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Updated: May 5, 2026

Objective Nociceptive Assessment in Ventilated ICU Patients: A Feasibility Study Using Pupillometry and the Nociceptive Flexion Reflex
Published on: July 4, 2018
Time to maximum pupil constriction is variable in neurocritical care patients
Abdulkadir Kamal1, Emerson B Nairon2, Anna Bashmakov2
1Department of Nursing, University of Texas Southwestern Medical Center, Dallas, TX, USA.
The time to maximum constriction (tMC) in the pupillary light reflex (PLR) varies significantly between neuroscience intensive care unit (NSICU) patients. This variability must be considered in clinical assessments of pupil health.
Area of Science:
- Neuroscience
- Ophthalmology
- Critical Care Medicine
Background:
- Quantitative pupillometry (QP) is increasingly utilized for assessing the pupillary light reflex (PLR).
- The pupillary light reflex provides objective measures of neurological function.
- Understanding variations in PLR components like time to maximum constriction (tMC) is crucial for clinical interpretation.
Purpose of the Study:
- To investigate the uniformity of time to maximum constriction (tMC) in neuroscience intensive care unit (NSICU) patients.
- To determine the variability of tMC within and between individuals in an NSICU population.
Main Methods:
- Cross-sectional study of 50 NSICU patients with normal PLR.
- Standard of care pupil assessments were used to collect tMC data.
- Data analyzed for within-subject (left vs. right eye) and between-subject variability.
Main Results:
- The mean tMC was 0.97 (0.17) seconds, normally distributed across patients.
- No significant difference in mean tMC between left (0.98s) and right (0.96s) pupils.
- Substantial within-subject (mean difference 0.13s) and between-subject (range 0.46s-1.35s) variability in tMC was observed.
Conclusions:
- Time to maximum constriction (tMC) is not a fixed value and exhibits significant variability in NSICU patients.
- Clinical applications assessing pupil health should account for this tMC variability.
- Further research is needed to correlate tMC variations with specific clinical outcomes.
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