BASIC INVESTIGATION Repeatability of Measuring Corneal Nerve Migration Rate in Individuals With and Without Diabetes Khaled Al Rashah, MSc (Optom),* Nicola Pritchard, PhD,* Cirous Dehghani, PhD,* Alfredo Ruggeri, PhD,† Pedro Guimaraes, MSc,† Christopher Poole, PhD,* Anthony Russell, MBBS, PhD,‡§ Rayaz Malik, MD, PhD,¶k Nathan Efron, PhD, DSc,* and Katie Edwards, PhD* Purpose: To assess the repeatability of measuring the corneal nerve migration rate in individuals with and without neuropathy. Methods: Wide-field montages of the subbasal corneal nerve plexus were generated at baseline and after 3 weeks for 14 participants. Montages were manually examined side by side to identify a referent landmark in the inferior whorl region (origin) and throughout each montage. A software program was developed to measure nerve migration of all identified points relative to the origin. Repeatability was determined by measurement of nerve migration for within observer (one researcher on 2 occasions, 5 days apart) and between observers (2 observers) within 4 different zones based on the distance from the origin and in the vertical section of the wide- field montage. The impact of images being montaged with fully automated software on repeatability was also investigated. Results: The mean difference between observations 1 and 2 for observer 1 was 0.02 6 1.3 mm/wk (P = 0.94), with an intraclass correlation coefficient (ICC) of 0.99 [95% confidence interval (CI) = 0.99–1.00], and the mean difference between observer 1 and 2 was 0.3 6 1.2 mm/wk (P = 0.41), with an ICC of 0.99 (95% CI = 0.99– 1.00). The mean difference between observations 1 (images montaged by semiautomated software) and 2 (images montaged by fully automated software) was 1.2 6 4.9 mm/wk (P = 0.41), with an ICC of 0.96 (95% CI = 0.87–1.00). Conclusions: Measuring corneal nerve migration rate is highly repeatable for within and between observers and when using different methods of image montaging. Key Words: repeatability, cornea, nerves, migration rate (Cornea 2016;35:1355–1361) C orneal confocal microscopy (CCM) is a noninvasive technique that enables evaluation of the cornea in vivo at the cellular level. 1,2 It has been used to detect corneal nerve fiber loss in several ophthalmic conditions 3–6 and several systemic diseases such as diabetic peripheral neuropathy (DPN). 1,2,7–11 The early diagnosis and detection of DPN is crucial to monitor patient deterioration and evaluate new therapies. Current techniques for evaluating nerve morphology, such as nerve and skin biopsies, allow a detailed pathological assessment; however, both methods are invasive and painful, cannot be implemented in routine practice, and do not allow for repeated measurements of an individual nerve. Over the past decade, the quantification of corneal nerve parameters using in vivo CCM has been investigated as a novel marker for the diagnosis of DPN. This technique shows promise as a diagnostic marker of DPN and is gaining more widespread use. CCM offers a distinct advantage over nerve biopsies in that it can be performed in a short time frame and repeatedly in the same location, allowing observation and measurement of nerve migration. This advan- tage is not yet exploited in current studies. 8,12–17 We have recently published a technique to measure corneal nerve migration and highlighted its potential clinical utility for assessing DPN. 18 Although CCM has been shown to have high repeatability in evaluating the morphology of static corneal nerve fibers, 17 the repeatability of measuring corneal nerve migration rate within and between observers has not been reported. Therefore, we have undertaken a study to determine the within- and between-observer repeatability of a semiauto- mated technique for measuring corneal nerve migration rate. MATERIALS AND METHODS Sample Size The sample size used for this study was estimated assuming a preferred test–retest difference of less than 10% of the clinically relevant nerve migration rate (5 mm/wk). Analysis using G*Power 3.1 software showed that 11 participants were required to achieve an effect size of 0.5 mm/wk with 70% confidence. 19 Participants Images used in this analysis were obtained from 14 participants, including 4 healthy individuals, 5 neuropathy-free individuals with diabetes, and 5 individuals with diabetic neuropathy. Participants had no history of contact lens wear, Received for publication March 7, 2016; revision received April 20, 2016; accepted April 20, 2016. Published online ahead of print June 16, 2016. From the *Institute of Health and Biomedical Innovation, Queensland University of Technology, Queensland, Australia; †Department of Infor- mation Engineering, University of Padova, Padova, Italy; ‡Department of Diabetes and Endocrinology, Princess Alexandra Hospital, Brisbane, Australia; §School of Medicine, University of Queensland, Brisbane, Australia; ¶Center for Endocrinology and Diabetes, Institute of Human Development, University of Manchester, Manchester, United Kingdom; and kWeill Cornell Medicine-Qatar, Doha, Qatar. The authors have no funding or conflicts of interest to disclose. Reprints: Katie Edwards, PhD, Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Kelvin Grove, Queensland 4059, Australia (e-mail: katie.edwards@qut.edu.au). Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. Cornea  Volume 35, Number 10, October 2016 www.corneajrnl.com | 1355 Copyright Ó 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.