A SEE-THROUGH BINOCULAR SYNCHRONOUS PUPILOMETER FOR NON-INVASIVE AUTONOMIC NERVOUS SYSTEM ASSESSMENT

Abstract

Pupillary dynamics provide valuable physiological information for evaluating autonomic nervous system activity because pupil constriction and dilation are directly modulated by parasympathetic and sympathetic pathways. However, many conventional pupillometry systems are limited by monocular acquisition, visual-field occlusion, insufficient binocular synchronization, and limited adaptability across subjects, which may compromise the reliability of bilateral pupillary assessment. This study presents a see-through binocular synchronous pupilometer for non-invasive measurement of pupillary light reflex responses. The proposed system integrates a beam-splitter-based optical configuration, infrared illumination, dual CCD cameras, microprocessor-based hardware triggering, and an adjustable helmet-mounted structure. The see-through configuration allows subjects to maintain natural fixation while enabling infrared pupil imaging, whereas the hardware-triggered architecture ensures synchronized bilateral acquisition. A preliminary validation experiment was conducted on 20 healthy volunteers, with three repeated trials per subject under controlled illumination. The system achieved a binocular temporal deviation of less than 1/60 s and a synchronization accuracy greater than 98%. Quantitative analysis showed stable bilateral pupil measurements, with baseline pupil diameters of 5.82±0.41 mm and 5.79±0.39 mm for the left and right eyes, respectively. The RMS inter-eye asymmetry was 0.12±0.05 mm, while the intra-subject repeatability error was 0.08±0.03 mm. The pupil detection success rate reached 97.5%, and the valid frame ratio after blink correction was 96.2%. These results demonstrate that the proposed pupilometer provides reliable, repeatable, and synchronized binocular pupillary measurements under controlled experimental conditions. Although the present study was limited to healthy subjects, the system offers a promising technical platform for future autonomic nervous system assessment and clinical validation in populations with diabetic autonomic neuropathy or other autonomic disorders.