Saccade-vergence properties remain more stable over short-time repetition under overlap than under gap task: a preliminary study

Abstract

Under natural circumstances, saccade-vergence eye movements are among the most frequently occurring. This study examines the properties of such movements focusing on short-term repetition effects. Are such movements robust over time or are they subject to tiredness? 12 healthy adults performed convergent and divergent combined eye movements either in a gap task (i.e., 200 ms between the end of the fixation stimulus and the beginning of the target stimulus) or in an overlap task (i.e., the peripheral target begins 200 ms before the end of the fixation stimulus). Latencies were shorter in the gap task than in the overlap task for both saccade and vergence components. Repetition had no effect on latency, which is a novel result. In both tasks, saccades were initiated later and executed faster (mean and peak velocities) than the vergence component. The mean and peak velocities of both components decreased over trials in the gap task but remained constant in the overlap task. This result is also novel and has some clinical implications. Another novel result concerns the accuracy of the saccade component that was better in the gap than in the overlap task. The accuracy also decreased over trials in the gap task but remained constant in the overlap task. The major result of this study is that under a controlled mode of initiation (overlap task) properties of combined eye movements are more stable than under automatic triggering (gap task). These results are discussed in terms of saccade-vergence interactions, convergence-divergence specificities and repetition versus adaptation protocols.

Benefits from Vergence Rehabilitation: Evidence for Improvement of Reading Saccades and Fixations

“…For all subjects 75–100% of convergence and divergence trials were used in the statistical analysis. To be precise, 11.6 ± 8% were rejected mostly due to blink and loss of signal, similarly for convergence and divergence, at the group level which is similar to the rejection level from a previous study of overlap vergence in healthy young adults (Lang et al, 2014 ).…”

Objective Evaluation of Vergence Disorders and a Research-Based Novel Method for Vergence Rehabilitation

“…These criteria of exclusion are standard. 38 , 39 , 42 Note that subject JA performed quasi-systematically a blink during the movements recorded after the Vd-s rehabilitation protocol (≥90% of divergence movements were concerned) and this behavior is known to diminish the dynamic performance of eye movements. 43 For the remaining subjects ( N = 18), 80 to 90% of the trials were used for the analysis; such rejection level (10 to 20%) is similar to that reported in a previous study of vergence in healthy young adults.…”

“… 43 For the remaining subjects ( N = 18), 80 to 90% of the trials were used for the analysis; such rejection level (10 to 20%) is similar to that reported in a previous study of vergence in healthy young adults. 38 , 39 …”

Effects of Pure Vergence Training on Initiation and Binocular Coordination of Saccades

“…These criteria used for marking vergence and saccades are standard and have been used in many other studies. 11,[28][29][30] To evaluate the quality of binocular coordination we measured the disconjugacy (see Fig. 3B), that is, the amplitude difference between the saccade of the right and the left eye (P À I); this criterion is standard also.…”