Adequate application of the Lea symbol and BUST visual acuity tests (Hyvarinen et al, 1980 Acta Ophthalmologica 58 507; Lindstedt, 1986 British Journal of Visual Impairment 4 49), designed for children over 18 months of developmental age, in young and/or handicapped pre-school children require preliminary assessment of their level of development. To assess the developmental demands more precisely, 162 children aged from 15 to 35 months and 54 older pre-schoolers, most with normal vision, were examined. Nearly half of the children showed some developmental delays in physical and mental capabilities as assessed on the CDI scale (Ireton, 1992, Child Developmental Inventory, Behavior Science System Inc). Nevertheless, in 77% far and/or near visual acuity was successfully measured by combinations of Lea symbol and/or BUST tests. The youngest successful children, 18 and 20 months of age, passed BUST-N and Lea-Domino. For children aged 18 – 24, 24 – 29, 30 – 35 months, and 36 months and above the success rates were, respectively, 39%, 75%, 89%, and 96%. The minimal values of the CDI scale indexes among the successful children may be regarded, in addition to chronological age, as minimal developmental demands, ie conditions necessary, although not always sufficient, for the child to pass visual acuity measurements. These values in months were 16 (‘social’), 18 (‘selfserving’), 14 (‘gross motor’), 16 (‘fine motor’), 16 (‘speech development’) and 19 (‘language comprehension’). The value of the last index was the most critical. Since the developmental demands are not very high, there are good prospects of using Lea symbol and BUST tests in young and/or handicapped children.
