This article discusses the need to develop ecologically valid measures of visual functioning and mobility performance in the context of current theories of perceptual functioning and learning, and describes the development of a visual assessment and training program, known as OCULA. An evaluation of the effectiveness of four tasks in predicting initial and final low vision mobility performance demonstrated that the tasks are better predictors of visual performance than are existing clinical measures and that learning can be transferred to real-life mobility situations. The results are interpreted in terms of differentiation theory, and the practical relevance of the approach to the training of low vision clients is emphasized, as is the potential of the system as a research tool.
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