METHODOLOGICAL CAVEATS FOR MONITORING BINOCULAR EYE POSITION WITH NONIUS STIMULI

Three experiments, using two sets of Nonius lines placed in a random-d ot stereogram, indicated that Nonius alignment does not always reflect binocular eye position and, thus, a caveat is necessary when Nonius a lignment is used to monitor binocular eye position. We found that: (a) two Nonius lines with visual line values that differed by up to 7.6 m in of are can appear aligned; (b) the two lines of each of the two Non ius sets continued to appear aligned despite a change in vergence angl e of 5.9 min of are; and (c) the Nonius alignment reflected eye positi on better, when the binocular dots near the Nonius lines were eliminat ed. (C) 1998 Elsevier Science Ltd. All rights reserved.