Repeatability of Objective Pupil Function Measurement Among Collegiate Athletes

Abstract

Purpose : The diagnostic and prognostic importance of pupil findings in severe traumatic brain injury is well established. Objective pupillometry has been proposed as a potential screening tool for mild traumatic brain injury/concussion. The purpose of this study was to evaluate the repeatability of objective pupillometry in collegiate athletes performed by non-ophthalmic personnel.

Methods : A total of 186 collegiate athletes across eight sports consented to participate. Pupil function testing was done indoors in similar lighting conditions after an athlete’s training session by a single member of the Auburn University medical staff. Each measure was repeated twice per eye. All measurements were done with the Neuroptics NPi 200 infrared pupilometer. During measurement a short duration light is flashed and a three second video of the pupil is captured. Eight measures of pupil function are generated including: maximum and minimum size, maximum constriction velocity, average constriction velocity, percent constriction, constriction latency, dilation velocity and a proprietary index value the NPi. Intraclass correlation coefficients(ICC) were generated for each measure. Within subject root mean square error from general linear equations was used to develop smallest real differences(±1.96X √2 X Std dev) for each test parameter.

Results : Intraclass correlation coefficients (ICC) were good to excellent for all parameters with the exception of latency, which was poor at 0.27 and 0.28 OD and OS respectively. Mean differences between the first and second measures (bias) was minimal for all measures, the largest being +1.4% for Right eye percent constriction. Bias was minimal for the Left eye percent constriction at +0.08%. Smallest real differences were widest for the velocity measures constriction velocity (OD ±1.05, OS ±0.94) and maximum constriction velocity (OD ±1.36, OS ±1.24). Dilation velocity showed narrower smallest real differences at (OD ±0.58, OS ±0.47). Despite poor ICC smallest real differences were extremely narrow for latency measures(OD±0.06,OS± 0.07).

Conclusions : Non-ophthalmic medical staff are able to generate reproducible pupil function measures using the Neuroptics NPi200 pupilllometer. The utility of the device in concussion management warrants further study.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.