Jampol 1983.

Methods	Randomised, multicentre, parallel, open‐labelled design.
Participants	167 eyes of 122 participants with Hb SC, Hb SS and Sβ thalassaemia. Chicago: 64 eyes. Kingston: 103 eyes. Males = 60, females = 62. Age 13 to 67 years.
Interventions	Unit of allocation was the eye. Chicago Feeder vessel photocoagulation (n = 34) using Coherent Radiation Model 800 Argon laser through 3 mirror lens. 500 µm spot size, 0.2 second duration and 300‐800 mW power. Control group (n = 30): no photocoagulation. Kingston Feeder vessel photocoagulation (n = 53) using O'Malley Log 2 xenon arc photocoagulator with a direct ophthalmoscope delivery system without contact lens. intensity 5 ‐ 10, size 3 ‐ 6, duration 0.5 ‐ 2 seconds. Control group (n = 50): no photocoagulation. Between 1 to 5 laser sessions given in both centres.
Outcomes	1. Complete closure of neovascularization 2. Visual acuity decreased by 3 lines of the Snellen chart 3. Vitreous haemorrhage 4. Retinal detachment 5. Choroidal neovascularization Chicago: trial period ‐ October 1977 to January 1982. Follow up ‐ mean 21.3 months (range 0 ‐ 52 months) Kingston: trial period ‐ April 1978 to September 1980. Follow up ‐ mean 32.0 months (range 0 ‐ 46 months)
Notes	Supported partly by Comprehensive Sickle Cell Center grant from National Heart, Lung and Blood institute and National Institute of Health, Bethesda, Maryland.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: " patient with unilateral neovascularization ... were randomly assigned (by computer randomisation) to either photocoagulation or the control group." "patient with bilateral neovascularization, right eye was randomized and left eye was given alternate modality".
Allocation concealment (selection bias)	Unclear risk	Not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Chicago: 2 participants were lost to follow up and 1 refused to co‐operate. Kingston: 8 participants were lost to follow up due to emigration and 2 refused to co‐operate. Trial analysed all eyes as randomised.
Selective reporting (reporting bias)	High risk	The trial did not clearly state the pre‐specified outcomes in methods section, and the outcome 'regression of new blood vessel' was reported only for the treatment group, not for the control group.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Blinding was not mentioned in the methods section, it is an open‐labelled trial but performance bias is unlikely with an intervention of this nature.
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 demonstrate non‐inferiority of laser photocoagulation for primary outcomes.

RCT: randomised controlled trial
 Hb SC: sickle cell haemogloin C
 Hb SS: homozygous sickle cell disease
 µm: micrometre