Blankenship 1979.

Methods	Study design: within‐person RCT. 1 eye randomly assigned to argon laser treatment, the other remained untreated Number of centres: not reported Setting: USA Period: June 1973 to 1975 Sample size: not reported Follow‐up: 2 years
Participants	39 participants (78 eyes). 1 year after: 35 participants (70 eyes) Mean age: 59.7 years Sex (M:F): 23:16 Inclusion criteria: aged ≤ 75 years, documentation of diabetes mellitus. Eyes had to have BCVAs of ≥ 20/100, no more than 3 lines of difference between the 2 eyes, both eyes had to have clear enough means for fundus photography and laser photocoagulation, be phakic, and have macular oedema. Exclusion criteria: neither eye could have previous photocoagulation or PDR. Type of DMO: diffuse and cystoid
Interventions	Argon laser photocoagulation (39 eyes) versus no treatment (39 eyes)
Outcomes	Changes of VA
Notes	Funding: not reported Conflict of interest: not reported Trial registration: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Low risk	Sealed cards
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Optometrist unaware of the eye assignments
Incomplete outcome data (attrition bias) All outcomes	High risk	Loss > 20%
Selective reporting (reporting bias)	Unclear risk	No protocol available
Other Bias	Unclear risk	Not reported