In order to measure the degree of ocular fatigue and general fatigue among the workers using visual display terminal (VDT), pupillary dynamics were measured with open-loop light stimulation for 26 subjects of a mean age of 25.9 years. VDT loads were TV games for 30 min under indirect light of 100 lux. The eight parameters of pupillary light reflex with open-loop pupillometer were examined before and after VDT loads. On the right eyes, two parameters and one value increased 9.2% (Student's t-test: P less than 0.005, max.), 25.7% (Student's t-test: P less than 0.005, Min.) and 14.8% (Student's t-test: P less than 0.005, min/max) just after the load and then gradually decreased and returned to the pre-load level after a 10 to 15-min rest period. Two parameters increased 11.7% (Student's t-test: P less than 0.05, 1/2C) and 12.9% (Student's t-test: P less than 0.05, VD), one parameter decreased -9.0% (Student's t-test: P less than 0.05, 0.63D) and three parameters were constant (Student's t-test: L, A and VC) just after the load. On the left eyes, the same tendencies were observed. But there were no significant differences (Student's t-test) between the right and left eyes. The change pattern of the eight parameters were small in degree and similar to the changes when the sympathetic nervous system was activated.