We read with interest the article by Hofeldt et al1 in the December 1996 issue of the Archives. Their study highlights the importance of binocular vision for hitting a baseball. In addition, the authors define a new criterion for ocular dominance in relation to the effect of a 0.6 optical density filter on hitting performance. Finally, the authors compare the Pulfrich phenomenon with the motion-in-depth channel. Although we agree that the motion-in-depth channel (or motion stereoscopic vision) is likely an important factor in a player's ability to successfully hit a baseball, we do not believe that the Pulfrich phenomenon is the appropriate manner by which to demonstrate this.
The authors have equated the motion-in-depth channel with the Pulfrich phenomenon. These 2 binocular phenomena are different in physiologic basis and in the manner tested. To perceive the Pulfrich effect, the subject must fixate on a static target while a ball
Laby DM, Kirschen DG, Zagelbaum B. Motion Stereoscopic Vision, the Pulfrich Phenomenon, and Baseball Hitting. Arch Ophthalmol. 1997;115(8):1084. doi:10.1001/archopht.1997.01100160254024