Reading ability and reading engagement were assessed using a questionnaire administered orally to subjects during an in-person interview containing 10 different reading items: magazines, newspaper articles, bills, financial statements, handheld menus, religious texts, books, word puzzles, typed mail, and written notes or mail. The 10 reading items used in our questionnaire were taken from the Activity Inventory (AI), a visual function questionnaire developed and validated by Massof et al.
16 to measure visual ability in patients with low vision. The 10 AI reading tasks were chosen to provide enough breadth and variety to cover the varying levels of reading ability among our subjects. For each activity, subjects first were asked how important the activity was to them. The importance response categories were: “not important,” “somewhat important,” “moderately important,” and “very important.” If the subject responded “not important,” then the interviewer moved on to the next task. If the task was rated with any other importance category, then the subject was asked to rate the difficulty of that reading task without the assistance of another person. The difficulty response categories were: “not difficult,” “slightly difficult,” “moderately difficult,” “very difficult,” “extremely difficult,” and “impossible.” Based on a previous Rasch analysis of the six rating categories used by a large sample of low vision patients,
16 we merged two categories and assigned rank scores to the response categories as follows: 3, “not difficult”; 2, “slightly or moderately difficult”; 1, “very or extremely difficult”; and 0, “impossible.” When participants were asked to rate the difficulty of these reading tasks, they were assigning a rating to the magnitude of the difference between their reading ability and the ability level required by the task. Therefore, reading ability is a function of the difficulty ratings assigned to a series of different reading tasks, which was estimated by the Rasch analytical model.
Reading engagement was defined as the rate at which participants engaged in a particular reading activity in an average week. To evaluate reading engagement, subjects were asked to state how many days out of a typical week they perform each of the 10 reading activities that they deemed to be at least slightly important.