Abstract
Purpose::
Assessment of functional vision is crucial in management of children with visual impairment to design appropriate educational and rehabilitation intervention strategies. The purpose of this study was to examine functional vision performance (FVP) assessed by self-reports and performance measures in Indian school going children with visual impairment.
Methods::
Performance on 17 daily activities was measured for 178 visually impaired children aged 8-17 years. Subjects also provided ratings of task difficulty on these 17 activities using a reliable and valid questionnaire, the LVP-FVQ (Gothwal et al., IOVS 44: 4131-4139). Rasch analysis of ordinal difficulty ratings was used to estimate interval measures of perceived visual ability for both measures of FVP.
Results::
Children reported the most difficult task as reading a textbook at arm’s length while reading destination details on a bus was observed as the most difficult task on actual performance measure. The mean (± SD) person ability (functional vision ability) from self-report was 0.93 ± 0.68 logits (95% CI of mean = 0.83 to 1.03) versus 1.00 ± 0.90 logits (95% CI of mean = 0.87 to 1.14) on the performance measure; this difference was not statistically significant (p =0.21). There was a significant moderate correlation (r=0.57, p <0.0001) between person ability from self-report and performance measure. For the self-report, there was an excellent correlation between person measures that were derived from Rasch analysis and total FVP score (r=0.96, p<0.0001).
Conclusions::
This study, first-of-its-kind in the field of pediatric visual impairment, further validates the use of LVP-FVQ to assess FVP in Indian children. Self-reports that offer the advantage over performance measures of quicker administration time and simultaneous use on a larger population can be used for assessment of FVP to help in better planning and rehabilitation of visually impaired school-going children in India. A scoring algorithm has been developed for investigators who wish to use LVP-FVQ to facilitate conversion of raw scores into Rasch analysis-derived linear person measures. Children with lower raw scores on the LVP-FVQ (worse functioning) will need referral for low vision services. In doubtful cases the examiner should have the child perform those limited tasks, thereby saving time and resources in a developing country such as India.
Keywords: low vision • clinical research methodology • reading