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Assessing the Reproducibility of Quantitative In Vivo Confocal Microscopy of Corneal Nerves in Different Corneal Locations

Kim, Gene MD; Singleton, J. Robinson MD; Mifflin, Mark D. MD; Digre, Kathleen B. MD; Porzio, Michael T. BS; Smith, A. Gordon MD

doi: 10.1097/ICO.0b013e31829dd7f8
Clinical Science

Purpose: To evaluate the reproducibility of in vivo confocal microscopy for quantitative corneal nerve analysis in different corneal locations.

Methods: Corneal confocal microscopy was performed on 10 healthy participants, and the corneal nerve fiber length, corneal nerve fiber density, corneal nerve branch density, and tortuosity coefficient were measured at 5 predetermined locations for only the right eye. Bland–Altman plots, intraclass correlation coefficient (ICC), and coefficient of variation of all 4 corneal nerve measurements were compared between 2 visits and between readers to assess reproducibility. Two technicians performed a masked analysis of images from both visits.

Results: Ten participants with a mean age of 31.3 ± 2.8 years were imaged at 2 different time points separated by a mean of 4.3 ± 4.3 weeks. The interobserver agreements were better than the intervisit agreements for all the 4 corneal nerve measurements as evaluated using Bland–Altman plots. The intervisit ICC ranged from 0.13 to 0.45, and the interobserver ICC ranged from 0.55 to 0.94. The differences between observers and the differences between sessions were not statistically different among all the 5 locations (P > 0.1) for each corneal nerve measurement.

Conclusions: Single confocal images have poor reliability for any of the 4 corneal nerve measurements, and there is no single location on the cornea that has improved reproducibility. Averaging 5 images, from different locations, improves the reproducibility and is essential for obtaining clinically meaningful data.

*John A. Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah Health Care, Salt Lake City, UT;

Ruiz Department of Ophthalmology and Visual Science, The University of Texas Medical School at Houston, Houston, TX;

Robert Cizik Eye Clinic, Houston, TX; and

§Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT.

Reprints: A. Gordon Smith, Department of Neurology, University of Utah School of Medicine, 30 North 1900 East, SOM3R242, Salt Lake City, UT 84132 (e-mail:

Supported by The Research to Prevent Blindness Foundation (G.K., M.D.M.), NIHR01DK064814 (A.G.S, J.R.S, M.T.P.), ADA08-CR52 (A.G.S., J.R.S., M.T.P.), a Challenge Grant to The University of Texas Medical School at Houston from Research to Prevent Blindness (G.K.), National Eye Institute Vision Core Grant P30EY010608 (G.K.), and the Hermann Eye Fund (G.K.).

The authors have no conflicts of interest to disclose.

Received March 04, 2013

Accepted May 24, 2013

Copyright © 2013 Wolters Kluwer Health, Inc. All rights reserved.