Garzia R P, Nicholson S B
School of Optometry, University of Missouri-St. Louis.
Am J Optom Physiol Opt. 1988 Jan;65(1):61-3. doi: 10.1097/00006324-198801000-00016.
An anomalous horizontal forced-vergence fixation disparity curve in the shape of the letters V or U is presented. This phenomenon is associated with an increase in eso fixation disparity with base-out prism. This response is shown to be related to instructional set. Intrusion of voluntary vergence is suggested as the most likely basis for this effect.