In Horner's syndrome sympathetic nerve fibers have a defect, therefore the pupil of the involved eye will not dilate in darkness. Anisocoria which is worsened (greater asymmetry between the pupils) in the dark suggests the small pupil (which should dilate in dark conditions) is the abnormal pupil and suggests Horner's syndrome or mechanical anisocoria.
Ĭauses of anisocoria range from benign (normal) to life-threatening conditions.Ĭlinically, it is important to establish whether anisocoria is more apparent in dim or bright light to clarify if the larger pupil or smaller pupil is the abnormal one. Alkaloids present in plants of the genera Brugmansia and Datura, such as scopolamine, may also induce anisocoria. Some examples of pharmacological agents which may affect the pupils include pilocarpine, cocaine, tropicamide, MDMA, dextromethorphan, and ergolines. Pharmacological agents with anticholinergic or sympathomimetic properties will cause anisocoria, particularly if instilled in one eye.In ischemic lesions of the oculomotor nerve, pupillary function is usually spared whereas in compressive lesions the pupil is involved. Oculomotor nerve palsy: Ischemia, intracranial aneurysm, demyelinating diseases (e.g., multiple sclerosis), head trauma, and brain tumors are the most common causes of oculomotor nerve palsy in adults.Tonic pupil is characterized by delayed dilation of iris especially after near stimulus, segmental iris constriction, and sensitivity of pupil to a weak solution of pilocarpine. It may be associated with loss of deep tendon reflex (Adie's syndrome).
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