Methods	Study design: unmasked, multicenter randomized controlled trial Number randomized (total and per group): 151 participants in total, number per group was not reported Eyes of participants were stratified as follows (only one eye per participant randomized): Eyes that had not undergone prior vitrectomy (Group 1): 113 in total, 47 in the standard silicone oil group and 46 in the heavy silicone oil group Eyes that had undergone vitrectomy but without silicone oil injection (Group 2): 38 in total, number per group was not reported Number analyzed (total and per group): Statistical analyses were performed only on group 1 data because the sample size of group 2 was small: total: 101 participants; 49 in the SF6 gas group and 52 in the silicone oil group Exclusions and loss to follow-up: 12 participants in group 1 were excluded, all participants in group 2 were excluded Study follow-up: 36 months Sample size calculation: no
Participants	Country: USA Age (mean ± SD): mean ± SD not reported, median age was 62.1 years (range 25 to 84) for the SF6 gas group and 66.2 years (range 24 to 84) for the silicone oil group Gender: M:F=16:33 for the SF6 gas group and 17:35 for the silicone oil group Inclusion criteria: Participants with proliferative vitreoretinopathy with a classification of at least C-3 grade, at least age 18, visual acuity better than light perception, and sufficient contracture so intraocular dissection was required Exclusion criteria: Participants with uncontrolled concomitant eye disease, occurrence of blunt trauma to the eye within 3 months of randomization, history of penetrating trauma to the eye, presence of a giant tear ≥90°, presence of proliferative diabetic retinopathy, and the existence of any condition that would prevent 3 year follow-up
Interventions	Intervention 1: sulfur hexafluoride gas (SF6): 49 eyes (Group 1), 15 eyes (Group 2) Intervention 2: silicone oil: 52 eyes (Group 1), 23 eyes (Group 2)
Outcomes	The study did not separate primary or secondary outcomes. All outcomes included: visual acuity, retinal reattachment, refraction; development or change in ocular complications affecting the cornea, iris, or lens; and measurements of intraocular pressure at 10 days, and 1, 3, 6, 12, 18, 24, and 36 months following randomization Secondary outcome(s): N/A Time points measurements were taken: 1,3,6,12,18,24, and 36 months
Notes	Study dates: 1 September 1985 to 30 June 30 1991 Funding source(s): trial sponsored by the National Eye Institute. Silicone oil provided by the Dow Corning Corporation Declaration of interests: not reported Publication language: English
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomization scheme generated by the Data Coordinating Center; stratification and blocking methods employed to ensure equal treatment assignments within each clinical center
Allocation concealment (selection bias)	Low risk	Investigators used sealed opaque envelopes supplied in limited numbers by the Data Coordinating Center
Masking of participants and personnel (performance bias)	Unclear risk	No information provided with respect to masking of participants or study investigators
Masking of outcome assessment (detection bias)	High risk	“A surgeon cannot be masked to the treatment during the operative procedure. During follow-up examinations, silicone fluid produces a characteristic appearance in the eye unlike that of a long-acting gas, making it impossible to mask study technicians.”
Incomplete outcome data (attrition bias) All outcomes	High risk	Last observation carried forward method used for missing data, but data inferred only if “consistent” findings for prior and subsequent examinations. Randomized participants from a center that ceased recruitment (n = 12) and randomized participants with a history of prior vitrectomy (n = 38) were excluded from the analysis
Selective reporting (reporting bias)	Low risk	This study appeared to be free of selective reporting. Outcomes were reported in a prior manuscript describing trial design and participant baseline characteristics
Other bias	Unclear risk	The baseline estimated duration of retinal detachment was greater in Group 2 eyes (eyes of participants with prior vitrectomy but without silicone oil injection) randomized to SF6 compared to Group 2 eyes randomized to silicone oil