A systems model for low vision rehabilitation is offered as a theoretical framework for understanding the rehabilitation process, to provide a common language and common premises for a science of rehabilitation, and to provide a metric for measuring the need for rehabilitation and the effects of rehabilitation. The model begins with the premise that from the perspective of an objective observer, an individual's life is a stream of activity that can be organized hierarchically. The first level of the hierarchy contains OBJECTIVES of activities (e.g., daily living, education, recreation), the second level contains GOALS of activities (e.g., cooking, self-care, shopping), and the third level contains specific TASKS that constitute the activities (e.g., measuring ingredients, cutting food, reading recipes). Each task can appear under more than one goal; each goal can appear under more than one objective. Goals, and by inference their subordinate tasks, have value to the individual. The subordinate tasks, and by inference their goals, have a level of difficulty for the individual. Difficulty will scale with the severity of visual impairment, value is an independent construct. Considering each goal, the need for rehabilitation will depend on value and difficulty (e.g., unimportant goals or easy tasks do not require rehabilitation). We define REHABILITATIVE DEMAND to be the function of value and difficulty that is monotonic with the individual's need for rehabilitation. Successful rehabilitation will reduce rehabilitative demand (by reducing difficulty and/or by reducing value, e.g., substituting a nonvisual alternative). The details of the low vision systems rehabilitation model will be presented along with a multidimensional scaling technique for deriving the rehabilitative demand metric from value and difficulty ratings.