Patients with age-related visual loss suffer reduced ability to recognize faces and other scenes in photographs and on television. Recently, progress has been made in image enhancement, using controlled distortion of digitally stored images that increases their usefulness in particular applications. Described are two approaches to image enhancement for the visually impaired. In one approach, the visual losses that characterize individual patients and disease classes are described using detailed measurements of visual degradation transfer functions, which are profiles of loss of image information at various spatial scales. The particular distortion used for image enhancement is then adjusted to the impairment of the individual patient or disease class. A second approach takes advantage of the resemblance between the visual losses of many patients and the degradation of picture information in other applications due to external limitations (e.g., fog and haze) on photography. Several enhancement algorithms have been found useful with such images and may also improve picture recognition by the visually impaired.
Accessibility of shared space for visually impaired persons: A comparative field study