This paper employs a regional partition approach to establish the optimal distribution of the diffuser dots in the light guide of an edge-lit backlight. The proposed approach commences by dividing the light guide into a number of partitions and assigning an equal radius to every dot. An iterative optimization procedure is then performed in which the illuminance in each partition is calculated and the dot radius in each partition progressively adjusted until uniform luminance is obtained over the entire light-guide surface. To simplify the geometry construction process and improve the efficiency of the optimization procedure, a simple optical model is proposed for the diffuser dots and the bare surface of the light guide, and an analytical procedure is implemented to take account of the diffuser-film and brightness-enhancement-film effects. The simulation results confirm the ability of the proposed approach to accurately reflect the fine regulation of the dot radius required to obtain uniform luminance for typical light-emitting diode configurations used in practical backlight modules.