Methods for Measuring Personal Costs Associated With Vision Impairment

Abstract

Purpose: To describe and evaluate the procedures used to collect personal costs associated with vision impairment using diaries. Methods: Participants with impaired vision (VA < 6/12 or ≥ 6/12 with restricted visual fields) were recruited. Twelve-monthly diaries, provided in large print and electronic format (with audio and Braille instruction manuals and personal assistance), were used to record vision-related expenditures grouped under four categories. Two questionnaires were used to collect additional information and to test the validity of the self-reported costs. Results: Of 227 people who consented to participate, 66% (n = 150; 91 females; mean age = 64.8 years) completed ≥ 3 monthly diaries. Of the 150 eligible participants, 68% completed the diaries over 12 months, indicating a relatively high completion rate. The median total cost was AUD$2,417 per annum and median values for the four expenditure categories ranged between AUD$206 and AUD$872 per annum. The data were consistent across different months with no significant difference found between any monthly comparison (t-test; p > Bonferroni-adjusted value). Data at 1, 3, and 6 months, extrapolated to annual figures, showed no significant difference from annual total costs, indicating consistency in the data collection periods. A significant association was found between diary data and similar entries in the follow-up questionnaire, confirming the validity of the recorded expenditures (Spearman; p < 0.01). Participants commented that the diary method was useful to obtain personal costs. Conclusion: A high response rate was achieved by using diaries and additional assistance methods. The diary provided an accurate and reliable strategy to determine the major personal costs associated with vision impairment.