Tirakunwichcha 2011.

Methods	Study design: randomized controlled trial, parallel group Unit of analysis: participants Number randomized: 50 in total, 26 in the MMC group, 24 in the EN‐DCR alone group Number of arms: 2 Enrollment start year: 2004 Length of follow‐up: 12 months Sample size calculations: not reported Losses to follow‐up: none
Participants	Country: Thailand Age (mean (SD)): 44.6 (NR) in total, 44.3 (6.47) in the MMC group, 44.9 (6.87) in the EN‐DCR alone group Females (n (%)): 41 (82) in total, 22 (84.6) in the MMC group, 19 (79.2) in the EN‐DCR alone group Inclusion criteria: patients with primary acquired nasolacrimal duct obstruction Exclusion criteria: secondary causes of obstruction and canalicular obstructions Study group differences: no differences
Interventions	Intervention: EN‐DCR with application of 0.5 mg/mL MMC Comparison intervention: EN‐DCR with application of placebo
Outcomes	Measured outcomes: functional success, defined as disappearance of the tearing anatomic success, defined as patency to lacrimal irrigation via syringing irrigation without fluid reflux ostium size on nasal endoscopy at 6 months postoperatively Adverse events: none
Identification	Author name: Suppapong Tirakunwichcha Institution: Chulalongkorn University Email: suppapong.t@chula.ac.th
Notes	Funding source: not reported Declarations of interest: not reported Trial registration number: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants were randomized using a "block of four randomization, which was prepared in advance and concealed in 50 envelopes (in chronological order) by an independent ophthalmologist".
Allocation concealment (selection bias)	Low risk	"The patients were then allocated into the treatment group .... using the block of four randomization, which was prepared in advance and concealed in 50 envelopes (in chronological number) by another ophthalmologist (S.S.) who was not involved in the surgical process and outcome evaluation."
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"Double‐masked" study: "The 0.5 mg/ml mitomycin C solution and the placebo were prepared in the same color for each patient by the assigned scrub nurse who cooperated with the ophthalmologist (S.S.) who knew which group the patient was in, and the solution was served to the surgeon in the operating field. The endonasal endoscopic DCR was performed by the otolaryngologist (A.S.). The surgeon was masked to the intervention and only yielded to assess the outcomes."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Postoperative eye symptoms were assessed by the ophthalmologist (TS), and ostium sizes were measured by the otolaryngologist (AS). The collected data gathered by the ophthalmologist (SS) were disclosed after the 1‐year follow‐up visit.
Incomplete outcome data (attrition bias) All outcomes	Low risk	There were no missing outcome data.
Selective reporting (reporting bias)	Unclear risk	No trial or protocol registration available for comparison to ascertain selective outcome reporting.
Other bias	Unclear risk	There was insufficient information to permit a judgement of 'low risk' or 'high risk'.