Farber 1991.

Methods	RCT, single centre, parallel, open‐label design.
Participants	174 eyes of 116 participants. Males: 61 (52.6%); females: 55 (47.4%). Hb SC = 93 (80.2%), Hb SS = 21 (18.1%), Sβ thalassaemia = 2 (1.7%). Age: 16 to 60 years.
Interventions	Unit of allocation was the eye. Sectoral scatter laser photocoagulation (n = 99) using Argon blue‐green laser (Britt model 3250) through 3 mirror lenses. Spot size 500 µm, 0.1 second duration. Burns were placed approximately one burn diameter apart, placed from 1 disc diameter anterior and posterior to sea fan, 1 clock hour to each sides without treating sea fans or feeder vessels directly. Additional laser administered one week later if necessary. Control group: (n = 75) no laser photocoagulation.
Outcomes	1. Regression of neovascularization. 2. Development of new sea fan. 3. Visual acuity decreased by 3 lines of the Snellen chart 4. Vitreous haemorrhage 5. Retinal detachment Trial period: February 1982 to January 1989, follow up; mean 47.4 months (5 ‐ 99 months), for treatment group, 42.4 months (5 ‐ 75 months) for control group.
Notes	This trial was funded by Comprehensive Sickle Cell Center grant and by training grant and core grant from National Eye Institute, National Institute of Health, Bethesda and by unrestricted grants from Research to Prevent Blindness Inc, New York, NY.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: " patients with bilateral disease had their right eye randomized to either scatter photocoagulation or no treatment, with other eye receiving opposite modality". " ..we randomized three of every four eyes in unilateral cases to treatment group". "computer‐ generated randomisation".
Allocation concealment (selection bias)	Unclear risk	Not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "..174 eyes were included in the study (99 for treatment and 75 for control) and 11 patients moved after average of 24 months (range 11‐60 months) and one patient died after 15 months". Trial analysed all eyes as randomised although 11 participants moved out and 1 died.
Selective reporting (reporting bias)	Low risk	Trial did not clearly state the pre‐specified outcomes under the methods section, but all the expected outcomes were reported.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Blinding was not mentioned in the methods section, it is an open‐label trial but performance bias is unlikely with this type of intervention.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	All the outcomes reported were objective.
Other bias	Unclear risk	The trial was possibly under powered to be able demonstrate non‐inferiority of laser photocoagulation for the primary outcomes.