The surgical options for treating failed DCR surgery are well known, with surgeons tailoring their surgery to the approximate anatomical abnormality. In this study, we examined the DCG anatomical abnormality that led to DCR surgery failure, and reported the success rates of subsequent surgeries according to the anatomical abnormality.
Causes of epiphora and stickiness recurrence identified on DCG
The most common DCG finding after failed DCR surgery was that of a well-sized and patent anastomosis with brisk flow of contrast into the nasal space (36%), which was followed by a narrow surgical anastomosis (31%), and completely closed anastomosis (19%). This study showed a similar percentage of DCG failure attributed to ‘inadequate ostium size or location’ (84/160, 53%) as that reported 30 years ago at this institution (111/204, 54%)(5). In that study, Welham et al., also found similar rates of anastomoses into a nasal sinus, reflecting the need for more awareness for this unusual cause of DCR failure. Conversely, we are fortunately now seeing a much lower rate of common canalicular obstruction in our cohort (8%) compared to the past (53%)(5). It is unclear whether this reflects a difference in the incidence of cicatricial canalicular disease(11) or a reduction in inadvertent iatrogenic canalicular trauma during syringing in clinic, or during intubation in DCR surgery. Unfortunately, as a tertiary referral centre, our department does not have documented canalicular assessment prior to primary DCR surgery, which was performed at other institutions.
Success rates of subsequent corrective surgery, according to DCG anatomical abnormality
The results of subsequent surgery are presented in the flowchart, with the authors’ recommended surgical option for each DCG category circled in green (Figure 3). In all but one category, this is the procedure with the highest percentage success rate. In the ‘completely closed anastomosis’ category, despite LJT having 100% success, the authors have recommended redo-DCR surgery in the first instance. This is because only one patient with a narrow surgical anastomosis was treated with LJT. Furthermore, LJT requires life-long maintenance and carries a significant burden to the patient. Redo-DCR showed a reasonable success rate of 75% in a moderate number of eyes (16), and would not alter the success of subsequent LJT insertion, and is thus the recommended secondary procedure in this failure category.
Mitomycin C (MMC) has been used with increased frequency as an adjuvant therapy in DCR surgery. While it has shown to increase surgical success in endonasal DCR revisions(12-14), this same benefit was not found in external approach redo-DCR(15), and at our institution MMC is not routinely used in these cases, and thus is not included in the flowchart.
Success rates of redo-DCR surgery
Revision-DCR was successful overall in 61% (37/61) for all causes. However, when evaluated based on DCG findings of anatomical failure, rates of success ranged widely from 0% to 100%. When patients are weighing the risks vs. benefits of future surgery, the difference between a 0% or 100% predicted success rate becomes extremely important.
Revision-DCR was least effective in patients with either upper or lower canalicular blockage (0% success) or a normal post-DCR DCG (22% symptom resolution). In patients with normal post-DCR DCG, this poor success rate is likely to reflect the fact that there may be other more proximal points of resistance to flow in the drainage system than at the nasolacrimal duct/anastomosis level.
Previous reports of symptomatic improvement after external redo-DCR range from 78%(6) to 85%(5). As previously discussed, the case mix of these groups influences their success rates and makes comparison with this study’s success rate challenging. Ari et al., reported that redo-DCR had 78% success in patients with recurrent dacryocystitis(6), which presumably was due to complete anastomosis obstruction. Their group of patients is equivalent to the cohort in this study with a complete anastomosis closure, who indeed had similar rates of success after redo-DCR (75%). Welham et al., found a higher rate of success post redo-DCR (85%)(5) in failed DCR cases than this study. It is not clear what proportion, if any, of their patients would have had a DCG consistent with a “normal anastomosis”. We have clearly demonstrated that this group of patients had the lowest success rate after revision DCR surgery. Indeed, these are the patients that surgeons are most reluctant to operate on due to low probable success, which can now be quantified for the patient by reference to this study.
Anastomoses draining into a nasal sinus
Three eyes (1.9%) of 3 patients had their lacrimal sac anastomosed to a nasal sinus rather than the nasal cavity. Unsurprisingly, all 3 patients had external approach DCR, and no tube stents were inserted in 2 cases. Nasal sinus anatomy is highly variable(16). In particular, agar nasi cells (large, anterior ethmoid air cells) are often encountered during DCR surgery. Entering these air cells can be misinterpreted as entering the nasal space, as is the case in Figure 2B. Haller Cells are sinuses inferior to the ethmoid air cells, which extend into the roof of the maxillary sinus. They can drain into either the anterior or posterior ethmoidal sinuses and occur in approximately 20% of people(16). In two cases, the lacrimal sac appeared to drain into Haller Cells (Figure 2A,C). These particular findings demonstrate how a DCG can be useful in planning revision lacrimal surgery by directing the surgeon to create a new anastomosis rather than erroneously enlarging the pre-existing one.
Decision making tool
Medicine is now entering into an era of shared decision making with the use of decision-making tools for patients. For this to be viable, patients need to be presented evidence for and against treatment options in a way that is easy for them to understand and compare. This flowchart (Figure 3) will serve as an invaluable visual guide of surgical success rates and thereby facilitate planning for individualised management.
Benefits of DCGs
Although the cause of DCR failure can often be determined by careful clinical examination and nasal endoscopy, DCGs can identify precise structural abnormalities that would not be recognised through lacrimal irrigation alone. In this study, it identified flow into a nasal sinus, which would only show as reflux on lacrimal irrigation. Furthermore, the classic identification of a hard or soft stop on canalicular probing is absent once bone has been removed during DCR surgery. During lacrimal irrigation, the absence or presence of yellow fluorescein in the regurgitated fluid is dependent on having a large enough residual sac. Therefore, sometimes a common canalicular block and a completely closed anastomosis (with no mucus) are confused without a DCG. Additionally, DCGs can reveal ‘sump’ syndrome or ‘birdbox’ anastomosis with hold up of dye in the sac on the erect x-ray, which is not identifiable on lacrimal irrigation alone.
Although DCGs carry radiation exposure, only 0.0011 to 0.0046Gy(17) is delivered to the lens. In contrast, detectable lens opacities occur from over 100 times this level, at 0.5-2Gy and cataracts occur from 5Gy(18).