Study	Visual acuity	Minimum vision improvement with full correction	Difference between the spherical equivalent of the right and left eyes (anisometropia) D = dioptres	Minimum uncorrected spherical refractive error	Astigmatism D = dioptres
Congdon 2011	6/12 or worse in either eye (presenting)	2 or more lines in either eye
Morjaria 2016	Worse than 6/9 in better eye (presenting)	2 or more lines in better eye	1 D or less		Spherical equivalent corrects the visual acuity to not more than one line less than best corrected visual acuity with a full prescription in the better eye
RECS 2009	6/12 or worse in better eye (presenting)		Less than 2 D myopic Less than 1 D hyperopic	1 D or more	Less than 2 D
SIL 2014	6/12 or worse in either eye (uncorrected)	Better than 6/12 with spectacles
SIL II 2015	6/12 or worse in either eye (uncorrected)			"refractive error meeting cutoffs shown to be associated with significantly greater improvement in visual acuity when corrected: myopia <0.75 diopters (D), hyperopia >þ2.00 D, or astigmatism (nonspherical refractive error) >1.00 D."
WEAR 2017	6/12 or worse in both eyes (presenting)	Better than 6/7.5 in both eyes	Less than 2 D	‐1.00 D or less	Less than 2 D
Wedner 2008	Worse than 6/12 in either eye (presenting)