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ObjectivesEndonasal dacryocystorhinostomy (DCR) is a well-established treatment method in patients with nasolacrimal duct obstruction. However, there are a few reports about the overall management of failed endonasal DCR. We investigated the causes and management strategies of failed endonasal DCR.MethodsThis retrospective review included 61 patients (61 eyes) who had undergone revision surgery by the same surgeon after failed endonasal DCR between January 2008 and December 2012. The appropriate revision method was determined after analysis of the etiology of failure by the fluorescein dye disappearance test, nasal endoscopy, lacrimal irrigation, and probing. The criteria for success of the revision surgery were defined by the passage of fluid without resistance upon lacrimal irrigation and normalization of the tear meniscus height.ResultsThe mean duration between the primary endonasal DCR and revision surgery was 15.3 months. The average follow-up period after revision surgery was 12.2 months. The most common cause of endoscopic revision surgery was membranous obstruction. Endoscopic revision surgery was performed in 48 patients, while lacrimal silicone tube intubation under endoscopy was performed in 13 patients. The most common indication for lacrimal silicone tube intubation was functional epiphora. The overall success rate of the revision surgery was 89%.ConclusionThe most common cause of failed endonasal DCR was membranous obstruction. When patients with failed endonasal DCR presented at the clinic, it is important to identify the cause of the failure. Revision surgery could increase the final success rate of endonasal DCR.

Shinorine, a mycosporine-like amino acid (MAA), is a small molecule sunscreen produced in some bacteria. In this study, by introducing shinorine biosynthetic genes from cyanobacteria Nostoc punctiform into Saccharomyces cerevisiae, we successfully constructed yeast strains capable of producing shinorine. Sedoheptulose 7-phosphate (S7P), an intermediate of the pentose phosphate pathway, is a key substrate for shinorine biosynthesis. To increase the S7P pool, xylose, which is assimilated via the pentose phosphate pathway, was used as a carbon source after introducing xylose assimilation genes from Schef fersomyces stipitis into the shinorine-producing strain. The resulting xylose-fermenting strain produced a trace amount of shinorine when cells were grown in glucose, but shinorine production was dramatically increased by adding xylose in the medium. Shinorine production was further improved by modulating the pentose phosphate pathway through deleting TAL1 and overexpressing STB5 and TKL1. The final engineered strain JHYS17−4 produced 31.0 mg/L (9.62 mg/g DCW) of shinorine in the optimized medium containing 8 g/L of xylose and 12 g/L of glucose, demonstrating that S. cerevisiae is a promising host to produce this natural sunscreen material.