Improved reading performance using individualized compensation filters for observers with losses in central vision.

By boosting the amplitudes of the intermediate spatial frequencies more than the amplitude of the lower spatial frequencies, reading performance improved significantly when observers with losses in central vision read words that were filtered. Words that were filtered using an image enhancement function based on an observer's losses in visual function relative to a normal observer (1) reduced the magnification (30-70% less magnification was needed) and (2) increased the reading rate (2-3 times), measured in words per minute. The greater the loss in central visual function, the more individualized compensation filters reduced the magnification needed for word recognition. Individualized compensation filters improved the clarity and visibility of words for low vision observers. This study also found that the shape of the enhancement function was important to determine the optimum compensation filter for improving reading performance. In addition, the individualized compensation filters can be implemented by inexpensive hardware, for example in a closed circuit television (CCTV), to provide a significantly more effective low vision aid for observers with losses in central vision to read text, than is provided using only magnification.