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G.M. Cochrane, E.L. Lamoureux, J.E. Keeffe; Impact of Low Vision on Children: Validity and Reliability of a Quality of Life Questionnaire . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4407.
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To determine validity and reliability of a questionnaire (IVI_C) to assess the impact of low vision in children.
Focus groups involving students with low vision, teachers and parents and in–depth interviews with educators in low vision were undertaken to establish face validity. Participants were recruited via an educational vision assessment clinic, parent support groups and visiting teachers. The criterion for participation in focus groups was that students have low vision (<0.5 LogMAR). The focus groups considered the greatest impact of low vision on every day life in the home, school and community. Grounded theory principles were used to identify issues and formulate items for the IVI_C. The IVI_C was administered to low vision students (<0.3 LogMAR) and a normally sighted age–matched control group to determine its content validity. Inter– and intra–observer reliability and administration modes were assessed using Guttman split–half correlations.
Of the 100 focus group participants, 20 were students, 28 parents, 18 teachers and 34 specialist instructors. 7 main themes (school, social and peer acceptance, assistance, family, self–confidence, orientation and mobility and community) were identified from 1209 statements. The resultant 28–item IVI_C was administered to 57 students (33 males), mean age of 12 years (±2.8). The mean distance VA was 0.8 LogMAR (range 0.4–2.1). The mean duration of low vision and educational support were 9.4years (±4.5) and 5.6years (± 3.8), respectively. 24 of the 28 items (86%) were considered relevant by 90% or more of the respondents. 18 items (64%) had responses across the full range of the 5 response categories; the remainder did not record responses on the most difficult/least accepted rating. Only 1 pair of items had Spearman correlation >0.6 indicating minimal redundancy. The increase in IVI_C total score correlated with decreasing years in educational support (r=–0.4; p=0.005), children in younger grades (r=–0.36;p=0.007) and duration of vision impairment (r=–0.25; p=0.07). There was a significant difference between the normally sighted age–matched controls and visually impaired participants on the total score supporting content validity (ANOVA;F=32.9; p<0.001). The Guttman split–half correlation for test–retest, modes of administration (telephone and face–to–face) and interviewer–interviewer were 0.93, 0.82 and 0.77, respectively.
As the IVI_C demonstrated good validity and reliability, the next step is to conduct Rasch analysis on a larger sample to continue its development.
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