RESUMEN
<p><b>BACKGROUND</b>In recent years, computers have been intensively used at home. In contrast to paper-based books and documents, computer screen is self-illuminated with larger screen-background luminance difference, which greatly induces visual discomfort. To compensate for that, one effective solution is to offer an additional background luminance. In this study, we investigated whether and to what extent additional background lighting is needed in looking at a computer display comfortably.</p><p><b>METHODS</b>In this study, 60 healthy children aged from 9 to 12 years and 58 adults aged from 21 to 39 years participated in the experiments. They were asked to choose their most preferred background luminance intensities at three screen luminance levels. The data were analyzed by Matlab (R2012b) and SPSS 20.0.</p><p><b>RESULTS</b>Both children and adult participants selected a non-dark background as their comfortable lighting condition when watching a computer display (children: t (59) = 22.0, P < 0.01, adults: t (57) = 15.5, P < 0.01). Comparatively, children preferred brighter background in general ( F (1,116) = 7.0, P < 0.01). More importantly, participants' preferred background luminance levels were linearly correlated with screen luminance intensities (children: slope = 0.97, R(2) = 0.98; adults: slope = 0.38, R(2) = 1.00).</p><p><b>CONCLUSION</b>These results indicate that varying background luminance to maintain screen-background luminance ratio is beneficial to human visual comfort.</p>