Photo Quiz

An Asymmetrical Pupil


Am Fam Physician. 2019 Feb 1;99(3):191-192.

A 73-year-old woman presented with asymmetrical pupils. She had no loss of vision, double vision, eye pain, light sensitivity, or abnormal sweating. The patient had a history of bilateral cataract surgery, repair of right retinal detachment, and repair of the right orbital bone after a traumatic event. She had a 30-pack-year history of smoking. Although the patient had several medical conditions, none involved the eye or use of ophthalmic medications.

On physical examination, the external eyelids were normal in appearance with no findings of ptosis. The sclerae were clear bilaterally, with an approximately 1-mm difference in pupillary size observed in light and darkness (Figure 1). Pupils were round and reactive to light. Cranial nerves were intact with no abnormality noted on confrontation of visual fields.

Recent lung cancer screening with low-dose computed tomography revealed multiple lung nodules; however, none were in the apical region. Additionally, magnetic resonance imaging with and without contrast media was obtained during a prior emergency department visit as part of a stroke workup. It showed chronic microvascular ischemic disease with no evidence of a mass.

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Based on the patient's history and physical examination findings, which one of the following is the most likely diagnosis?

  • A. Horner syndrome.

  • B. Physiologic anisocoria.

  • C. Third nerve palsy.

  • D. Traumatic mydriasis.


The answer is B: physiologic anisocoria. Physiologic anisocoria is the most common etiology of uneven pupil size, occurring in approximately 20% to 24% of the U.S. population. It is a benign condition, and no treatment is required.13

The diagnosis of physiologic anisocoria is clinical, based on history and physical examination findings. Reviewing old photos or driver's licenses of the patient can assist in establishing the diagnosis because physiologic anisocoria is a persistent and long-standing condition.3,4 The anisocoria is usually equal in light and darkness.3

Horner syndrome presents as the classic triad of unilateral miosis, ptosis, and anhidrosis.5 The anisocoria

Address correspondence to Omici N. Uwagbai, MD, MPH, at Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.

The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the U.S. Army Medical Department, the U.S. Army Service at large, or the Department of Veterans Affairs.


show all references

1. Steck RP, Kong M, McCray KL, Quan V, Davey PG. Physiologic anisocoria under various lighting conditions. Clin Ophthalmol. 2018;12:86–89....

2. Lam BL, Thompson HS, Corbett JJ. The prevalence of simple anisocoria. Am J Ophthalmol. 1987;104(1):69–73.

3. Gross JR, McClelland CM, Lee MS. An approach to anisocoria. Curr Opin Ophthalmol. 2016;27(6):486–492.

4. Kedar S, Biousse V, Newman NJ. Approach to the patient with anisocoria. July 29, 2017. UpToDate. (subscription required). Accessed December 3, 2018.

5. James B, Bron A. Lecture Notes: Ophthalmology. 11th ed. West Sussex, UK: Wiley-Blackwell; 2011.

6. Kruger JM, Lessell S, Cestari DM. Neuro-imaging: a review for the general ophthalmologist. Semin Ophthalmol. 2012;27(5–6):192–196.

This series is coordinated by John E. Delzell Jr., MD, MSPH, Associate Medical Editor.

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