The development of the LV Prasad-Functional Vision Questionnaire: a measure of functional vision performance of visually impaired children.

PURPOSE: To develop a reliable and valid questionnaire (the LV Prasad-Functional Vision Questionnaire, LVP-FVQ) to assess self-reported functional vision problems of visually impaired school children.
METHODS: The LVP-FVQ consisting of 19 items was administered verbally to 78 visually impaired Indian school children aged 8 to 18 years. Responses for each item were rated on a 5-point scale. A Rasch analysis of the ordinal difficulty ratings was used to estimate interval measures of perceived visual ability for functional vision performance.
RESULTS: Content validity of the LVP-FVQ was shown by the good separation index (3.75) and high reliability scores (0.93) for the item parameters. Construct validity was shown with good model fit statistics. Criterion validity of the LVP-FVQ was shown by good discrimination among subjects who answered "seeing much worse" versus "as well as"; "seeing much worse" versus "as well as/a little worse" and "seeing much worse" versus "a little worse," compared with their normal-sighted friends. The task that required the least visual ability was "walking alone in the corridor at school"; the task that required the most was "reading a textbook at arm's length." The estimated person measures of visual ability were linear with logarithm of the minimum angle of resolution (logMAR) acuity and the binocular high contrast distance visual acuity accounted for 32.6% of the variability in the person measure.
CONCLUSIONS: The LVP-FVQ is a reliable, valid, and simple questionnaire that can be used to measure functional vision in visually impaired children in developing countries such as India.