Prism distortion and accommodative change

The literature concerning oculomotor changes during adaptation to prism distortion has dealt mainly with the question of eye movements. The present study examined accommodation during exposure to distortion by ophthalmic prisms. Ss were asked to fixate four targets of equal visual angle at four distances. Accommodation was measured at each distance by means of a Laser-Badal optometer. Repeated measures for the same target distances were obtained prior to during and after exposure to binocular prisms. The results indicated that prisms induce underaccommodation at each of the target distances, although the total range of predistortion and distortion accommodation was restricted. Significant recovery from the effects of induced underaccommodation was observed at near target distances. No significant aftereffects of wearing the prisms was observed. In a second experiment, where target background contrast was increased, consistent underaccommodation was again observed and recover was observed at the near target distance. The range of accommodative change was also considerably improved. It was concluded that the angular magnification of ophthalmic prisms induced underaccommodation. It was suggested that partial recovery from the prism effect may be related to alterations in vergence.