JAMA Ophthalmology, November 2020
Master et al. investigated the utility of pupillary light reflex (PLR) data as potential physiological biomarkers for concussion in teen athletes and found that nearly all PLR metrics examined were much higher in those who sustained concussion than in healthy controls.
For this study, the researchers recruited athletes from a concussion program and a private suburban high school. All told, 98 athletes with a diagnosis of sport-related concussion (SRC) and 134 healthy controls participated. Participants were 12 to 18 years old, and 56% and 58% of the SRC and control groups were male, respectively. In the SRC group, PLR values were obtained at a median of 12 days following injury (interquartile range, 5-18 days). Main outcomes were the differences in PLR measurements between the study groups, including maximum and minimum pupillary diameter, peak and average constriction/dilation velocity, percentage of constriction, latency, and time to 75% pupillary redilation (T75).
Eight of the nine metrics examined were found to be significantly greater in the SRC group after Bonferroni correction, as follows: maximum pupil diameter (4.83 mm vs. 4.01 mm); minimum pupil diameter (2.96 mm vs. 2.63 mm); constriction percentage (38.23% vs. 33.66%); average constriction velocity (3.08 mm/s vs. 2.50 mm/s); peak constriction velocity (4.88 mm/s vs. 3.91 mm/s); average dilation velocity (1.32 mm/s vs. 1.22 mm/s); peak dilation velocity (1.83 mm/s vs. 1.64 mm/s); and T75 (1.81 seconds vs. 1.51 seconds).
The only metric that did not differ substantially was latency, defined as the time to maximum constriction in response to the light stimulus. Exploratory analyses showed that girls with SRC had longer T75 than their male counterparts (1.96 seconds vs. 1.63 seconds). In healthy controls, some PLR metrics diminished after exercise, including pupil size, and there were no gender-related differences for any metric in this group.
The findings suggest that elevated PLR metrics may be physiologic biomarkers of acute concussion in teenagers. To better understand the utility of these metrics, the authors encourage multicenter studies, as well as multivariable modeling, to account for factors such as history of concussion. They also recommend more research on PLR metrics in girls, following exercise, and longitudinally after concussion. (Also see related commentary by Wesley T. Beaulieu, PhD, and Adam R. Glassman, MS, in the same issue.)
The original article can be found here.