Pupil Unrest Index (PUI) is often used clinically for assessing exhaustion and sleepiness. Although pupil size measuring, which is based on the image processing of the eye, can be affected by blink, this influence has not been sufficiently considered for PUI evaluation. Hence, this paper seeks to examine the relationship between blink and indices of the pupil. The result shows that blink rate has a significant effect on the indices of the pupil. The difference in pupillary indices across experimental conditions was revealed by the appropriate estimation of pupil size during blink.