9.1
Introduction
9.1.1
Anatomy and physiology of the lacrimal drainage apparatus
The lacrimal drainage apparatus is a system that carries tears, produced by the lacrimal gland, from the ocular surface to the nasal cavity. It is defined by the following structures: the puncta, the canaliculi, the lacrimal sac, and the nasolacrimal duct. Moreover, two one-way valves are physiologically important to prevent tear reflux: the valve of Rosenmüller and the valve of Hasner ( Fig. 9.1 ). Different mechanisms have been proposed to describe tear flow from the ocular surface to the nasal cavity, and the most relevant was theorized in 1960s and named “Jones’ pump,” from the name of the ophthalmologist who conceived it.
As for the external oculo-lacrimal anatomy, full knowledge of the endonasal anatomy is fundamental. In particular, the lateral nasal wall in its most anterior part is the area of interest for lacrimal surgery. When introducing the endoscope into the nose beyond the nasal vestibule, the inferior and the middle turbinates are found laterally, inserting onto the lateral wall. In the inferior meatus localized below the inferior turbinate, we find the entrance to the nasolacrimal canal and the valve of Hasner. The middle meatus is below and lateral to the middle turbinate. The most important structures in this region are the uncinate process, the infundibulum with the hiatus semilunaris, and the ethmoidal bulla. In front of the superior insertion of the middle turbinate is the agger nasi, which represents the most anterior ethmoidal cell. Once these structures are recognized, the area that corresponds to the fossa where the lacrimal sac is located should be identified above the insertion of the anterior end of the middle turbinate. In particular, the major portion of the sac (approximately 10 mm) is found above the axilla of the middle turbinate.
9.1.2
Pathology
Disorders of the lacrimal drainage apparatus arise from abnormalities affecting any point along the tears passageway. Canalicular obstruction may be attributed to several etiologies, either congenital , (e.g., punctal atresia, canalicular obstruction, common canalicular stenosis, in cases of anophthalmia or microphthalmia) or acquired. The latter ones may be inflammatory (e.g., blepharitis), traumatic (e.g., canalicular laceration or chemical burn), drug-induced (e.g., by taxanes or Mitomycin), iatrogenic (e.g., prior punctal plugs, punctal cauterization, postsurgical damage, longstanding lacrimal intubation, radiotherapy), or due to local malignancy. However, most cases of lacrimal disorders are ascribable to abnormalities involving the nasolacrimal duct. Nasolacrimal duct obstructions (NLDO) may be classified as either congenital (CNLDO) or acquired. CNLDO is a common disorder in the pediatric population with a prevalence between 5% and 20% in early childhood, causing impaired drainage of tears through the lacrimal system and clinically presenting with epiphora. The acquired NLDO may be idiopathic (or primary), iatrogenic, or posttraumatic. The primary form is the most common, and its etiology is unknown. However, it is postulated that the primum movens for the occlusion of the lacrimal system is inflammation, even of unknown cause, that results in occlusive fibrosis and consequent epiphora.
Possible additional findings in adults are lacrimal sac mucocele or dacryocele/dacryocystocele ( Fig. 9.2 ). They refer to a dilated lacrimal sac that develops secondarily to the coexistence of a distal NLDO, and a proximal functional or structural obstruction (at the junction of the common canaliculus and lacrimal sac). It commonly presents as a mass in the medial canthal region accompanied by epiphora, and sometimes complicated by episodes of inflammation/infection (dacryocystitis/mucopyocele) ( Fig. 9.3 ). Various hypotheses to describe its pathophysiology have been postulated, with two of them being the most accredited ones. A congenital or acquired (due to inflammation or trauma) obstruction of the distal NLD may cause secretions to accumulate within the sac. The increasing pressure on the sac walls may reach the area of junction between the sac and the two canaliculi, causing them to fold upon themselves and displace, resulting in proximal obstruction. The other postulated mechanism includes kinking of the common canaliculus due to malfunction of the Valve of Rosenmüller, that is the entrance of the common canaliculus into the lacrimal sac, secondary to edema and inflammation. Lacrimal sac mucoceles are known to cause bony erosion and remodeling, probably because of both inflammatory mediators and the pressure effect of the mass on the surrounding walls. Occasionally, this process extends to the overlying skin and spontaneous rupture or fistula formation may occur.
For what concerns treatments of pediatric CNLDO, conservative therapy (e.g., observation, lacrimal sac massage, and antibiotics) seem to be the best option in infants aged less than 1 year. On the other hand, in children older than 1 year, probing is successful for most obstructions, even if the timing for probing remains controversial and debated. In adult patients, surgery (e.g., dacryocystorhinostomy) is the gold standard treatment for acquired NLDO.
9.2
Operative techniques
9.2.1
Indications and contraindications
Indications to perform lacrimal surgery include cases of clinically significant epiphora or chronic conjunctivitis in the presence of nasolacrimal duct obstruction, recurrent dacryocystitis, or the presence of dacryoliths in the lacrimal sac that cause recurring episodes of nasolacrimal duct obstruction.
Malignancy of the lacrimal sac represents the only absolute contraindication to lacrimal surgery. Active dacryocystitis is a relative contraindication to the ab externo approach (see Section 9.2.2 ).
9.2.2
Different surgical approaches
Nowadays, different approaches are applied to manage conditions of the lacrimal drainage system. In particular, we find probing of the lacrimal way, balloon dacryoplasty, and ab externo dacryocystorhinostomy (DCR) as surgical alternatives to endoscopic DCR.
9.2.2.1
Probing and irrigation
Probing of the lacrimal way and irrigation is typically insufficient to resolve obstruction in adults, but it may be effective in pediatric cases of NLDO that do not resolve spontaneously or have an incomplete resolution after medical conservative therapy. In cases of recurrent NLDO in which probing was not successful, balloon dacryoplasty or DCR may need to be performed.
9.2.2.2
Balloon dacryoplasty
Some authors consider performing balloon dacryoplasty for adult patients with incomplete obstruction (≤50%), with a success rate varying from 20% to 90%. The procedure consists of dilating the puncta and inserting a Bowman probe. Then, a 3-mm balloon catheter is introduced into the nasolacrimal canal. Once a specific length mark is encountered, the balloon is inflated to a certain pressure and for a certain amount of time. The same inflation is made at precise points as the catheter is progressively retracted.
9.2.2.3
Ab externo DCR
Ab externo DCR is another approach to create a new passageway for tears into the nose. Surgery can be performed under general anesthesia or local-regional anesthesia with sedation (supratrochlear and infraorbital regional blocks may also be used). A vertical incision of approximately 10 mm is made anteriorly to the medial canthus. Then, dissection is carried out till the periosteum and the superficial head of the medial canthal tendon are reached and elevated. The lacrimal sac is encountered, and the fossa is exposed to find the line of the maxillolacrimal bone junction. This is the site of weakness where the bony ostium is created, either by expressing with the periosteal elevator to fracture the bone inward or by using chisel and mallet. The osteotomy is then enlarged up to approximately 10–15 mm in size. Afterward, the lacrimal sac posteromedial wall is tented with a Bowman probe, and it is incised and partially removed. y Nasal mucosa flaps are fashioned and sutured with the anterior sac wall to create the final rhinostomy. The skin is then closed with an interrupted suture, and silicon stents are positioned.
9.2.2.4
Endoscopic DCR
9.2.2.4.1
Evolution of the technique over the years
Endoscopic DCR operation has more than a century-long history. In 1893, Caldwell first described its endonasal approach, while a few years later Toti (1904) published the abovementioned external approach. The latter was initially adopted by the most, as the intranasal anatomy was dominated with difficulties and only poor instrumentation was available. Afterward, the technique varied a lot with the introduction of flaps during the 1920s and lacrimal stenting in the 1960s. During the last decades, the microscope that some authors used was progressively replaced by the endoscope, which was meanwhile grabbing the scene in nasal surgery. At that time, McDonogh and Meiring (1989) described the first modern endonasal DCR. Moreover, the application of argon laser for osteotomies increased over the 1990s. The external way had overall higher success rates (above 90%) and was indeed the preferred one. The application of the endonasal approach increased after endoscopes were introduced, and surgeons became more and more accustomed to them. Nowadays, endoscopic DCR is the standard approach recommended in the ENT field. It established its significance as a comparable technique to external DCR over the years, in terms of controlling lacrimal sac infections (dacryocystitis) and epiphora, with an average success rate of 87%. Compared to the ab externo approach, endonasal DCR has multiple advantages: it avoids the risk of unacceptable cutaneous scarring; it has lower infection rates; it has the potential of prompt intervention in cases of mucopyocele. Some studies showed its additional and superior results to external DCR in the control of epiphora because of sparing Jones lacrimal pump, the periorbital muscular tissue, the skin, and surrounding structures. Moreover, a tailored access to the lateral nasal wall can be adopted in endoscopic DCR, allowing greater precision and bone preservation of the lateral wall anatomy, or concomitant correction of nasal bone variants if sinonasal pathology is present.
Over time, techniques in endonasal endoscopic DCR have changed. However, which one is the most effective is still debated. Novel approaches include the following: the use of nasal mucosal flaps after wide resection of bone; the direct milling of the lacrimal bone without the preparation of flaps; the use of lasers, drills, and/or scalpels. On the other hand, whether an anterior or a posterior approach to the lacrimal sac should be preferred is still a very active matter of debate.
9.2.2.4.2
Description of the technique
In endoscopic DCR, lacrimal structures are approached from the inside of the nose, using endoscopes and sinonasal surgical instruments. The surgical technique that is mostly utilized worldwide is based on the one described by Wormald. However, we have performed some modifications of the standard procedure in our experience. In fact, we do not perform the osteotomy of the frontal process of the maxilla or the preparation of nasal mucosal flaps. The purpose is always a wide marsupialization of the lacrimal sac onto the lateral nasal wall. The endoscope initially used is a camera with a 4-mm 0 degrees rigid optic. The surgical procedure starts with positioning nasal cottonoids with decongestant drugs in the middle meatus of the affected nostril. The first surgical step is retrograde uncinectomy with backbite forceps to show the natural ostium of the maxillary sinus. The vertical portion of the uncinate process is removed to give access to the lacrimal bone, and the cranial opening of a pneumatized agger nasi cell allows a clearer surgical field. The ophthalmologist introduces a light probe through the inferior lacrimal canaliculus, projecting onto the lateral nasal wall. The point of greatest luminescence corresponds to the least thick bone, that is the lacrimal bone. The area is drilled till the lacrimal sac is exposed with a high-speed diamond burr. According to this technique, the preparation of mucosal flaps is not necessary as the sac is exposed posteriorly to the frontal process of maxilla. The residual bone fragments are gently removed with pediatric Blakesley-Weil forceps. At this point, a rigid 4-mm 45 degrees endoscope is used. The lacrimal sac is tented and medialized by the ophthalmologist, producing a gentle pressure on the medial sac wall with the lacrimal probe. The sac is incised and its walls marsupialized with an angled scalpel and a circular cutting punch to expose the sac posterior aspect. The stoma must be as wide as possible to prevent its physiological partial retraction, and it is equally important to limit the exposure of bone surrounding the stoma to avoid excessive scarring. The lacrimal passageway is repeatedly washed with saline solution, then O’Donoghue lacrimal tubes are placed via the canaliculi and tied inside the nasal fossa. At the end of the procedure, one small cotton pattie is placed in the middle meatus for hemostatic purposes and removed at the patient’s dismissal, which occurs 4 h after awakening from general anesthesia in a day-hospital setting. The entire surgery usually lasts about 20 min and has a comparable success rate to the ab externo technique (85%–90%), if performed on one side by an experienced surgeon and without the need of accessory sinonasal functional surgery).
Despite showing lower results in terms of outcomes (success rate of 77%), some surgeons have been recently employing a semiconductor diode laser in endoscopic DCR to create the rhinostomy. This method is certainly faster, but it shows worse results than nonlaser endoscopic or external DCR at this time. Laser-assisted procedures very likely induce fibroblastic activity, thus excessive scarring and stenosis of the rhinostomy compared to the other techniques.
9.3
Exoscope-assisted lacrimal surgery
9.3.1
Introducing the exoscope into lacrimal surgery: considerations
Since January 2019, we have introduced the exoscope (VITOM 2D/3D by Karl Storz, Tuttlingen, Germany) in our operating room when performing lacrimal surgery. It is a compact video microscope with 4K-resolution view and 3D technology, kept upon the surgical field by a specific holder (VERSACRANE), while displaying images on a screen. Provided with digital zooming, it can enlarge images up to 8–30 times, when held at a 20–50 cm distance over the surgical field. Moreover, thanks to exoscope’s integrated control unit, recordings of procedures can be taken with very high quality (see also Chapter 1 ).
In our experience, proficient rhinologic surgeons performed more than 580 procedures (F = 78%, age range 17–84) over a period of 15 years, always in collaboration with ophthalmologists experienced in the field of lacrimal disorders. The exoscope has been introduced into lacrimal surgery with success during the last 18 months. More than 40 procedures were performed by the same experienced surgeons at this time, and an overall approval of this new instrument was obtained. Despite much debate around the best technique to perform DCR, according to the authors, greater interest should be given in enhancing the collaboration between the ophthalmologist and the otolaryngologist, both in the operating room and during the entire diagnostic-therapeutic management of patients with lacrimal system pathology.
The exoscope was initially adapted in the field of lacrimal surgery thanks to its power of image magnification. In particular, a demanding step performed by the ophthalmologist is the correct intubation of the lacrimal way during the procedure: the surgeon—who is not wearing magnifying loops—may need to move close to the patient’s eye for an easier viewing of the lacrimal punctae to perform intubation. This requires great visual efforts and sometimes longer time, if dealing with very small structures, especially in scarcely lit fields. Moreover, the operating room is usually dark during endoscopic procedures, and scialytic lights are used to a minimum. A possible remedy would use the endoscope as a source of light and magnification of the ocular area. However, this often does not prove to be satisfying, and it illogically binds the endoscope out of the nasal cavity. In this setting, the exoscope increases lightning (thanks to the camera light) only over the ocular area. Moreover, it magnifies field dimensions on the screen with excellent quality and without the unnatural rounded-shaping deformation usually caused by endoscopes ( Fig. 9.4 ).
