Visual discomfort is caused by various factors when watching stereoscopic 3D contents. In particular, brightness change
is known as one of the major factors related to visual discomfort. However, most previous research about visual
discomfort dealt with binocular disparity as related to accommodation and vergence linkage. In this paper, we analyze
visual discomfort caused by brightness change using eye-movements and a subjective test. Eye-movements are
computed using eye pupil motion as detected from a near-infrared eye image. We measure eye-blinking and pupil size
while watching stereoscopic 3D videos with global and local brightness variations. The results show that viewers felt
more visual discomfort in local change than in global change of brightness in a scene.