An Adult With Unilateral Mydriasis

Karima S. Khimani; Rod Foroozan, MD

Disclosures

October 04, 2017

Discussion

Tonic pupils were first reported at the turn of the 20th century and were described as tonically dilated and having a delayed reaction to convergence and accommodation.[4]

In 1931, the Australian neurologist William John Adie drew attention to what he explained as a benign disorder characterized by a combination of tonic pupils and absent deep tendon reflexes, a condition labeled as Adie syndrome.[4]

With convergence, the tonic pupil constricts slower and redilates more sluggishly than the fellow normal pupil. Patients with a tonic pupil typically present with photophobia and blurred vision with accommodation.[1] However, in many cases, the patient is asymptomatic when the anisocoria is noted.

The tonic pupil is postulated to be caused by damage to the postganglionic parasympathetic ciliary nerve fibers that innervate the eye.[1] The regeneration of axons occurs over a period of weeks, and the resulting inappropriate reinnervation of the musculature results in a poor response to light and accommodation. The damage to the nerve fibers often occurs in a segmental distribution, which can manifest as regional paralysis of the iris sphincter, best appreciated with slit lamp magnification. In addition, the denervation of the ciliary body results in an increase in the number of postsynaptic acetylcholine receptors, making the eye hypersensitive to dilute (0.125% or 0.0625%) pilocarpine. This feature of the tonic pupil is sometimes used as a diagnostic and therapeutic tool.[5] However, the tonic pupil is most commonly a benign condition and often requires no treatment.[1]

The tonic pupil typically occurs unilaterally and has a higher incidence in females by a factor of 2.6.[1] Although it is most commonly idiopathic, a tonic pupil, particularly when bilateral, may be associated with rheumatologic disorders and autoimmune conditions; and it may occur as a paraneoplastic syndrome, particularly with breast and lung malignancies, or may be seen in systemic dysautonomia, including Ross syndrome, which is also characterized by anhidrosis and areflexia.[1]

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