Vision Problems – Eye Movement Disorders
There are three basic types of eye movements: fixations, saccades, and pursuits. Fixation is the act of maintaining visual attention on one point in space, Saccades are voluntary eye movements used to scan the environment, the type of eye movement used when reading, and Pursuits are eye movements used to track a moving target, the type of eye movement used when following traffic.
Eye movement disorders include basic deficiencies in fixations, saccades, or pursuits.
Fixation tremors can occur in a variety of conditions, including Parkinsonism. Fixation may be difficult for a child with ADHD. Nystagmus is a condition in which the eyes oscillate back and forth. In saccade accuracy, usually drifts, overshooting or undershooting can occur in isolation in the absence of other vision problems. This is one reason why it is crucial that every patient with reading difficulty have a thorough assessment of saccade function. Traditional eye examinations do little if anything to evaluate saccades, resulting in a false sense of security that everything is fine. Deficiencies in pursuits are more likely to occur in broad neurological or motor control problems such as cerebral palsy.