In the present long-term follow-up study, we demonstrated that silicone tube intubation after transcanalicular MDP of less than 3 months was significantly more frequently associated with recurrence. To our knowledge, the present study is the first to evaluate the relationship between silicone tube intubation duration and recurrence in patients undergoing transcanalicular dacryoplasty over such a long follow-up period.
Our results confirm the widespread expert opinion that a tube intubation of at least 3 months is recommended for transcanalicular recanalizing microendoscopic procedures, particularly microdrill dacryoplasty. Intubating over a longer period of time, however, does not seem to show any further benefit and might also lead to biofilm formation. Pathophysiologically, endoscopic recanalization is thought to cause perioperative micro-injuries to the nasolacrimal mucosa itself, which would otherwise result in scarring and adhesions during the healing process in the absence of intubation, leading to re-obstruction.
The major advantages of minimally invasive methods represent endoductolacrimal visualization, the possibility of classifying the type of obstruction as well as sight-controlled recanalization and preservation of all involved structures of the lacrimal apparatus. The risk of complications and bleeding is significantly reduced compared to DCR7. However, a disadvantage compared to DCR is the reduced long-term success rate. While long-term data on DCR show a success rate of around 90%, the only publication with a similar follow-up period after transcanalicular dacryoendoscopy showed a success rate of just under 60%, although the initial success rate was 84%11. When comparing success rates of different studies on nasolacrimal duct surgery, the definition of success and the careful and correct indication for the performance of microendoscopic procedures need to be reviewed critically11. In our study only a complete resolution of epiphora (corresponding to a Munk score of grade 0) was defined as success.
Moreover, the pathogenesis of PANDO, the main indication for endoscopic procedures, is still not yet fully understood. It may be assumed that due to chronic inflammation and vascular congestion resulting in fibrous obstruction a minimally invasive procedure might not prevent a re-obstruction over the years. The pathophysiology of so-called functional obstruction, i.e. epiphora despite anatomically free irrigation, has also not been clarified with certainty and could have contributed to the increased incidence of the reported recurrence14,15,16.
Lee et al. also showed that the type of obstruction has significant influence on the success rate17. They included 156 patients undergoing lacrimal duct endoscopy and distinguished between PANDO with secretory (mucus, stones, granulation) and structural (membrane) obstruction. The success rate after 6 months was significantly higher for the structural (95.3%) than for the secretory type of obstruction (79.9%, p = 0.001). Success was defined as a Munk score of 0 to 1 with concomitant tear film meniscus height of < 300 µm and a passed irrigation test after tube extubation. No microdrill or laser was used in this study, so it can be speculated to what extent recanalization by microdrill or laser has an advantage over “blunt” recanalization with the endoscopic probe. For this purpose further studies are desirable in order to aim for a uniform approach of treating NLDO.
There are several limitations of the present study worth noting. First, our study has a retrospective design, therefore we cannot subsequently distinguish between PANDO with either secretory or structural obstructions and comment on the possibly different outcomes. Nevertheless, our patient population is quite homogeneous since we only included patients with PANDO and without previous lacrimal duct surgery. Second, differences in the occurrence of recurrence may also be due to demographic, behavioral, and clinical differences between patients because of the absence of a standardized protocol during the follow-up period. A prospective, randomized, study design could provide clarity. Further studies with a prospective design are needed for this purpose. Furthermore, no conclusions can be drawn regarding the anatomical patency of the LDS, since we did not perform irrigation of the LDS at the time of the follow-up. However, measuring success by patient satisfaction and resolution of symptoms is a widely used tool in the evaluation of nasolacrimal duct surgery and the most important factor for patient satisfaction18,19.
In conclusion, our results suggest that an intubation duration with a silicone tube of less than 3 months might lead to a higher incidence of recurrence in patients after transcanalicular MDP. Taken these findings into account and carefully considering the indications including the type of obstruction, endoscopic dacryoplasty is a minimally invasive procedure which is well suited as a first-step procedure.