Listing's law

[lĭstĭngz]
n.
  1. The principle that when the eye turns from looking at one object and fixes upon another, it revolves about an axis perpendicular to a plane cutting both the former and the present lines of vision.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.