The use of video refraction to measure the dynamic properties of the near triad in observers of a 3-D display.

Objective: Recording of the dynamic behaviour of the near triad during viewing of a three-dimensional (3-D) display is attempted. This may then be used to identify the possible origin of asthenopia and other ocular problems which occur whilst viewing such displays.

Methods: Subjects viewed a 3-D display through an image splitter. Video recordings of ocular responses (pupil diameter, vergence and accommodation) were made with a commercially available video refraction unit at a distance of 1.2 m from the subject. Continuous recordings were made whilst a step-wise disparity of up to 2.6 degrees was introduced between the targets presented to the two eyes, but the accommodative stimulus remained unchanged. Image analysis from the recordings was carried out on a personal computer.

Results: Results showed various complex patterns of response, with the accommodation and vergence recorded reflecting the effect of stimulus conflict. Difficulty in fusional convergence was recorded when disparity was large, and the recordings reflected the subjects' comments.

Conclusion: The video refraction method is a useful tool for studying the dynamic behaviour of the near triad.