iPhone-based Pupillometry: A Novel Approach for Assessing the Pupillary Light Reflex

Abstract

Significance: The response of the pupil to a flash of light, the pupillary light reflex (PLR), is an important measure in optometry and in other fields of medicine that is typically evaluated by qualitative observation. Here we describe a simple, portable, iPhone-based pupillometer that quantifies the PLR in real time. Purpose: To describe a novel application to record the PLR and to compare its technical capabilities with a laboratory-based infrared (IR) camera system. Methods: Pupil sizes were measured from 15 visually-normal subjects (age: 19–65 years) using an IR camera system and the Sensitometer test. This test elicits pupillary constriction using the iPhone flash, records pupil size using the camera, and provides measurements in real-time. Simultaneous recordings were obtained with the Sensitometer test and IR camera and two measures were calculated: 1) dark-adapted steady-state pupil size; 2) minimum pupil size following the flash. The PLR was defined as the difference between these two measures. Pupil size was also recorded during the re-dilation phase following the flash. Bland-Altman analysis was used to assess the limits of agreement between the two methods. Results: Statistically significant correlations between the IR and Sensitometer test measures were found for the PLR (r = 0.91, P < 0.001) and re-dilation size (r = 0.65, P = 0.03). Bland-Altman analysis indicated a mean PLR difference of 6% between these two methods. The PLR limit of agreement was 14%, indicating that 95% of subjects are expected to have IR and Sensitometer test measurements that differ by 14% or less. Bland-Altman analysis indicated a mean re-dilation size difference of 1% between the two methods; the limit of agreement was 5%. Conclusions: There is excellent agreement between pupil responses recorded with the Sensitometer test and IR camera. The Sensitometer test provides a highly promising approach for simple, portable, inexpensive pupillary measurements.

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

“…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. Smartphone approaches are promising as they permit patients to detect DR themselves, without the need for ophthalmologists or optometrists, and instead, pupillary response recordings can be sent to an expert for interpretation.…”

Asthma and Allergy Mobile Apps in 2018

“…Associated with the KagenAir application is an iPhone-based mobile application that accurately measures smooth muscle speeds of contraction during the pupillary light reflex, the Sensitometer® test at Sensitometer.com [61, 62]. Studies are underway to determine if this mobile app can identify patients with hyperreactive airways (e.g., asthma) as pupillary smooth muscles reflect smooth muscles throughout the body and autonomic nervous system function [63].…”

Evaluation of two portable pupillometers to assess clinical utility

“…Assessment of the pupillary light reflex (PLR) following a suspected concussion injury is an essential component of the physical examination [ 1 ]. Within the past 30 years, portable pupillometers have become available that can analyze the PLR waveform [ 2–5 ]. These instruments are designed to measure latencies (ms), constriction velocities (const-vel, mm/s) and reflex amplitudes (RA, mm) from changes in the pupillary diameter (PD; mm) that follow a brief flash of visible light.…”

“…These instruments are designed to measure latencies (ms), constriction velocities (const-vel, mm/s) and reflex amplitudes (RA, mm) from changes in the pupillary diameter (PD; mm) that follow a brief flash of visible light. Many authors agree that these portable instruments provide objective measures from the light reflex with greater accuracy and prognostic value compared with the subjective assessments obtained using the traditional pen light examination [ 1 , 2 , 4 , 6 , 7 ]. As a result, portable pupillometers have been used to study the changes in pupil size and PLR after concussion [ 1 , 4 , 6 , 7 ].…”

“…Because portable infrared pupillometers are not widely available, several entrepreneurs have proposed that the smartphone can be adapted for use as a portable pupillometer [ 2 , 8 ]. Measuring the PLR with a smartphone would provide a low cost and convenient alternative to the more expensive infrared-based pupillometer.…”