An 80-year-old man with a history of bilateral cataract surgery 15 years ago and mild nonproliferative diabetic retinopathy (NPDR) was referred for evaluation of abnormal pupils. He has not had an ophthalmic examination in approximately 15 years and reports no new visual symptoms. Visual acuity measures 20/25 OU. Pupillary examination is significant for bilateral small, irregular pupils that constrict minimally to bright light. However, both pupils constrict briskly and symmetrically during accommodation to a near target. Extraocular movements are full, with no evidence of ptosis or limitation of upgaze. Dilated fundus examination demonstrates mild NPDR OU without macular edema or other acute posterior segment abnormalities.
Which of the following is the most appropriate next step in the diagnostic evaluation?
A. Obtain serologic testing for syphilis
B. Perform dilute pilocarpine testing
C. Attribute the pupillary findings to prior cataract surgery and recommend routine follow-up
D. Obtain emergent MRI of the brain and orbits
E. Perform apraclonidine testing
Correct answer: A.
This patient exhibits light-near dissociation, characterized by small, irregular pupils that respond poorly to light but constrict normally to a near target. This pattern is characteristic of Argyll Robertson pupils, which are classically associated with neurosyphilis.
When Argyll Robertson pupils are suspected, the diagnostic evaluation should include serologic testing for syphilis. Recommended testing includes a nontreponemal test, such as rapid plasma reagin (RPR) or venereal disease research laboratory (VDRL), followed by confirmatory treponemal testing, such as fluorescent treponemal antibody absorption (FTA-ABS) or Treponema pallidum particle agglutination (TPPA).
B. Dilute pilocarpine testing is used to evaluate suspected Adie tonic pupil. Adie pupils are typically larger and demonstrate a slow, tonic near response, in contrast to the brisk near constriction observed in this patient.
C. Although prior cataract surgery can result in pupillary abnormalities, it would not typically produce light-near dissociation. It should not be assumed to explain the findings without further evaluation.
D. Urgent magnetic resonance imaging (MRI) of the brain and orbits is not indicated as an initial test in a stable patient who lacks additional findings suggestive of an acute structural lesion.
E. Apraclonidine testing is used to evaluate suspected Horner syndrome, which typically presents with miosis, ptosis, and dilation lag.
References:
American Academy of Ophthalmology EyeWiki. Argyll Robertson Pupils. Updated April 14, 2026.
Cleveland Clinic Health Library. Argyll Robertson Pupils. Updated February 25, 2024.
Dichter SL, Khan Suheb MZ, Shubert GS. Argyll Robertson Pupil. [Updated 2024 Jan 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537179/
By: Cristian Flores