Additional usage possibilities for the computerized Hess screen

摘要

The purpose of the study was to work out a method how to use the computerized Hess screen in proximal vergence measurements. Proximal vergence or vergence due to knowledge of nearness is one of four independent components making up the total vergence response. Proximal vergence is expressed as a ratio - proximal convergence/test distance (PC/T). The computerized Hess screen is usually used to detect and to measure an ocular misalignment in patients with paralytic strabismus in different directions of gaze. The computerized Hess screen can be used to assess PC/T ratio in different directions of gaze, providing the open-loop disparity vergence and accommodation systems and assuming that tonic vergence is stable. The fusional system loop is opened using red/green filter goggles, objects with different size and color, a completely darkened room, and vertical dissociation (using a prism). The accommodation system loop is opened using pinhole. The test was performed on 16 neurologically and binocularly normal subjects (14 women, 2 men; average 24 y., 20-38 y.). Average PC/T ratio in a primary position for the whole group was 2.8 pd/D with a standard deviation +-0.8 pd/D, which correlates with results in literature obtained by other methods.