late probing when done after 6 months of observation .
PEDIG concluded that although CNLDO resolves spontaneously in two-thirds of cases presenting between 6 and <10 months of age group, early office-based probing is effective and cost-saving when compared to late probing with an added advantage of 3 months of fewer symptoms. But the treatment decision rests entirely upon the parents and physician weighing the risk/benefit ratio. The authors of this chapter prefer to avoid office-based probing because it causes undue stress on infants and parents. A more controlled irrigation and probing under general anesthesia also allows a more detailed evaluation of the lacrimal system as well as diagnosing and treating suspected nasal pathology with an aid of an endoscope.