Author(s) :

Hemant Selvamurugan.

Volume/Issue :

Abstract :

The pupillary light reflex (PLR) is a rapid, involuntary constriction of the pupil in response to light and is increasingly recognized as an objective marker of brainstem and autonomic function. Clinical pupillometers can quantify the PLR but are expensive and largely confined to medical settings, limiting access in the school and community sports environments where rapid neurological screening could be most valuable. This study evaluated whether key features of the PLR can be quantified using only consumer video equipment. Ten healthy participants (ages 15–35 years) were each tested three times, for a total of 30 trials. The pupillary response to a white light-emitting diode (LED) stimulus was recorded with a smartphone camera at a fixed distance, and pupil diameter was measured manually, in pixels, across extracted video frames. From these measurements, baseline diameter, minimum diameter, constriction magnitude, percent constriction, and time to minimum diameter were calculated. Baseline pupil diameter ranged from 138 to 161 pixels and minimum diameter from 112 to 122 pixels. Pupil constriction averaged 32.9 pixels, and the mean time to minimum diameter was approximately 0.55 seconds (range 0.4–0.7 seconds), with low within-subject variability (coefficients of variation ≤ 1.7%). Baseline diameter was positively associated with absolute constriction magnitude, and constriction scaled with initial pupil size rather than converging to a fixed minimum. These results show that core PLR features can be measured consistently in this small healthy sample and under the specific device and conditions used, without specialized clinical equipment. They provide preliminary, setup-specific descriptive values and support the feasibility of further developing and validating accessible, videobased PLR measurement, such as a portable sideline concussion scanner.