Walsh & Hoyt: Ocular Alignment

When the eyes are not aligned on the same object, strabismus is present. The strabismus may be congenital or acquired and may be caused by central or peripheral dysfunction. In some individuals, particularly those with isolated congenital strabismus, the amount of ocular misalignment is unchanged regardless of the direction of gaze or of which eye is fixating the target. This type of strabismus is termed comitant or concomitant. On the other hand, when the amount of an ocular deviation changes in various directions of gaze, with either eye fixing, or both, the strabismus is said to be incomitant or noncomitant. Congenital comitant strabismus is occasionally associated with other neurologic dysfunction, and acquired comitant strabismus may rarely occur as a sign of intracranial disease. Most cases of acquired comitant strabismus appear in otherwise normal children and adults, as well as in persons with neurologic or systemic disease, from decompensation of a pre-existing phoria, or as a result of latent hypermetropia. Thus, most instances of neuropathic or myopathic strabismus are of the incomitant variety.