Leino 1992.

Methods	Parallel‐group RCT
Participants	195 participants with seasonal allergic conjunctivitis
Interventions	Three treatment arms: nedocromil sodium 2%; sodium cromoglycate 2%; placebo. Duration of treatment 4 weeks
Outcomes	Overall assessment by participants and investigators using a 4‐point scale
Country	Finland
Number randomised, gender (male:female)	195 participants randomised, 185 participants analysed. M:F not stated
Age mean (SD), median, range	Mean: nedocromil 20.8 years; sodium cromoglycate 19.3 years; placebo 19.7 years
Notes	Not reported when study was conducted. Source of funding not stated. Declaration of interest by the authors was not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method used to conceal the allocation sequence was not described
Allocation concealment (selection bias)	Low risk	(p.930 ‐ material and methods): "After 1‐2 weeks the patients were issued their appropriate eye drops by randomized code number..."
Incomplete outcome data (attrition bias) All outcomes	High risk	Withdrawal/exclusion of participants (p.931 ‐ results): "Data were returned from 195 patients, 10 of whom withdrew without taking test treatment and were excluded." "A further 12 patients (5 nedocromil sodium, 3 sodium cromoglycate and 4 placebo) withdrew from the study without completing the 4‐week treatment period."
Selective reporting (reporting bias)	Low risk	Evidence was available of proper outcome reporting
Other bias	Low risk	No apparent evidence of other risk of bias
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Identical drugs packaging (p.930 ‐ medication): "All test drugs were supplied in identical 10 ml plastic bottles."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Identical drugs packaging (p.930 ‐ medication): "All test drugs were supplied in identical 10 ml plastic bottles."