... 1,6,16,20,39,40,44,50,56,62,69,75,90,93,96,104,110,111,121 In some cases, authors quantified the number of participants with a certain degree of visual impairment, that is, how many participants had visual impairment and how many participants were blind. 32,39,74,85,90,97,108,123 Thirteen studies reported the number of participants that fell into a visual acuity range or reported the visual acuity of each individual participant, 7,8,12,13,15,21,26,27,43,61,78,95,110 whereas 18 studies reported the diagnoses or cause of visual impairment of their participants. 1 studies, participants had visual impairment or blindness caused by various eye conditions. ...