Yalçin 2002.

Methods	Study design: randomized, parallel‐group study Conditions included: chronic posterior blepharitis Enrollment: 40 participants  Exclusions and loss to follow‐up: none reported Study follow‐up: 4 months
Participants	Country: Turkey Age: mean 43 years Gender: 12 men and 28 women Inclusion criteria: patients with chronic posterior blepharitis visiting SSK Okmeydani Education Hospital's Eye Clinic
Interventions	Therapy group (43 eyes of 22 participants): 100 mg oral NAC 3 times a day for 8 weeks, plus control treatment Control group (36 eyes of 18 participants): topical steroids (prednisone acetate) and antibiotics (tobramycin sulfate) 4 times daily for 4 weeks, plus warm compresses twice daily for 2 months and artificial tears (polyvidone) 4 times daily for 3 months
Outcomes	Primary outcomes: 1) Schirmer‐1 test increase rate between groups 2) fluorescein BUT increase rate between groups 3) mucus fern test increase rate between groups 4) adverse events Measurements taken at baseline and weekly for 4 months Unit of analysis: the individual (average of both eyes)
Notes	Study dates: not reported Funding source: not reported Declarations of interest: none reported Publication language: English
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of randomization not reported.
Allocation concealment (selection bias)	Unclear risk	Method of allocation concealment not reported.
Masking (performance bias and detection bias) Were participants masked to treatment group?	High risk	Participants could not be masked to differences in treatment groups.
Masking (performance bias and detection bias) Were healthcare providers masked to treatment group?	High risk	Masking not reported.
Masking (performance bias and detection bias) Were outcome assessors masked to treatment group?	High risk	Masking not reported.
Incomplete outcome data (attrition bias) All outcomes	Low risk	ITT analysis was followed.
Selective reporting (reporting bias)	Low risk	Results were reported for primary and secondary outcomes.
Other bias	Low risk