Investigating the association between eye colour and the Neurological Pupil index.

INTRODUCTION: Brown or dark brown eyes make it difficult to distinguish the contrast between a black pupil and the surrounding iris, which may result in clinical assessment errors. The pupillometer can be used to derive an indexed value, the Neurological Pupil index™ (NPi) for pupillary light reflex. However, there are limited data associating the NPi and iris colour. We examine the NPi and eye colour association. METHODS: Data were pooled from the Establishing Normative Data for Pupillometer Assessments in Neuroscience Intensive Care (END-PANIC) Registry. The analysis includes 14,168 observations collected from 865 patients with neurological conditions who were admitted to the intensive care unit. Summary statistics and statistical models were developed to examine the association using Statistical Analysis Software (SAS) summary procedure. RESULTS: The mean age of the cohort was 56 years (standard deviation = 17). Eye colour included dark brown (n = 339), blue (n = 234), brown (n = 173), green (n = 82), and other (n = 37). There was significant differences (p < 0.0001) between mean NPi values by eye colour [blue = 4.08 (0.92), brown = 3.34 (1.45), dark = 3.71 (1.33), green = 4.08 (0.67), other = 3.76 (1.25)]. However, a further random-effects mixed model after controlling for confounding variables revealed no significant difference in NPi values among different eye colour groups. CONCLUSIONS: The pupillary light reflex, when assessed using the pupillometer, is not dependent on the eye colour. Practitioners are not required to consider eye colour as a confounder when they perform pupillary assessment for examining patients with neurological conditions.

Impact of Increased Intracranial Pressure on Pupillometry: A Replication Study.

In a diverse, multicenter population, to confirm or refute the conclusions that pupillary light reflex changes are associated with increased intracranial pressure. DESIGN: Replication study. PATIENTS: Within the Establishing Normative Data for Pupillometer Assessments in Neuroscience Intensive Care registry there were 273 patients (16,221 pupillary observations) that included both intracranial pressure and pupillometry values. MEASUREMENTS AND MAIN RESULTS: To evaluate findings by the previous author, we explored for differences among measures of the pulmonary light reflex obtained from automated pupillometry with ICP values dichotomized as < 15 mm Hg (normal) versus ≥ 15 mm Hg (elevated). Analysis of t-test indicates statistically significant differences for all right and left mean pupilometer values, except right latency (p = 0.3000) and repeated measure mixed model (p = 0.0001). In the setting of increased intracranial pressure, mean pupilometer values were lower for both left and right eyes comparing to normal intracranial pressure, except right neurologic pupil index (3.98, 3.92;p = 0.0300) and left latency (0.27, 0.25; p < 0.0001). CONCLUSIONS: Our findings confirm and extend those of McNett et al Worsening measures of the pupillary light reflex using automated pupillometry are associated with elevated intracranial pressure.