Using a hand-held pupillometer to quantify pupil constriction as part of the accommodation reflex

Quantitative pupillometry (QP) provides a reliable measure of the pupillary light reflex. The pupil accommodation reflex (P-AR) occurs when there is a change in visual focus from near to far or from far to near. The ability to measure the P-AR using handheld QP has not been described. We aimed to explore whether QP can objectively detect changes in pupil diameter associated with differences in gaze fixation distance.

This prospective study enrolled 100 healthy adult volunteers. Bilateral QP measurements were obtained with each observation lasting 16 s (s) for both near and far focused gazes. Time-series plots were generated from the spreadsheet-based measurements, using the series of readings from each eye, and were subsequently uploaded for use in multiple data-analysis models.

From 200 paired bilateral observations, 178 provided reliable pupil measurements that differed during the far-focus, near-focus, far focus observation. Pupil diameter decreased significantly from far to near fixation (t = 11.52; P < 0.0001) and increased significantly when returning to far fixation (t = -9.73; P < 0.0001). Across all 200 observations, minimum and maximum pupil diameters differed significantly, confirming the presence of the miosis occurring as a component of the near triad response to gaze fixation. No significant difference was observed between eyes.

These novel findings establish QP as an objective method for quantifying the P-AR. This provides a potential tool for evaluating autonomic function, brain arousal, and neurophysiological integrity.