Investigating the association between eye colour and the Neurological Pupil index

Sameer Al-Obaidi, Folefac Atem, Sonja E. Stutzman, Venkatesh Aiyagari, Dai Wai M. Olson

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)436-440
Number of pages5
JournalAustralian Critical Care
Issue number5
StatePublished - Sep 2020


  • Assessment
  • Cranial nerves
  • Critical care
  • Intracranial pressure
  • Monitoring
  • NPi
  • Oculomotor
  • Pupillary light reflex

ASJC Scopus subject areas

  • Emergency
  • Critical Care


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