Infrared Video Pupillography Coupled with Smart Phone LED for Measurement of Pupillary Light Reflex

Abstract

Clinical assessment of pupil appearance and pupillary light reflex (PLR) may inform us the integrity of the autonomic nervous system (ANS). Current clinical pupil assessment is limited to qualitative examination, and relies on clinical judgment. Infrared (IR) video pupillography combined with image processing software offer the possibility of recording quantitative parameters. In this study we describe an IR video pupillography set-up intended for human and animal testing. As part of the validation, resting pupil diameter was measured in human subjects using the NeurOptics™ (Irvine, CA, USA) pupillometer, to compare against that measured by our IR video pupillography set–up, and PLR was assessed in guinea pigs. The set-up consisted of a smart phone with a light emitting diode (LED) strobe light (0.2 s light ON, 5 s light OFF cycles) as the stimulus and an IR camera to record pupil kinetics. The consensual response was recorded, and the video recording was processed using a custom MATLAB program. The parameters assessed were resting pupil diameter (D1), constriction velocity (CV), percentage constriction ratio, re-dilation velocity (DV) and percentage re-dilation ratio. We report that the IR video pupillography set-up provided comparable results as the NeurOptics™ pupillometer in human subjects, and was able to detect larger resting pupil size in juvenile male guinea pigs compared to juvenile female guinea pigs. At juvenile age, male guinea pigs also had stronger pupil kinetics for both pupil constriction and dilation. Furthermore, our IR video pupillography set-up was able to detect an age-specific increase in pupil diameter (female guinea pigs only) and reduction in CV (male and female guinea pigs) as animals developed from juvenile (3 months) to adult age (7 months). This technique demonstrated accurate and quantitative assessment of pupil parameters, and may provide the foundation for further development of an integrated system useful for clinical applications.

Static and dynamic pupillometry data of healthy individuals

“…Kasthurirangan and Glasser studied the dynamic accommodative and pupillary responses to step stimuli in 66 human subjects (ages: 14–45 years) and demonstrated that the mean peak velocity of pupil constriction decreases significantly with age. The pupillary dynamics were also studied in guinea pigs, using a protocol that allows quantitative evaluation of the constriction and re‐dilation response over time . It was found that the constriction and re‐dilation velocity significantly decrease in adult guinea pigs compared with juvenile ones .…”

“…The pupillary dynamics were also studied in guinea pigs, using a protocol that allows quantitative evaluation of the constriction and re‐dilation response over time . It was found that the constriction and re‐dilation velocity significantly decrease in adult guinea pigs compared with juvenile ones . On the other hand, Bremner has investigated the correlations between the amplitude and peak velocity of constriction in the PLR of normal subjects to determine the effects of stimulus intensity, pupil size and age on this relationship.…”

<p>A Review of Advancements and Evidence Gaps in Diabetic Retinopathy Screening Models</p>

“… 54 Another study reported that reduced pupillary dilatation amplitude was detected in hyperglycemic patients with DR, 55 which may assist in patient diagnosis and stratification by severity. Smartphone LEDs have been used as stimuli in combination with infrared video pupillometry, 56 and now entirely iPhone-based pupillometry can provide similar results to infrared pupillometry. 57 Further studies are required to determine the relative accuracy, costs, and ease of these pupillary light response tests, or a combination thereof, for sensitivity and specificity for diagnosing DR and determining its severity.…”

Quantitative Pupillometry in the Intensive Care Unit

“…Preliminary studies have shown comparable results between these smartphone applications and traditional infrared pupillometry. 28,29…”