Introduction
Pupil size and reactivity have been studied in the adult and pediatric populations in an attempt to objectively quantify pain. Previously conducted studies have demonstrated pupillometry as a promising biomarker for objective pain measurement.1-3 A 2012 study demonstrated the significant correlation between patient verbally reported pain and pupillary dynamics in order to guide narcotic administration.2 Another study showed that pupillometry is a more sensitive test for pain assessment and response to medication than other hemodynamic markers, including vital signs.3 Factors including patient age, sex, and ethnicity have been previously studied in order to better understand the potential variables affecting pupil dynamics and establish a set of normal values. Regarding pupillary dynamics in younger patients, Brown et al. evaluated the pediatric population and demonstrated a slight change in pupil dynamics across pediatric age groups as well as differences across various ethnicities.1
Pupillometry is conducted using a hand-held device that measures a variety of pupil dynamics following exposure to an infrared light stimulus. The parameters of pupil constriction and dilation velocity as well as minimum and maximum pupil sizes are the most significant categories used for comparison of patient populations. The testing is noninvasive, quick, and carries little to no risk for the patient, making pupillometry an ideal tool for pain measurement.
The clinical application of pupillometry is particularly useful in the young pediatric population as it is more difficult to understand subjective patient-reported pain, and an objective pain evaluation measurement is needed. For example, in the pediatric sickle cell disease population, vaso-occlusive crisis is a common complication that presents with acute pain. Vaso-occlusive pain crises are often over or undertreated due to fear of medication side-effects, possible addiction, and variable tolerance.4 Quantifying acute pain and response to treatment has been difficult due to dependence on subjective measures. In this study, we aim to measure pupillometry measurements in pediatric patients with sickle cell disease as a first step to establish normative data for future utilization in cases of acute pediatric vaso-occlusive pain crisis.1