Quantifying pupillary asymmetry through objective binocular pupillometry in the normal and mild traumatic brain injury (mTBI) populations.

INTRODUCTION: Little is known about human inter-ocular pupillary asymmetry (IOPA). Thus, the purpose of the present investigation was to assess objectively static and dynamic IOPA in normals and in individuals with mild traumatic brain injury (mTBI).
METHODS: The pupillary light reflex (PLR) was assessed in an adult population of normals and in those with mTBI using the Neuroptics DP-2000 binocular pupillometer. Four stimulus conditions were used to optimize the assessment. Two aspects of the pupil were assessed: baseline diameter prior to light stimulation and the dynamic amplitude of constriction following light stimulation.
RESULTS: There was no statistical difference in either the static or dynamic IOPA between the two groups. Thus, the data were combined for a better global parameter estimate. The mean average static IOPA was 0.26 mm (SD = ± 0.20 mm) or 4.17% (± 3.29%). The mean average dynamic IOPA was dependent on the light stimulus condition, with the average across all four test conditions being 0.11 mm (± 0.10 mm) or 1.84% (± 1.70%). DISCUSSION: The inter-ocular pupillary effects of mTBI appear to be symmetrical rather than asymmetrical in nature. The findings provide clinicians and researchers a useful quantitative guideline to assess normal vs abnormal static and dynamic inter-ocular pupillary asymmetry (IOPA) in these two populations.