In this paper, we propose a new approach to designing visual displays for the elderly based on a human vision model, which is represented by three visual properties: the adaptation of eyes to light, spatial sensitivity and the optical transmittance of eyes. The approach is first to generate a mathematical model as a transfer function approximately equal to the human visual system and then to process the original image using image processing techniques according to the deterioration of human vision with age under specific illuminance levels. This paper describes the proposed method and shows the evaluation results. It is demonstrated that the system can be used as a design tools which will aid prototype evaluation of control panels used in consumer product, including shower-toilets with illuminated buttons.