Swinging Flashlight versus Virtual Reality-Swinging Flashlight Detection of Reactive Afferent Pupil Defect

Abstract

Purpose : The swinging flashlight test (SFT) is a critical part of the ophthalmologic exam to detect relative afferent pupillary defect (RAPD). However, it often misses afferent pupillary defects due to poor execution and subjective qualitative interpretation. The purpose of this study is to test SFT versus a novel virtual reality swinging flashlight test (VR-SFT) in detecting RAPD in routine eye exams.

Methods : A total of 69 participants consented to participate in the study following the guidelines of the University of Texas Medical Branch’s review board for working with human subjects. Subjects were analyzed for RAPD by certified ophthalmic staff and tested with the Zuckkoli Afferent Pupillary Device (“ZAP” ™) VR headset for eye tracking. The test comprised of four protocols, each tailored with multiple illumination sequences and durations, demonstrating flexibility and adaptability to virtual reality constraints. The study involved manipulating luminance levels to simulate the effects of neutral density filters and adjusting target size to mitigate accommodative responses. A RAPD score was calculated using a linear relationship between the pupillary contraction amplitude/pupil diameter and the difference of light amount for each eye. RAPD scores outside of -0.3 and 0.3 were considered positive for RAPD.

Results : Patients recruited for the study were predominantly women (66.67%), Caucasian (75%), and had a mean age of 50.59 years (SD = 17.5). SFT detected RAPD in 2 subjects and the VR-SFT detected RAPD in 9 subjects out of the 69 who received routine screening. Both systems detected RAPD in 2 of the subjects. These RAPD-positive subjects had history of ocular pathologies and average RAPD scores as follows: empty sella syndrome with a score of 0.30 (OD), macular scar with a score of -0.31 (OS), branch retinal artery occlusion with a score of 0.38 (OD), and open angle glaucoma with a score of -1.65 (OS). Further investigation indicated the subject with open angle glaucoma had progressive nerve fiber layer thinning contributing to RAPD.

Conclusions : The “ZAP” ™ VR system reliably detected RAPD and was more sensitive in detecting RAPD compared to SFT. The VR-SFT provided an objective RAPD score grading the severity of the RAPD, thus may be used in the future for managing disease progression. However, studies with ocular pathologies in larger numbers need to be done for further validation.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.