[Physiological ocular incongruity in man (author's transl)]

Ocular incongruity is not always symptomatic of pathology: it is sometimes simply found among the many physiological characteristics of man. The various situations which can bring about a physiological ocular incongruity are found successively during instrumental vestibular trials: incongruities in amplitude are recorded during the rapid phase of the provided nystagmus and incongruities in speed during the slow phase. These incongruities appear during the caloric responses for the homolateral eye to the irrigation and in the rotary, sinusoidal pendular test for the eye homolateral to the direction of the rapid phase of the provoked nystagmus. During a voluntary blink an ocular incongruity of direction appears as an intorsion of the two eyes. Incongruous ocular movements increase during sleep. They appear equally often during onset of sleep and during the stages comprising slow waves or paradoxical sleep. In children engaged in reading or submitted to an optokinetic test, congruity is not present at first but only occurs once the child has acquired the oculocephalic dissociation.