The Activity Inventory: an adaptive visual function questionnaire.

Purpose: The Activity Inventory (AI) is an adaptive visual function questionnaire that consists of 459 Tasks nested under 50 Goals that in turn are nested under three Objectives. Visually impaired patients are asked to rate the importance of each Goal, the difficulty of Goals that have at least some importance, and the difficulty of Tasks that serve Goals that have both some importance and some difficulty. Consequently, each patient responds to an individually tailored set of questions that provides both a functional history and the data needed to estimate the patient's visual ability.

Visual disability variables. II: The difficulty of tasks for a sample of low-vision patients.

Objectives: To test the validity and reliability of measures of visual ability and to evaluate the relation between measurements made at the task level and measurements made at the goal level of a hierarchical model for visual disability.

Design: Validation of a telephone-administered functional assessment instrument using Rasch analysis on self-assessment ratings.

Setting: Telephone interviews of respondents in their homes.

Visual disability variables. I: the importance and difficulty of activity goals for a sample of low-vision patients.

Objective: To test the validity and reliability of latent trait measures estimated from ratings by low-vision patients of the importance and difficulty of selected activity goals.

Design: Validation of a telephone-administered functional assessment instrument using Rasch analysis of self-assessment ratings.

Setting: Telephone interviews of respondents in their homes.