Revision Endoscopic Dacryocystorhinostomy and Conjunctivodacryocystorhinostomy

Inadequate Bony Osteotomy

Many studies have demonstrated primary DCR failure secondary to inadequately or inappropriately placed osteotomies. When performing a DCR, it is vital that the surgeon have a thorough knowledge of the lacrimal anatomy and its relationship to nasal anatomy. Fig. 15.1 demonstrates a patient whose external DCR failed as the result of inappropriate placement of the osteotomy. The lacrimal sac rests in an ovoid fossa measuring approximately 15 × 10 mm along the maxillary line. The frontal process of the maxilla contributes the anterior half of the fossa and the thin lacrimal bone provides the posterior half. In 2000 Wormald, Kew, and Van Hasselt performed a radiographic analysis of cadavers that demonstrated that the lacrimal sac often is located higher on the lateral nasal wall than previously thought. In this study, the location of the lacrimal sac was found to extend to a mean height of 8.8 mm above the middle turbinate insertion and approximately 5.3 mm above the common canaliculus.

When placing the osteotomy, it is important that it is not only in an adequate position but also of sufficient size. One prospective study demonstrated ostium shrinkage of approximately 35%, with the majority of size change occurring in the first 4 weeks postoperatively. After 4 weeks the ostium size does not appear to change significantly. Linberg et al. were the first to endoscopically examine the size the postoperative intranasal ostium after external DCR but did not find correlation between the final and the intraoperative osteotomy size. More recent studies using internal ostium photography have shown a correlation between larger intraoperative osteotomy size and postoperative intranasal neo-ostium size. Although the overall size of the osteotomy may not directly correlate with surgical success, it is believed that osteotomy size must be sufficiently large initially to prevent complete closure with known postoperative contraction. Therefore if the initial bony osteotomy is not large enough to expose the entirety of the lacrimal fossa after the ostium contracture occurred, failure may ensue. The primary objective is adequate exposure of the common internal punctum (canaliculus).

Mucosal Scarring

Mucosal contracture is a common cause of DCR failure. Evaluations of failed primary DCRs, both external and endonasal, have demonstrated that approximately 50% of failures are due to cicatricial scarring of the neo-ostium ( Fig. 15.2 ). After bony osteotomy is created, the entirety of the medial wall of the lacrimal sac should be exposed and then incised sufficiently so that the entirety of the sac is marsupialized and the common canaliculus is exposed. If during this process there is excessive mucosal injury, either to the nasal or lacrimal mucosa, it could contribute to more scarring and increased ostial shrinkage. In addition, inflammation during healing could lead to the formation of granulomas or intranasal synechiae, which can contribute to ostium obstruction ( Fig. 15.3 ). Some groups advocate for apposition of nasal and lacrimal mucosa (preservation of mucosal flaps), encouraging primary wound healing and thus decreasing scar formation. It is our belief that the presence of redundant mucosa may contribute to excess scar formation in certain cases and thus should be trimmed, if present, to allow for optimized healing by secondary intention. We have found this technique of not preserving the mucosal flaps to produce comparable outcomes.

Concomitant Nasal Pathology or Anatomic Variations

It is important for the surgeon performing DCR to recognize the potential implications of intranasal pathology and anatomic variations. Abnormalities, such as a deviated septum, lateralized middle turbinate, or concha bullosa of the middle turbinate, can cause a physical obstruction of the osteotomy. In addition, if those structures have any mucosal injury at the time of primary DCR, synechiae may form, causing additional obstruction. Other nasal pathologies, such as the presence of nasal polyps, may also contribute to neo-ostium obstruction postoperatively and should be addressed at the time of DCR. Although concomitant nasal pathology contributing to anatomic failure is more common after external DCR, it may also serve as a source of failure after endoscopic DCR.

It is also important to note that normal anatomic variations may result in obstruction of the neo-ostium. In their review of 25 revision DCRs, Liang et al. evaluated the anatomic relationship of the agger nasi cell with the lacrimal fossa. They found that, when present, 95% of agger nasi cells overlap the lacrimal fossa. Similarly, Soyka, Treumann, and Schlegel noted that if this relationship is not recognized, then the neo-ostium may be partially or completely obstructed by the agger nasi, thereby causing DCR failure. In other words, failure to adequately open the agger nasi cell may lead to poorer outcomes.

Functional Failure

Despite meticulous surgical technique, studies frequently describe a subset of patients in whom functional failure develops after both external and endoscopic DCR. Functional failure—the persistence of epiphora—despite a patent neo-ostium, is not fully understood. However, it is thought to be secondary to proximal problems with the lacrimal system, such as dysfunctional lacrimal pump mechanism, eyelid laxity, or canalicular stenosis. It is important to recognize proximal dysfunction of the lacrimal system, such as eyelid laxity, before performing DCR to limit functional failure.

Although endoscopic DCR does not disrupt the bony or soft tissues that support that lacrimal system, external DCR requires an external incision through these support systems. Damage to the peripheral fibers of the facial nerve that innervate the medial orbicularis oculi, leading to poor eyelid closure and poor lacrimal pump function, has been demonstrated after external DCR. In the study of 247 external DCRs by Vagefi et al., there was a 7.4% incidence of temporary orbicularis weakness after surgery. Eyelid laxity, punctal position, punctal size, and canalicular tortuosity or stenosis may also contribute to poor tear film drainage and functional obstruction. In addition, Lee et al. examined the endoscopic features associated with functional failure after 50 external DCRs. Their study demonstrated that, despite anatomic success, 16% of patients demonstrated functional failure. Examination of the neo-ostium shape of those with functional failure demonstrated that a neo-ostium that healed in the cavernous shape, described as a large osteotomy with preservation of the lacrimal sac, were more likely to have functional failure. They hypothesized that this remnant sac, which was not incised fully during the primary surgery, obstructed the drainage pathway.