To the Editor.
—In their recent paper on eye movement abnormalities in amyotrophic lateral sclerosis (Archives 1982;39:684-686), Leveille et al referred to our earlier publication on the subject.1 They stated that we relied primarily on closely spaced, sequential light-bulb flashes for inducing pursuits—a target that might itself induce saccades. That statement is inaccurate. We used two stimuli to induce pursuits. One was a dot of projected light that moved at controlled speeds (analog electronics); the other was a series of sequentially flashing light bulbs that created the illusion of a single dot of light in motion (digital electronics). We reliably recorded defective as well as normal pursuits using both stimuli. The digital stimulus was used because we found it to be better than the analog in maintaining attention in fatigued, distractable, or debilitated patients. It is indeed possible that sequential light flashes may induce saccades rather than smooth pursuits
Jacobs L, Bozian D, Heffner RR, Barron SA. Eye Movements in Amyotrophic Lateral Sclerosis. Arch Neurol. 1983;40(7):460. doi:10.1001/archneur.1983.04050070090033
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