Eye movements in the absence of binocular vision

Dr Helen Griffiths, Lecturer in Orthoptics
Dr David Buckley, Lecturer
Dr Jon Whittle, Clinical Research Associate

The mechanism of suppression in strabismus is unclear and contribution of the suppressing eye to the generation of eye movements has received little attention. Our studies are designed to determine how the strabismic eye contributes to saccade generation in the presence of suppression and abnormal retinal correspondence.

Eye movements are measured using the Skalar IRIS 6500 infrared limbal tracker and stimuli are presented to each eye separately using four liquid crystal polymer shutters to dissociate the eyes.

Graph

Saccadic eye movement recordings using the Skalar IRIS 6500 infrared limbal tracker, a) subject with normal BSV, b) subject with exotropia, c) subject with esotropia.

Experiments with distractors presented to the fixing eye, strabismic eye or both eyes have been used to investigate saccadic eye movements in the absence of binocular vision. The results have shown that although distractors in the strabismic eye were not perceived, they did affect the saccade response in terms of latency and accuracy.

The influence of the central fixation target in the strabismic eye on saccade generation by inducing disconjugate saccade adaptation has also been investigated. The findings were that in the presence of suppression, disconjugate adaptation similar to that in normal BSV was possible.

This research suggests that information from the suppressed eye is available to the saccadic system by either a sub-cortical pathway or processed cortically without conscious awareness.

References

Griffiths HJ. (2003). Saccades in the absence of binocular vision. PhD Thesis, University of Sheffield

Griffiths HJ, Buckley D, Whittle JP. (2003). Rapid monocular adaptation of saccade amplitude in constant strabismus. Transactions of the 28th European Strabismological Association Meeting, Bergen, Norway, de Faber (ed.) Taylor & Francis, New York, pp45-49.