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Published on: January 29, 2020
Inter- and intraobserver reliability of pupil diameter measurement during 24 hours using the Colvard pupillometer
Michael K Yoon1, Gregory Schmidt, Thomas Lietman
1Department of Ophthalmology, Francis I. Proctor Foundation, University of California San Francisco, San Francisco, Calif 94143, USA.
Purpose:
To evaluate the inter- and intraobserver agreement of pupil size diameter measurements determined using the Colvard pupillometer.
Methods:
The eyes of 69 patients were examined (T1) using the Colvard pupillometer under mesopic and scotopic conditions by two examiners and repeated 1 hour (T2) and 24 hours (T3) later. The limits of agreement (mean difference between measurements +/- 2 standard deviations) were calculated for measurements between examiners (inter-examiner agreement) and between different time points measured by the same examiner (intra-examiner agreement).
Results:
At T1, there was a 99% and a 97% chance of two different examiners producing readings within 0.5 mm under mesopic and scotopic conditions, respectively. There was a 15% chance and a 9% chance of finding a pupil difference > 0.5 mm over 1 hour under mesopic and scotopic conditions, respectively. For mesopic and scotopic measurements taken 24 hours apart, there was a 31% chance and a 21% chance, respectively, of finding a difference > 0.5 mm by the same examiner.
Conclusions:
This study showed high interobserver agreement under scotopic conditions, with 98% of measurements between two examiners falling within 0.5 mm, but substantial variability in pupil diameter measurements over 24 hours. These results suggest that serial office measurements may be necessary to establish the true range of pupil size.
