Visual field expanders.

Diminishing telescope systems designed to widen the field of view of patients with tunnel vision are described. Theoretical analysis suggests that telescope systems will greatly improve visual search times and diminish the difficulties of such patients. This can be considered quantitatively, and it is suggested that the optimum amount of minifying power can be calculated by applying established formulations on visual efficiency. The inadequacies of previous designs have inhibited development, and further improvements to bioptic systems may be necessary before the final assessment of the clinical value of these devices can be made.