Table 2.

 Visual screening methods and outcome measures

Reference	Visual screening method	Visual outcome measure
Vetter 1984w3 (UK)	Two questions about glasses and difficulty seeing	Proportion with positive response to question “Do you have any difficulty seeing (even when wearing your glasses)”
McEwan 1990w9 (UK)	Series of questions about vision and glasses	Proportion who “always” or “quite often” had difficulty reading ordinary newsprint (with glasses if worn)
Vetter 1992w13 (UK)	As Vetter 1984, with additional question about recent eye test	As Vetter 1984w3
Van Rossum 1993w14 (Netherlands)	One question “How do you assess your vision at present?” Possible answers: excellent, good, fair, not so good, or bad	Proportion answering “fair,” “not so good,” or “bad” to screening question at end of study
Wagner 1994w16 (US)	Simple questions about visual function and use of glasses in postal questionnaire	Proportion reporting visual problems on repeated mailed questionnaire at 2 years