A R Bowers¹, J E Lovie-Kitchin², A M Y Cheong²
¹Schepens Eye Research Institute, Research Associate, Boston, United Kingdom; ²Queensland University of Technology, Centre for Eye Research, Brisbane, Australia
Background
Previous studies have primarily considered the effect of field of view on page navigation with CCTVs. In this study we investigated the effect of a range of vision and magnifier variables on forward and retrace navigation performance when reading with optical magnifiers.
Methods
Magnifier movements (X, Y and Z) were recorded using a 3SPACE Isotrak system whilst 20 visually impaired subjects used their habitual hand-held or stand magnifier to read a short story (90 words) and to perform a simple test of page navigation skills. Forward and retrace navigation times were determined and navigation errors were quantified.
Results
There was a highly significant relationship between near word acuity and forward navigation time for the reading task (r = 0.8, p < 0.001), but there were no significant correlations (p > 0.05) between vision measures and retrace navigation time. Navigation performance in the simple test was predictive of navigation performance during passage reading. Patterns of magnifier usage, magnifier experience, magnifier characteristics and subjective estimates of page navigation difficulties were not predictive (p > 0.05) of page navigation performance. There were no significant predictors of the number of navigation errors.
Conclusions
Visual acuity was the strongest predictor of forward navigation time, but none of the variables considered in this study were significant predictors of retrace navigation time. It is possible, however, that other factors such as motor abilities and hand-eye coordination might have a significant effect on retrace navigation performance when using optical magnifiers.
Research supported by small grant from Department of Vision Sciences, Glasgow Caledonian University.
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