R W Massof
Johns Hopkins University School of Medicine, Lions Vision Center, Wilmer Eye Institute, Baltimore, MD, United States
BACKGROUND. A new vision disability theory organizes daily activities into a hierarchical framework. At the highest level, activities are grouped according to the social objectives they serve: Daily Living, Social, Recreational, Educational, and Vocational. At the second level of the hierarchy, activities are organized according to their behavioral goals (e.g., cook daily meals, manage personal finances, entertain guests). At the lowest level of the hierarchy, specific Tasks are identified (e.g., read recipes, cut food, write a check). Tasks also can be organized into functional vision categories that span all Goals and Objectives: e.g., reading, pattern recognition, localization, visually guided fine motor behavior, mobility.
METHODS. A self-assessment questionnaire was developed within this hierarchical framework. Over 1000 low vision patients were asked to rate the importance of 41 Goals under 3 Objectives (Daily Living, Social, and Recreational). For those Goals given a non-zero importance rating, a difficulty rating was elicited. The patients were also asked to rate the difficulty of performing Tasks under the Goals that were given non-zero difficulty ratings (total pool of 340 Tasks). Thus, each patient received an individualized assessment.
RESULTS AND CONCLUSIONS. Separate Rasch analyses of Goal and Task difficulty ratings identified a single vision disability variable and produced highly correlated estimates on an interval scale (r = 0.72). When Rasch analyses were repeated with Tasks organized into functional vision categories, two variables were identified from principal components analysis: mobility-specific and reading-specific factors. These two variables appear to be governed by visual field dimensions and visual acuity, respectively.
Return to the ISLRR.ORG Home Page
