Reading speed through different equivalent power low vision devices with identical field of view

Adequate reading speed is one of the criteria low vision patients may use to assist them when they are comparing and selecting equivalent power low vision devices. Inherently, various optical devices of equivalent power will produce different fields of view. We compared the reading speed of 32 trained, normal observers with 4 commonly prescribed types of low vision devices of +12 D equivalent power (spectacles, hand magnifier, stand magnifier, and telemicroscope) which were modified to provide nearly identical fields of view. Our results show that only the reading speed obtained with the telemicroscope was significantly different from those of the other systems (p less than 0.01). Implications are that the field of view provided by a low vision device is the primary parameter limiting reading speed of equivalent power devices.