Once bone has been breached, bone removal should proceed anteriorly across the anterior lacrimal crest and this can be most readily achieved with a Kerrison-style rongeur, crossing the crest close to the skull base—this being the thinnest bone on the crest and also reducing the chance of damage to the nasal mucosa (Fig. 8.2a); a periosteal elevator should be swept around the bone edge (every two or three bites) to separate the nasal mucosa from underlying bone. Nasal mucosa is reached as the anterior lacrimal crest is crossed and, at this point, it is best to slightly withdraw the epinephrine-moistened cotton buds and they may be readvanced to the apex of the nasal space once the bone removal is complete. Once across the anterior crest, bone removal should be directed inferiorly to the level of the inferior orbital rim—creating an ‘L’-shaped rhinostomy. The remaining bone of the frontal process of the maxilla is removed, either with down-cutting rongeurs or straight (Jensen) bone-nibblers, the lacrimal sac tissues being protected by displacing it laterally with the sucker held in the non-dominant hand. The thin hamular process of the lacrimal bone, between the upper part of the nasolacrimal duct and nasal mucosa, is removed with bone-nibblers and the upper part of the rhinostomy is extended to the skull base, although care should be taken here to avoid shearing forces that may fracture the cribriform plate and cause a cerebrospinal fluid (CSF) leak. At this stage, the rhinostomy should be about 12–18 mm diameter and extend from the fundus of the sac at the skull base, up to 10 mm in front of the anterior lacrimal crest, and inferiorly to expose the upper part of the nasolacrimal duct (Fig. 8.2b). Anterior ethmoidectomy should be performed, using non-toothed forceps or a fine artery clip to palpate and avulse the fragment of bone and mucosa, as this creates a wide-open space that facilitates easy apposition and suture of the posterior mucosal anastomosis.

A ‘00’ Bowman probe is passed into the lacrimal sac through the lower canaliculus, and the assistant maintains gentle medial pressure to “tent” the medial wall of the sac whilst the medial face of the sac is opened with a #11 blade; this blade should be directed away from the internal opening of the common canaliculus (Fig. 8.3a). Once in the sac, the closed blades of a Westcott spring scissor should easily pass into the lumen of the sac and duct (Fig. 8.3b); difficult passage commonly indicates that lacrimal fascia alone has been opened and the blades have entered the resistant sub-mucosal (extraluminal) plane. The entire sac is opened by extension of the blade incision in both directions (Fig. 8.3c)—from the fundus down to the duct and the sac is further opened with relieving incisions at the skull base above and the nasolacrimal duct below (Fig. 8.3d); cautery of the sac–duct junction is advisable before the relieving incisions, as there is a rich vascular plexus at this site.

The internal opening of the common canaliculus should be clearly visible and deliberately inspected (Fig. 8.3d): Where membranous obstruction is present, the adherent Valve of Rosenmuller should be excised by grasping it with a pair of fine, toothed forceps and excising about 1 mm² using a #11 blade. Likewise, biopsy of suspicious lesions within the sac, or removal of any debris (such as stones), is readily accomplished with the sac opened widely.

Using the #11 blade with the cotton buds protecting the nasal septum, the nasal mucosa is opened in a superior–inferior direction and the incision placed 3–4 mm anterior to the “arch” formed by the inflexion of the nasal mucosa into anterior insertion of the middle turbinate; this arch only being evident after anterior ethmoidectomy. The anterior flap is created by superior and inferior positioned relieving incisions (Fig. 8.4a) and the posterior flap similarly created after mucosal cautery. A 6-0 soluble suture (e.g., Vicryl W9756; Ethicon) is passed through the orbicularis muscle on the anterior lip of the incision and then through the middle of the free edge of the anterior nasal flap (Fig. 8.4b), the suture being clipped and draped across nasal bridge—this keeping the anterior flaps out of the surgical field during posterior suturing.

The posterior mucosal flaps are apposed—from the skull base (Fig. 8.5) to the entrance of the nasolacrimal duct—with a locked continuous 6-0 Vicryl suture and the suture secured by a triple locking throw. Silicone tubes are passed through the upper and lower canaliculi, retrieved through the incision using a curved haemostat, the metal bodkins removed, and the tubes tied over the shank of the closed haemostat resting across the incision (Fig. 8.6a). While the assistant holds both tubes elevated, a 2-0 silk ligature is tied just above the silicone knot and the ends left about 15 mm long to facilitate identification within the nose; the tube ends are then passed into the nose and retrieved with a curved haemostat passed from the nasal entrance (Fig. 8.6b).