Cranial Nerves III, IV, and VI: Oculomotor Function.

Motor activity affecting the direction of gaze, the position of the eyelids, and the size of the pupils are served by cranial nerves III, IV, and VI. Unusual oculomotor activity is often encountered in psychiatric patients and can be quite informative. Evaluation techniques include casual observation and simple tests that require no equipment in addition to the sophisticated methods used in specialty clinics and research labs. This article reviews pupil size, extraocular movements, nystagmus, lid retraction, lid lag, and ptosis. Beyond screening for diseases and localizing lesions, these tests yield useful information about the individual's higher cortical function, extrapyramidal motor functioning, and toxic/pharmacologic state.