Elyse Lemery


PURPOSE. It has previously been shown that when contrast is increased monocularly,vertical vergence capabilities suffer. This effect has been demonstrated using a sine wave grating as the stimulus configuration. Similarly, we have presently measured vertical vergence response while using an anaglyphic field containing lines of random text. The deterioration of vergence facility with mismatched contrast is being compared between these two stimuli. This study measured the tolerance of vertical vergence control to mismatched contrast. The amount of contrast difference between the two eyes that caused a deterioration in vergence amplitude with a text stimulus was compared with previous data collected when using a sine wave grating.
METHOD. A full field anaglyphic target was projected onto a flat white surface at a distance of 1 meter. The target consisted of text with a line spacing of 1cpd. The subject wore anaglyphic glasses so that contrast could be varied for the right and left eyes independently. One of the subject's eyes was fixed at a contrast of 0.125 while the other eye's contrast was varied. Vertical disparity was added slowly and the maximum vergence response was measured with a modified nonius technique.

RESULTS. Normal subjects show best vergence response
when left and right eye contrasts were within a factor of 1.4.

CONCLUSIONS. The peak of the vergence amplitude shifts toward a similar contrast match to the eye with the fixed contrast. The tolerance for disparity change and maintaining fusion while viewing text seems to encompass a larger range of contrast difference than previously measured with a sine wave grating.


Year: 2001

Program Number: Poster 44

Author Affiliation: University of Houston

Co-Authors: Scott Stevenson, William Miller

Co-Author Affiliation: University of Houston, University of Houston

Room: Exhibit Hall C