Objective: To detect time threshold of visual acuity. Methods: The optotypes are programmed in pascal. The size, the program and the lasting time of the optotypes are controlled by a computer. The subject looked at an optotype on the distant of 5 m. The time threshold of visual acuity is detected with the staircase method. Results: Time threshold of visual acuity in normal young men whose visual acuity are 1.0 is about 28.10msec, that in normal young men whose visual acuity are 1.2 is about 27.90msec, and that in normal young men whose visua...