Consequences of Traumatic Brain Injury for Human Vergence Dynamics

Purpose: Traumatic brain injury involving loss of consciousness has focal effects in the

human brainstem, suggesting that it may have particular consequences for eye movement

control. This hypothesis was investigated by measurements of vergence eye movement

parameters.

Methods: Disparity vergence eye movements were measured for a population of 123 normally

sighted individuals, 26 of whom had suffered diffuse traumatic brain injury (dTBI) in

the past, while the remainder served as controls. Vergence tracking responses were measured

to sinusoidal disparity modulation of a random-dot field. Disparity vergence step

responses were characterized in terms of their dynamic parameters separately for the

convergence and divergence directions.

Results: The control group showed notable differences between convergence and divergence

dynamics. The dTBI group showed significantly abnormal vergence behavior on

many of the dynamic parameters.

Conclusion:The results support the hypothesis that occult injury to the oculomotor control

system is a common residual outcome of dTBI.