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Table 2 Characteristics of systematic reviews examined

From: Outcome choice and definition in systematic reviews leads to few eligible studies included in meta-analyses: a case study

CharacteristicNumber of systematic reviews (N = 175)
n (%)
Year published
 2003–20053 (2)
 2006–200812 (7)
 2009–201115 (9)
 2012–201468 (39)
 2015–201777 (44)
Population (function/region of eye) addressed
 Retinal/choroidal disease35 (20)
 Visual impairment/low vision33 (19)
 Optic nerve, including glaucoma32 (18)
 Ocular surface31 (18)
 Lens18 (10)
 Ocular vasculature5 (3)
 Other21 (12)
Interventions and comparators examineda
 Drug74 (42)
 Surgery67 (38)
 Other procedure31 (18)
 Device15 (9)
 Supplements6 (3)
 Screening/testing5 (3)
 Other intervention26 (15)
Number of outcome domains examined
 Median6
 Interquartile range5 to 8
 Range1 to 19
Number of primary outcome domains examined
 Median1
 Interquartile range1 to 1
 Range0 to 5
Number of secondary outcome domain examined
 Median4
 Interquartile range3 to 6
 Range0 to 12
Number of other outcome domains examined
 Median1
 Interquartile range0 to 2
 Range0 to 6
Number of studies included
 Median3
 Interquartile range1 to 9
 Range0 to 137
  1. aMore than one category could apply