There is provided a method, system, and non-transitory computer-readable storage medium for controlling an eye tracking system to optimize eye tracking performance under different lighting conditions, by obtaining a first image captured using a camera associated with the eye tracking system, the first image comprising at least part of an iris and at least part of a pupil of an eye illuminated by an illuminator associated with the eye tracking system at a current power of illumination selected from a set of predetermined power levels; determining a contrast value between an the iris and the pupil in the image; and, if the contrast value deviates less than a preset deviation threshold value from a preset minimum contrast value, setting the current power of illumination of the illuminator to the other predetermined power level in the set of predetermined power levels.