A light box (10) with a viewing aperture contains sources of illumination (22, 28) which can be adjusted and set to simulate different lighting situations and conditions. An observable image on a trolley (40) is movable e.g. towards and away from the observer (14) and also transversely to the line of sight of the observer. Movement may be effected by stepping motors (36 and 38). Measurements are made of the response of the observer to movement of the image consequent on changes in the parameters affecting the observer's perception of the image. A comparative assessment can thus be made of the effect of changing the illumination. Diffuser panel 24 filter panel 26 and bulkhead plate 34 are shown.
Assessing eyesight using variable lighting and movable image in housing