We demonstrated sufficient surgical outcomes after En-DCR for the management of dacryocystitis caused by nasolacrimal duct obstruction. We performed a quantitative analysis of the TMH and found that using a dacryoendoscope during lacrimal stent intubation was significantly associated with a decrease in the TMH after En-DCR. We also showed that the reduction of the TMH is significant for managing epiphora.
A multiple regression analysis of the baseline TMH revealed that age was positively correlated with the TMH. Although an association between the TMH and age has been observed for healthy individuals, [26–28] no studies have assessed the association of the TMH with age or other parameters of eyes with nasolacrimal duct obstruction. The positive association between age and TMH may be attributable to the reduction in eyelid laxity. Our results also revealed that body height is mildly associated with TMH. We speculated that body height may be positively associated with the palpebral fissure size and tear volume. Further studies are required to confirm these hypotheses.
As previously reported, SG-BCI is a minimally invasive procedure with a relatively high success rate when used for nasolacrimal passage intubation because the stent can be reliably placed using a dacryoendoscope, which has become a common tool in Japan. [6, 25] We found a greater reduction in the TMH with SG-BCI than with direct stent insertion. We speculated that the lacrimal intubation stent can be precisely placed in the canaliculus, lacrimal sac, and nasal cavity when using a dacryoendoscope; however, the lacrimal intubation stent may be inserted in the luminal epithelium of the lacrimal duct mucosa when the stent is inserted blindly. Incorrect positioning of the lacrimal intubation stent might result in an insufficient reduction of the TMH after surgery. Based on these results, we recommend SG-BCI when placing lacrimal intubation stents in eyes with nasolacrimal duct obstruction during En-DCR.
We also quantitatively evaluated the improvement in subjective symptoms and found that epiphora remained in some patients with anatomical patency. We found that a greater reduction in the TMH was the most important indicator of better improvement in epiphora. The TMH is a quantitative and objective indicator of the severity of epiphora, whereas lacrimal irrigation test results are subjective. We believe that the TMH should be monitored. Furthermore, we believe that surgeons should aim to decrease the TMH of patients who undergo En-DCR. A high baseline TMH was a risk factor for poor improvement. Although a high baseline TMH was associated with a greater reduction in the TMH, it was also associated with a high postoperative TMH, which may be a risk factor for poor improvement in epiphora.
This study revealed that body height was positively associated with better improvement in subjective symptoms. We speculated that the association between body height and improvement in subjective symptoms is related to the surgical procedure. Previous studies have shown that the nasolacrimal duct diameter is significantly associated with the interfrontozygomatic suture distance. [29, 30] Therefore, it is possible that a wider and larger face is associated with a wider nasolacrimal duct diameter. Because it can be inferred that taller patients have larger faces, we hypothesized that the lacrimal sac is also larger. A large nasolacrimal duct leads to a larger anastomotic ostium created by En-DCR, resulting in significantly better postoperative subjective symptoms. Further studies are required to assess the size of the anastomotic ostium during En-DCR and confirm this hypothesis. Previous lacrimal stent intubation and ptosis were also associated with poor improvement in subjective symptoms. However, further studies are required to confirm these results.
This study had several limitations. First, there was a significant difference in the baseline characteristics of patients from the two institutes. The baseline TMH differed between patients from the two institutes because a standard method of measuring the TMH has not been established. Because the TMH is affected by various factors, such as temperature, wind, blinking, and humidity, it is difficult to replicate the TMH under different conditions. Therefore, we used the rate of change in the TMH as the clinical outcome and performed adjustments based on the baseline TMH. Second, phenotyping for conjunctivochalasis or ptosis was subjective. Third, the use of the dacryoendoscope varied between the institutes. Fourth, the current study included patients from only two institutes; therefore, the validity of the results for other institutes is unclear. However, we believe that we clearly demonstrated the usefulness of En-DCR. Nevertheless, this method and its results require replication at other institutes and among other ethnicities.
In conclusion, we demonstrated that En-DCR resulted in good surgical outcomes. We believe that quantitative assessment of TMH using AS-OCT is important and useful for patients who undergo En-DCR. We also demonstrated the usefulness of dacryoendoscopy with lacrimal intubation stents for TMH reduction after surgery, which could become a standardized surgical procedure.