Ragab 2012.

Methods	Study design: randomized controlled trial, parallel group Unit of analysis: participants Number randomized: 76 in total, 38 per group Number of arms: 2 Enrollment start year: 2004 Length of follow‐up: 12 months Sample size calculations: "A sample size of 70 procedures was calculated at the 5% level of significance to give the study a statistical power of 80%" Losses to follow‐up: at 12 months: 3 lost in the MMC group, 2 lost in the control group
Participants	Country: Egypt Age (mean (SD)): 43.6 (10.4) in total Females (n (%)): 49 (64.5) in total Inclusion criteria: patent canaliculi, normal eyelid function, no suspected lacrimal sac neoplasia, no nasal pathology, recurrent acquired complete nasolacrimal obstruction after single endoscopic DCR, duration of persistent symptoms more than 1 year after the primary surgery Exclusion criteria: canalicular or common canalicular obstruction ascertained with probing, noticeable lower lid laxity, age younger than 18 years, Down’s syndrome, suspicion of malignancy, radiation therapy, post‐traumatic bony deformity, and bone diseases Study group differences: no significant difference in demographics
Interventions	Intervention: revision EN‐DCR with application of 0.5 mg/mL MMC during surgery Comparison intervention: revision EN‐DCR
Outcomes	Measured outcomes: functional success, defined as the relief of epiphora anatomic success, defined as patency to lacrimal irrigation minor adverse events Adverse events: minor epistaxis, minimal synechia
Identification	Author name: Sameh M Ragab Institution: Department of Otolaryngology, Tanta University Hospitals Email: sragab@doctors.org.uk
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	Randomization was done using random blocks.
Allocation concealment (selection bias)	Low risk	"The group assignment was placed in consecutively numbered envelopes, which were allocated to the successive cases in chronological order. The envelope was opened on the day of the operation. During the follow‐up period, the patient was assigned to a different investigator. The patient file was coded and linked to a study sheet. The study sheet summarized all the information related to the patient except the operative data. The sheet was copied and added to the patient file after each session, whereas the original sheet was kept in the study folder."
Blinding of participants and personnel (performance bias) All outcomes	Low risk	“At the time of randomization and during the follow‐up period, both the patient and the investigator were unaware of the group assignment. The group assignment was placed in consecutively numbered envelopes, which were allocated to the successive cases in chronological order. The envelope was opened on the day of the operation. During the follow‐up period, the patient was assigned to a different investigator. The patient file was coded and linked to a study sheet. The study sheet summarized all the information related to the patient except the operative data. The sheet was copied and added to the patient file after each session, whereas the original sheet was kept in the study folder.”
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Masking of outcome assessors was not described.
Incomplete outcome data (attrition bias) All outcomes	Low risk	There were no missing data at 6 months (primary endpoint). At 12 months, 3 in the MMC group and 2 in the control group were lost to follow‐up.
Selective reporting (reporting bias)	Unclear risk	No trial or protocol registration available for comparison to ascertain selective outcome reporting.
Other bias	Low risk	Study appears to be free of other sources of bias.