Noncomitant

Noncomitant is an adjective used in ophthalmology and neurology to describe a pattern of ocular misalignment (strabismus) in which the angle of deviation changes with the direction of gaze. It contrasts with comitant strabismus, in which the misalignment is approximately the same in all gaze positions.

Clinically, noncomitant deviations may produce diplopia that shifts as the patient looks left, right, up, or down. The motility exam reveals restriction or overaction of particular extraocular muscles, and prism cover testing shows different required prism powers depending on gaze direction.

Common causes include cranial nerve palsies (oculomotor, trochlear, or abducens), restrictive or infiltrative processes such as thyroid eye disease or orbital trauma, congenital motility anomalies, myasthenia gravis, and inflammatory conditions. Less often, mechanical problems of the orbital contents or nerve compression may produce noncomitant deviations.

Diagnosis relies on a comprehensive eye movement examination in primary and diagnostic positions, forced duction testing to distinguish paresis from restriction, and neuroimaging as indicated. Additional tests may be pursued when neuromuscular disorders are suspected—for example, serology for myasthenia gravis or nerve conduction studies.

Management focuses on treating the underlying cause and reducing diplopia. Options include prisms or occlusion for diplopia, vision therapy in appropriate cases, and surgical adjustment of extraocular muscles in selected incomitant strabismus. Prognosis varies with etiology and severity; some conditions stabilize or improve with treatment, while others require ongoing management.

See also: strabismus, comitant strabismus, diplopia, ocular motility disorders.