Modern Pupillometer Demonstrates High Agreement With Older Model

Pupillometer: Instrument For Measuring The Distance Between Pupils For Proper Lens Prescription. (Photo By BSIP/UIG Via Getty Images)
Inter-device agreement was consistent in both individuals with neurological disease and healthy control participants.

Data obtained using 2 different generations of pupillometers have a high level of agreement, and are translatable between both devices, according to a study published in the Journal of Clinical Neuroscience. The data showed agreement whether performing measurements on healthy controls or patients with neurological disease. 

Researchers enrolled 70 participants (mean age, 62.8±16.5 years, 55% women) consisting of 20 individuals at risk for cerebral edema and 50 controls in the study. They performed a series of measurements obtained using the NPi®-200 (NeurOptics) and the NPi®-300 (NeurOptics) devices including neurologic pupil index (NPi), latency, maximum pupil diameter (maxPD), minimum pupil diameter (minPD), constriction velocity (CV), and dilation velocity (DV). The investigators obtained data from the NPi-200 first and repeated measurements with the NPi-300 within 5 minutes. They measured participants in the control group only once for a total of 50 samples per device and measured participants in the cerebral edema risk group multiple times for a total of 121 samples per device (mean sample, 6.05±1.98).

The researchers noted a high level of agreement between the 2 devices with respect to NPi (k=0.95; CI, 0.91-0.99) and pupil diameter assessment (k=0.91; CI, 0.87-0.96). Percentage agreement was greater than 80% for all measurements, with agreement greater than 95% in latency, minPD, percent change in pupil diameter, CV, and DV. Agreement was consistent among both healthy controls and patients with neurological disease. 

“Readings from the NPi-200 and NPi-300 are remarkably similar and provide several new insights that may inform clinical practice and future research,” according to the investigators. “Not all physiologic measures have high instrument reliability.”

Study limitations include a small sample of patients with cerebral edema risk and a rapid succession of measurements which may not have allowed the patients’ pupils to fully recover.


Stutzman S, Iype P, Marshall J, et al. Inter-device reliability of the NPi-200 and NPi-300 pupillometers. J Clin Neurosci. 2022;100:180-183. doi:10.1016/j.jocn.2022.04.023