To develop methods for the objective measurement of ocular fatigue.

Fifteen patients were enrolled in the present study. Subjects performed visual tasks on a computer for one hour. A survey of ocular fatigue was conducted with a questionnaire. Tear break-up time, blinking rate, ocular protection index, conjunctival injection, maximal blinking interval, temperature of the ocular surface, and visual evoked potential were evaluated before and immediately after the task. Surface electromyography of the orbicularis oculi muscle was performed before and during the task.

The survey showed increases in subjective ocular fatigue in all subjects. Tear break-up time, ocular protection index and maximal blinking interval decreased, while temperature of the ocular surface increased after the task. Conjunctival injection showed a tendency to increase. Electromyography, and visual evoked potential did not change significantly.

In the present study, tear break-up time, ocular protection index, maximal blinking interval, and temperature of the ocular surface changed as ocular fatigue increased. Therefore, these measures can be objectively used for the evaluation of ocular fatigue.