Exophoria at near in presbyopia.

The exophoria at near working distances through a plus lens addition which exists in presbyopia was investigated in order to explain the paradoxical lack of asthenopic symptoms associated with this condition. Fixation disparity measurements indicate that the exophoria which is measured by the von Graefe technique does not exist under binocular conditions. Further analysis indicates that presbyopes may have unrestrained use of accommodative convergence.