Modarres 2009.

Methods	Prospective, single‐masked (surgeon), randomised clinical trial Country: Iran
Participants	Number: 40 Age: Mean (± SD). Intervention group 55.8 (± 11.3) and control group 53.2 (± 11.7) Sex: Not given Inclusion criteria: Diabetics who were candidates for vitrectomy Exclusion criteria: Presence of significant cataract to cause impairment of vision Previous IVB injection Other vitreoretinal pathology: past history of uveitis, retinal artery or vein occlusion Follow‐up: Mean follow‐up 7 ± 3.6 months
Interventions	Intervention: IVB injection (2.5 mg) 3 to 5 days before operation (n = 22) Comparator: No treatment (n = 18)
Outcomes	Primary outcome measure: Facilitation of surgery and decrease in complications Secondary outcome measure: Anatomic and visual outcomes at 6 months Follow‐up: Mean follow‐up 7 ± 3.6 months
Notes	Trial registration number: not reported Date study conducted: not reported Funding: not reported Conflict of interest: reported that there were none
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"40 eyes of 40 diabetic participants who were candidates for vitrectomy were randomly assigned to receive ..."
Allocation concealment (selection bias)	Unclear risk	Not stated in report
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not stated in report
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	"The surgeons were masked as to the injection", but not clear if the outcome assessors were masked
Incomplete outcome data (attrition bias) All outcomes	Low risk	Not stated in report, however clear from the results that all participants completed follow‐up
Selective reporting (reporting bias)	Low risk	All data discussed within the primary outcome for facilitation of surgery were analysed