Portable pupillography of the swinging flashlight test to detect afferent pupillary defects

Objectives To investigate the ability of a portable, personal computer-driv en, pupillometer to record the pupillary response curve during the swinging flashlight test. Also, to determine whether these response curves can be u sed to identify and quantify relative asymmetry in the pupillary light refl ex between eyes in healthy volunteers with simulated afferent pupil defects (APDs) and patients with optic neuropathies. Designs Comparative, observational case series and instrument validation. Participants: Healthy volunteers with no known ocular disease and patients (n = 20) with various optic neuropathies noted to have relative APDs on exa mination. Methods: Pupillary response curves of the right eye were recorded with a po rtable, electronic, infrared pupillometer from healthy volunteers (with and without simulated APDs) and patients with APDs while the light stimulus al ternated between eyes, simulating the swinging flashlight test. Simulated A PDs in healthy volunteers were created with increasingly dense neutral dens ity filters in front of the left eye. Main Outcome Measures: Differences in constriction amplitude, latency, and constriction velocity of the pupillary response with right eye stimulation versus left eye stimulation in both groups of subjects. Results: A significant correlation between neutral density filter strength and intereye differences was seen for all measurement parameters in volunte ers with simulated APDs. Depending on the measurement parameter and stimulu s intensity, simulated APDs of 0.6 log units or more could be distinguished from normal responses. Clinically graded true APDs had intereye difference s similar to simulated APDs of the same density. Those with real and simula ted APDs of 0.9 log units or more could be distinguished from healthy volun teers with 80% sensitivity and 92% specificity. Responses from those with r eal and simulated small APDs of 0.3 to 0.6 log units could not be distingui shed reliably. Conclusions: Portable, personal-computer driven, electronic, infrared pupil lography can record the swinging flashlight test accurately and identify la rge afferent pupillary defects. An affordable, portable, reliable device fo r identifying relative APDs would be useful in the identification and follo w-up of patients with neurogenic vision loss. Ophthalmology 2000;107:1913-1 922 (C) 2000 by the American Academy of Ophthalmology.