Considerable increase in eye strain has been the consequence of the introduction of modern techniques, not only in industry but also in the service sector (banking, insurance, public utilities, hospital administration). This strain is due to both the increase in miniaturization (characteristic of electronics and watchmaking, but also part of the service sector as scientific and technical papers are filed on microfilms or microfiches which must be read with the aid of projection systems) and the enormous expansion of information processing and the use of computers.
With cathode-ray tube (CRT) screens, video screens, microreaders and mounting tables illuminated from below, characters displayed are bright against a dark background. The display (often produced by projection of electrons onto a fluorescent screen) differs considerably from the temporal and spectral conditions pertaining to the reading of printed documents. Also, the text is presented on an almost vertical surface placed at a fixed distance and subject to reflective glare.