O1014: Differences in Pupillary Light Reflex Metrics After Concussion Persist at Clinical Recovery

Background: Pupillary light reflex (PLR) metrics have been demonstrated to differ in adolescents with concussion from healthy controls, with concussed individuals manifesting enhancement of those metrics. What is currently not known is whether or not these PLR metrics in concussed adolescents return back to the range of metrics observed in healthy controls when the concussed adolescents appear clinically recovered from their concussion. Our objective in this study is determine the potential utility of PLR metrics as physiological biomarker for concussion recovery.

Methods: Prospective cohort of adolescents between ages 12 and 19 years with pupillary light reflex (PLR) assessment conducted between August 1st, 2017 and May 11th, 2021, recruited from a specialty concussion program and private suburban high school. The study cohort included healthy adolescents (n = 203) and adolescents with a diagnosis of concussion (n=106) who were determined to be clinically recovered at their final visit for clinical care. The distribution of demographic and clinical characteristics for adolescents recovered from concussion were compared with healthy controls using χ2 statistics for categorical variables (sex, race/ethnicity, and history of prior concussion) and F tests for age. The means of the PLR metrics were compared among adolescents with concussion and controls with 1-way analysis of variance using F tests. We accounted for multiplicity by calculating Bonferroni corrections for the 9 PLR metrics; we present the 99.44% CIs around the mean values and the mean differences between comparison groups.

Results: 6 of 9 metrics continued to be significantly greater among concussed cases after Bonferroni correction (minimum pupil diameter: 2.96 mm vs 2.66 mm; difference, 0.31; 99.4% CI, 0.17-0.44; percentage constriction: 37.84% vs 32.91%; difference, 4.93; 99.4% CI, 2.98-6.88; average constriction velocity: 3.09 mm/s vs 2.50 mm/s; difference, 0.59; 99.4% CI, 0.38-0.79; average dilation velocity, 1.34 mm/s vs 1.24 mm/s; difference, 0.11; 99.4% CI, 0.01-0.20; peak dilation velocity: 1.86 mm/s vs 1.66 mm/s; difference, 0.20; 99.4% CI, 0.08-0.31; and T75: 1.73 seconds vs 1.46 seconds; difference, 0.27; 0.10-0.44) compared to healthy adolescents.

Conclusion: These findings suggest that enhancement of PLR metrics in concussed adolescents may persist after concussion and may not return to normal at the time of clinical recovery which may have implications for return to risk activities such as contact or collision sports.