Dacryocystorhinostomy (DCR) describes the creation of a functional pathway from the canaliculi into the nose by means of creating an osteotomy and opening the nasolacrimal sac into the nose. It can be performed via an external or endonasal approach.
Obstruction of the excretory lacrimal system results in epiphora (tearing). Depending upon the exact cause and location of the obstruction, specific surgical procedures are used. These may include any of the following procedures:
Punctoplasty
Canalicular reconstruction
Canaliculodacryocystorhinostomy
External dacryocystorhinostomy
Endoscopic dacryocystorhinostomy
Conjunctivodacryocystorhinostomy
Dacryocystectomy
This activity will address nasolacrimal duct obstruction (NLDO), which often results in intractable, bothersome epiphora. In longstanding NLDO, mucus can accumulate, resulting in a mucocele in the nasolacrimal sac or even acute or chronic dacryocystitis. Lacrimal surgery to restore tear drainage is usually the definitive treatment and involved one of the types of dacryocystorhinostomy.
History
The 12th-Century Andalusian oculist Muhamad Ibn Aslam Al Ghafiqi described the principles of lacrimal surgery in his book "The Right Guide to Ophthalmology." He reported using a small spear-shaped instrument perforating the lacrimal bone in a nasal direction "until blood flows through the nose and mouth with care given not to direct the instrument downward as this would be the incorrect direction." The probe was then wrapped in cotton that was either "dry or soaked in ox fat." This would then be exchanged every day to maintain the patency of the created fistula. This, then, could be described as the first description of creating an opening from the conjunctival fornix into the nose with secondary granulation and epithelialization, thereby forming a functioning fistula. Considering how little was known of the lining of the lacrimal passages and nose and just as little of the three-dimensional anatomy of the lacrimal system, this was a remarkable procedure. Indeed, this principle of fistulization remains the same to date as that of contemporary conjunctivodacryocystorhinostomy.
The aim of performing a dacryocystorhinostomy is to create a fistula between the nasolacrimal sac and the nose, thus bypassing any obstruction and allowing passage of tears directly into the nose. The currently accepted technique of external-approach dacryocystorhinostomy (DCR) was first described at the beginning of the 20th century by the Florentine professor of otolaryngology, Addeo Toti in 1904 in the Italian literature, and later modified by Dupuy-Dutemps and Bourguet. Toti's procedure exposed the lacrimal sac via an external incision. He then excised the medial wall of the lacrimal sac and removed the adjoining lacrimal and maxillary bone, together with the mucosa: he achieved this with a hammer and chisel. The skin incision was then closed. Pressure was applied externally to push the lateral wall of the lacrimal sac inward, towards the nasal opening. The aim was to create pressure so that the lateral lacrimal sac became the lateral nasal wall with the direct opening of the canaliculi into the nose. The success was hampered by many factors, including the degree of bone and mucosal removal, secondary granulation formation, adhesions, and adequacy of external pressure. Various improvements in the original procedure were made:
Toti modified the procedure in some cases with the removal of a portion of the middle turbinate and made wider bony windows.
Kuhnt in 1914 introduced the suturing of the nasal mucosal flaps to the periosteum to reduce granulation tissue.
Dupuy-Dutemps and Bourget modified Toti's operation in 1921 with vertical incisions in the nasal mucosa and the lacrimal sac together with horizontal incisions at the top and bottom ends of the vertical incisions, thereby creating "book-openings." They sutured both the anterior and posterior flaps of the nasal mucosa and the lacrimal sac. In 1933, they further modified their technique by incising the fistula created and probed the passage repeatedly via the lower punctum to reduce granulation and scar tissue and obtained a success rate of 95% in 1000 cases.
Ohm, in 1962, essentially described a procedure very similar to the one described by Dupuy-Dutemps and Bourget and sutured the nasal mucosa to the lacrimal sac.
Endonasal DCR was first introduced by Caldwell in 1893, who used an endonasal electric burr to removed the bone once a metal probe had been passed through the canaliculus and into the lacrimal sac. Difficulties included adequate visualization, bleeding, accurate bone, and soft tissue removal. Although the technique was later modified by West in 1910 and Halle in 1914, real endonasal surgical improvements came with the rigid nasal endoscopes, which paved the way for advances in the field of endoscopic DCR. The modern-day approach to endonasal dacryocystorhinostomy was first reported by McDonogh and Meiring in 1989. It now being accepted as an effective approach to DCR in the management of epiphora due to nasolacrimal duct obstruction.
While in the 20th century, the most popular approach to DCR was that of an external technique, endonasal DCR, avoiding a skin incision has since been shown to be as successful as the external approach if an appropriate technique is used. It should be emphasized that the term "endonasal" merely describes an approach through the nose rather than a specific technique. It is the evolution and expansion of the many endonasal techniques over time that has led to improved outcomes and greater acceptability and preference for an endonasal approach to DCR surgery.
Endonasal DCR was initially performed using rongeurs and was therefore termed "mechanical" endonasal DCR. With the advent of laser technology and the improvement of rigid nasal endoscopes, endoscopic "laser" DCR was popularised. However, lasers were unable to remove the thick bone of the frontal process of the maxilla and root of the middle turbinate, resulting in smaller bony ostea, extensive scarring, and, ultimately, higher failure rates. This led to a shift to the principles of "powered" endoscopic DCR. These principles mimicked those of external DCR, namely a large bony ostium, usually achieved by powered instrumentation, mucosal flaps, and mucosal edge-to-edge apposition, thereby aiming for primary intention healing and minimizing soft-tissue scarring. In an effort to reduce consumable costs, "powered" endoscopic DCR techniques have since evolved to use newer designed instruments, thus avoiding the need for powered instrumentation and, in effect, a shift back to mechanical endonasal DCR, while achieving full sac exposure and still creating mucosal flaps.
Since the end of the 20th century, there has been a shift towards endoscopic DCR being accepted as being as safe and effective as external DCR. A large bony ostium (similar to that achieved in an external approach) is essential, and the mucosal flaps created intraoperatively should be well apposed for mucosal anastomosis. Endoscopic procedures that remove the adequate bone for full lacrimal sac exposure, marsupialization, and mucosal flap apposition have very high success rates, ranging between 90% to 100%.
A recent study comparing various endoscopic DCR techniques reports equal safety and effectiveness. Endoscopic DCR can also be effectively used in the pediatric population, in patients with craniofacial syndromes and syndromic nasolacrimal duct obstruction and the setting of distal canalicular or common canalicular obstruction. While endoscopic DCRs are on the rise, the majority of DCR surgeries in the U.S.A. remain external.
Anatomy
An appreciation of precise anatomy is essential to understand the process of DCR surgery. The lacrimal drainage pathway includes the lacrimal punctum (plural: puncti or puncta), the canaliculus and nasolacrimal sac, and finally, the nose. (fig 1)
Lacrimal Punctum
The punctum is located on the lacrimal papillae, facing slightly towards the globe, on both the upper and lower lids. This small aperture of approximately 0.3mm diameter allows the flow of tears into the canaliculus and is part of the lacrimal pump by means of a siphoning action.
Canaliculus
The upper and lower eyelids have one canaliculus each. These are lined with nonkeratinized squamous epithelium. The canaliculus initially travels about 2 mm vertically, and then turns horizontally in parallel with the eyelid margin. This horizontal component of the canaliculus is surrounded by Horner's muscle, which is part of the lacrimal part of orbicularis oculi. Horner's muscle contributes to the lacrimal pump function, and any dysfunction of orbicularis oculi may contribute to epiphora due to pump failure. In most individuals (94%), the canaliculus from the upper and lower lid converge and join to form the common canaliculus. The length of the upper canaliculus is about 8mm, whereas the lower canaliculus is about 10 mm.
The upper and lower canaliculi each angle slightly posteriorly, but the common canaliculus, in turn, may angle anteriorly. Awareness of this change in direction is essential for safe, atraumatic syringing and probing, which constitutes part of the assessment and pre-operative workup. The common canaliculus then pierces the periorbita and enters the lacrimal sac. However, in some individuals, separate upper and lower canaliculi may enter the sac. The entry into the lacrimal sac most often occurs obliquely, which forms the valve of Rosenmueller. While this is not a valve per se, the angulation of the common canaliculus as it enters the sac prevents retrograde flux and acts in a valve-like manner.
Lacrimal Sac and Duct
The nasolacrimal sac and duct are continuous rather than separate structures that are lined with non-ciliated columnar epithelium. The sac sits within the lacrimal fossa, which is formed by the lacrimal bone and the frontal process of the maxilla. Its dimensions are 12 to 15 mm in height and 4 to 8 mm anteroposteriorly. The superior fundus of the sac extends 3 to 5 mm above the medial canthal tendon. The nasolacrimal duct extends inferolaterally and posteriorly through the bone for approximately 12 mm, exiting underneath the inferior turbinate. This nasolacrimal duct ostium is located 25 to 30 mm posterior to the anterior nares. The exit of the nasolacrimal duct into the nose is can be round or slit-like and is protected by a mucous membrane covering, called the valve of Hasner or plica lacrimalis.
Endoscopic Nasal Anatomy
Endonasal anatomy is complex: a detailed discussion is beyond the scope of this chapter. However, a few salient points must be highlighted to understand DCR surgery. The review by Shams et al. is an excellent review of applied endonasal anatomy.
The lacrimal fossa is formed by the frontal process of the maxilla anteriorly and the lacrimal bone posteriorly. The fossa is bordered by the anterior lacrimal crest and posterior lacrimal crest. The lacrimal fossa measures about 16 mm vertically is 2 to 4 mm deep with a width of 7 to 10 mm. Variability exists depending upon ethnic origins.
The nose has three turbinates, each of which has a corresponding meatus inferior to it. The nasolacrimal duct opening lies within the inferior meatus, but it is the middle turbinate which may guide the DCR surgeon. The middle meatus contains the uncinate process, the bulla ethmoidalis, the frontal recess, and the maxillary sinus ostium. The axilla of the middle turbinate marks the point of the middle turbinate inserting into the frontal process of the maxilla and tends to be a constant anatomical landmark. The lacrimal fossa is situated superiorly, anteriorly and laterally to the axilla of the middle turbinate.
It is essential to appreciate the extent of the sac with respect to the middle turbinate to perform successful endoscopic DCR. The sac extends 8 to 10 mm above the superior extent of the middle turbinate and about 4 mm below its inferior border. This means that a significant part of the lacrimal sac fundus lies above the axilla of the middle turbinate, and it is essential to adequately expose this during DCR surgery in order to minimize failure.
The maxillary line is the most medial part of the frontal process of the maxilla, and it runs from the axilla of the middle turbinate along the lateral nasal wall ending at the inferior turbinate. It is an important landmark for the placement of mucosal incisions.
The uncinate process attaches to the lateral nasal wall at the frontal process of the maxilla. Inferiorly, it attaches to the ethmoidal process of the inferior turbinate. The infundibulum is an area lateral to the uncinate process, into which the maxillary sinus and anterior ethmoid air cells drain. During the creation of the bony ostium as part of endoscopic DCR surgery, the uncinate process helps define the posterior-inferior extent of bone removal involving the lacrimal bone covering the lacrimal sac. Once the uncinate process is encountered, further ostium creation can extend upwards.
The agger nasi cells are situated in the lateral nasal wall and are pneumatized to varying extents in different individuals. They may displace the insertion of the middle turbinate medially and can be seen well on computerized tomography (CT), anterior to the middle turbinate. They are usually closely situated near the posterior-superior aspect of the lacrimal fossa and may extend superiorly above the lacrimal fossa.
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