Table 1

Characteristics of studies of vitrectomy alone versus vitrectomy with IVB pretreatment included in the meta-analysis

Trials (first author, year)	Location	Design of trial	Duration (months)	Original patients (eyes)	Dropout patients (eyes)	Mean age±SD (range) (male/female)	System baselines	Ocular baselines	Jadad score
Yeh, 20091	Taiwan	Prospective, comparative case–control clinical study	6	1–: 21 (22) 2–: 20 (21)	1–: 1 (1) 2–: 1 (1)	1–: 51.0±7.7 (8/13) 2–: 49.4±7.9 (11/9)	NS: DM, Systematic hypertension, Renal insufficiency, haemodialysis	NS: Lens status, Prior PRP, BCVA	1
da R Lucena, 20092	Brazil	Prospective, randomised comparative laboratory study	That day	1–: 10 (10) 2–: 10 (10)	0	1–: 55.6±6.7 (46–62) (4/6) 2–: 54.4±5.7 (42–60) (6/4)	NS: DM, HbA1C;RD duration	NS: Prior PRP, BCVA	4
Rizzo, 20083	Italy	Consecutive, randomised prospective study	6	1–: 11 (11) 2–: 11 (11)	0	Total: 52 (24–63)	NR	NS: CS, BCVA	4
Modarres, 20094	Iran	Prospective surgeon-masked randomised clinical trial	7±3.6	1–: 18 (18) 2–: 22 (22)	0	1–: 53.2±11.7 2–: 55.8±11.3	NR	NS: CS, BCVA	4
Ahmadieh, 20095	Iran	Prospective, randomised, double-masked clinical trial	1	1–: 33 (33) 2–: 35 (35)	1–: 15 (15) 2–: 19 (19)	1–: 56.70+10.4 (17/16) 2–: 53.69±11.7 (17/18)	NS: systematic hypertension, renal failure, aspirin consumption, smoking	NS: Prior PRP, VH, BCVA	7
Yang, 20086	Taiwan	Prospective, non-randomised, comparative case study	6	1–: 24 (24) 2–: 15 (16)	0	1–: 50.2±10.9 (10/14) 2–: 44.4±11.4 (8/8)	NS DM; systematic hypertension renal insufficiency	NS: lens status, Prior PRP, BCVA	–
di Lauro, 20109	Italy	Prospective, randomised controlled trial	6	1–: 24 (24) 2–: 24 (24)	0	NR	NR	NS: BCVA, CSS	3

1–, vitrectomy alone group; 2–, vitrectomy with intravitreal bevacizumab pretreatment; BCVA, best-corrected visual acuity; CS, complexity score (classify the severity of PDR); CSS, complexity surgery score; DM, diabetes mellitus; HbA1C, glycosylated haemoglobin A1C; IVB, intravitreal bevacizumab; NR, not reported; NS, not significant.; PRP, panretinal photocoagulation; RD, retinal detachment; VH, vitreous haemorrhage.