Reading with magnifiers.

The design of low vision aids for partially sighted people, such as magnifiers, is evaluated theoretically in order to identify meaningful directions of research for improving these aids. Both reading with and without a magnifier involves alternating sequences of locating and recognizing textual information. Little is known, however, about these processes in magnifier reading. On the basis of an extensive review of the literature, two topics are identified that stand out as being in need of experimental investigation: (1) the relationship between the (typo)graphical characteristics of printed text and the location and recognition of textual information, and (2) the interplay of location and recognition processes in magnifier reading, including the role of non-visual factors, such as movements of the hand, trunk, head and eyes in this interplay. With regard to the first topic, it is expected that the visibility and, hence, the recognition of textual information by partially sighted people can be improved by matching the fundamental spatial frequencies of graphical structures with the spatial contrast sensitivity of partially sighted people. With regard to the second topic, it is argued that persistent problems in the design of the magnifiers, such as the optimal window size, can only be resolved by studying reading with a magnifier as a (multimodal) perceptual-motor activity.