RT Journal Article SR Electronic T1 Preschool vision screening JF British Journal of Ophthalmology JO Br J Ophthalmol FD BMJ Publishing Group Ltd. SP 421 OP 421 DO 10.1136/bjo.81.5.421a VO 81 IS 5 A1 G V CATFORD YR 1997 UL http://bjo.bmj.com/content/81/5/421.2.abstract AB