Effects of Exertion on PLR; A study of pupillary light reflex in rugby players before and after exercise

AimTo investigate the effects of physical exertion on pupillary light reflex (PLR) metrics in sports participants, with the aim of determining whether exercise-induced changes could potentially confound concussion assessment using PLR. Materials and methodsTwenty-five adult rugby players underwent PLR assessment, using the MindMirror smartphone application, before and after a 30-55 minute rugby practice session or game. PLR metrics included latency, maximum and minimum pupil diameters, maximum constriction velocity, and pupil size correlation. Paired t-tests were used to compare pre- and post-exertion PLR metrics. ResultsNo statistically significant differences were observed between pre- and post-exertion assessments in any of the measured PLR metrics (p > 0.05 for all metrics). The most notable, though still non-significant, change was in maximum constriction velocity (mean difference: 1.47 mm/s, p = 0.08 for pupil 1; 1.09 mm/s, p = 0.27 for pupil 2). ConclusionThis study suggests that PLR metrics, as measured by a smartphone-based pupillometer, do not appear to be affected by rugby-related exertion. These findings support the potential use of PLR assessment in concussion screening protocols without the need to account for exercise-induced changes. However, further research with larger sample sizes and in full-contact situations is needed to confirm these results and their applicability in concussion assessment. Plain language summaryPupil size and reactivity have been critical components of the clinical assessment of patients with head injury and concussion for decades. Pupillary examination may provide critical information related to new or worsening intracranial pathology, and quantitative PLR examination is increasingly used outside of the hospital setting, particularly for concussion assessment in sports medicine. Exertion-dependent changes could confound valid measurement, however, and compromise the detection of concussion, so we investigated PLR assessment with the MindMirror smartphone application. We found no systematic differences in PLR variables between exertion and non-exertion groups. Tweetable abstractA novel smartphone-based AI tool did not reveal exertion-related differences in pupillary light reflex measurement in rugby players.