Automated Pupillometry May Replace Pharmacological Testing in Horner Syndrome

Macro shot of woman eyeball with small pupil. Close up of female eye ball
Investigators evaluate the diagnostic accuracy of pupillometry to discriminate between Horner syndrome and physiological anisocoria.

The following article is a part of conference coverage from the 2021 meeting of the North American Neuro-Ophthalmology Society, being held virtually from February 20 to 23, 2021. The team at Ophthalmology Advisor will be reporting on the latest news and research conducted by these leading experts in neuro-ophthalmology. Check back for more from the NANOS 2021 Meeting.


The use of automated pupillometry may replace time-consuming pharmacological testing as a methodology to differentiate Horner syndrome from physiological anisocoria. This is according to research1 presented at the North American Neuro-Ophthalmology Society (NANOS) 2021 Annual Meeting, held virtually February 20 to 23, 2021. 

Building on previous research results,2 investigators for the current study sought to evaluate the diagnostic accuracy of pupillometry to discriminate between Horner syndrome and physiological anisocoria. Currently, pharmacological testing with apraclonidine is the current gold standard for this condition. 

The study cohort included 31 adult patients who were referred for evaluation of anisocoria. All patients underwent automated binocular pupillometry under standardized light conditions both before and after apraclonidine 1% eyedrops. ROC curves were calculated through comparison of different cut-off values to apraclonidine testing results. Investigators defined a positive apraclonidine test as enlargement of the affected pupil and constriction of the nonaffected pupil within 3 to 4 seconds of lights off. 

In patients with a positive apraclonidine test result, change in anisocoria at 3 to 4 seconds relative to baseline was “significantly larger” compared with patients with a negative test result (P <.0079). 

ROC was calculated to determine the best cut-off valuate for anisocoria change. Utilization of a dilation lag at 3 to 4 seconds as a diagnostic criterion, with a 0.35 mm change cut-off, had a 94% sensitivity and 73% specificity for Horner syndrome diagnosis compared with the gold standard pharmacological testing. 

“Our data indicate that automated pupillometry on its own is a helpful and sensitive diagnostic test for differentiating the physiological anisocoria from sympathetic pupillary dysfunction,” the research says. “It may reduce the need for unnecessary further diagnostic steps such as pharmacological testing and [magnetic resonance] imaging.” 

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  1. Disse LR, Bockisch CJ, Weber KP, Fierz FC. Differentiation of Horner syndrome from physiological anisocoria using automated pupillometry compared with to apraclonidine testing. Presented at: North American Neuro-Ophthalmology Society (NANOS) 2021 Annual Meeting; February 20-23, 2021; Poster 132.
  2. Omary R, Bockisch CJ, Landau K, Kardon RH, Weber KP. Buzzing sympathetic nerves: A new test to enhance anisocoria in Horner’s syndrome. Front Neurol. 2019;10:107. doi:10.3389/fneur.2019.00107.