Kitazawa 1990.

Methods	RCT. Double‐masked. Placebo controlled.
Participants	20 participants with OHT. Racial constitution is not reported. Inclusion criteria: moderate OHT with IOP that has never exceeded 30 mmHg, normal visual field.
Interventions	Timolol 0.5% twice daily. Placebo.
Outcomes	Incidence of glaucomatous visual field defect.
Notes	Allocation concealment deemed likely, based on double‐masked design. Masking not stated but likely. 2 years follow up. Drop‐outs: 2 patients in each group (not adverse‐event related). Both eyes included, analysis both on basis of patient and eye.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Low risk	A ‐ Adequate