Lees screen

screen, Lees 

An instrument similar to the Hess screen. It consists of two internally illuminated screens placed at right angles. One eye views one screen directly, the other views the second screen via a mirror; hence, the eyes are dissociated. When one eye fixates a point on one illuminated screen, its position as seen by the second eye is indicated with a wand on the second, non-illuminated screen. When this is illuminated, the position of the wand relative to the screen markings indicates whether a muscle or set of muscles is paretic or not.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
Orthoptic assessment was Hess or lees screen test, Diplopia chart, 3-steps tests.
When used correctly, the Hess chart (or Lees screen) provides a major weapon in the armory for differential diagnosis of incomitant deviations).