In Dr. Irving's lab, we are involved in on-going cross-sectional and longitudinal studies examining the developmental changes in saccades in young children, looking specifically at the saccadic amplitude- velocity relation. We have also been examining the effects of strabismus surgery on saccades. We are comparing the pre- and immediate post-operative main sequence data of patients undergoing strabismus surgery to better understand velocity control of saccadic eye movements in strabismus. We have also looked at changes in saccade dynamics and saccade conjugacy during a six week post-operative follow-up period. Disconjugate adaptation was found to occur. We plan to continue in this vein by examining the ability of the vestibulo-ocular reflex (VOR) to adapt monocularly.
In a current study we are looking at the development of the eye movement system and the relationship between adaptation and development within this system for children aged 3 through 15. The following questions are asked: Do environmental adaptations permanently affect the development of eye movements? What effect does the developmental stage have on a person's ability to alter their eye movement patterns? In this particular experiment, we are looking at the development of a type of eye movement called a saccade; the rapid eye movement which we use when looking from one object to another. We are studying the effect of age on the speed at which this type of eye movement can be made. We are also interested in the effects of age on the relationship between saccades, other types of eye movements, and head movements.
Measurements of eye movements are made using a video system, the El-Mar Eye Tracker. A head set containing a pair of miniature TV cameras is worn. The position of the centre of the pupil and the reflection of the first Purkinje image are used to determine eye position.
The Eye Tracker samples at 120 Hz and can be used for studying all kinds of eye movements including horizontal and vertical saccades. A magnetic sensor attached to the head set is used to measure head movement. No part of the instrument touches the eye. Since it is non-invasive, accurate, and easy to use, it's more practical for use in children compared with other devices available.