Chaotic analysis of focal accommodation system and pupil area during VDT work

Evaluation of stress during a VDT task is important when designing proper human-computer interactions. The purpose of this research is to show that stress during VDT tasks can be evaluated using chaotic features such as the fractal dimension and the first Lyapunov exponent for the focal accommodation system and the pupil area. As for step control measurement and fixed target measurement, the fractal dimension tends to decrease over time. This shows that the fractal dimension for the focal accommodation system and the pupil area can be used to evaluate stress during VDT tasks. The first Lyapunov exponent took positive values. Not only the fractal dimension but also the first Lyapunov exponent in the fixed target measurement was larger than those in the linear control and step control measurements. The chaotic property in the fixed target measurement was higher than that in the linear control and step control measurements. However, the first Lyapunov exponent hardly changed over time for all three accommodation measurements