Objective: Using a custom-developed segmentation algorithm, agreement of corneal epithelial thickness profile measurements between two spectral domain optical coherence tomography (SD-OCT) systems was assessed.
Methods: Eighteen left eyes (18 subjects; mean±standard deviation; age, 23.2±0.9 years) were imaged twice on nonconsecutive days by a custom-built ultra-high resolution OCT (UHR-OCT) system and a commercial RTVue OCT system. A segmentation algorithm based on axial gradient information and a shortest path search was developed to measure corneal epithelial thickness profiles from the SD-OCT images.
Results: There was good correlation between the automated and manual segmentation positions of the epithelium. The epithelial thickness differences between automated and manual segmentations by the UHR-OCT and RTVue OCT systems were 0.4±0.3 μm and 1.1±0.5 μm, respectively. The intraclass correlation coefficients (ICCs) and coefficients of repeatability for repeated UHR-OCT measurements of epithelial thickness were 0.90±0.05 μm and 1.44±0.01 μm, respectively. For RTVue OCT, the ICCs and coefficients of repeatability were 0.88±0.04 μm and 2.16±0.01 μm, respectively. The epithelial thickness measured by RTVue OCT was 1.1±0.2 μm greater than that by UHR-OCT (P<0.05, paired t test), and ICC for the agreement between the 2 systems was 0.85±0.06. The average 95% limit of agreement was −1.67 to 3.79 μm.
Conclusions: For images of different qualities from both SD-OCT systems, the custom-developed automated segmentation of the corneal epithelium had good repeatability for thickness profile measurements. The accurate and precise algorithm also demonstrated good agreement of epithelial thickness profile measurements between the two SD-OCT systems.
School of Ophthalmology and Optometry (M.S., Z.X., C.Y., L.L., J.L., Q.C., F.L.), Wenzhou Medical University, Wenzhou, China; and Department of Ophthalmology (J.W.), Bascom Palmer Eye Institute, University of Miami, Miami, FL.
Address correspondence to Fan Lu, M.D., O.D., School of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325027, China; e-mail: firstname.lastname@example.org
M. Shen and Z. Xu have equally contributed to the project. Design of the study (M.S., Z.X., J.W., F.L.); Conduct of the study, data collection, analysis, and interpretation (M.S., Z.X., C.Y., L.L., J.L., Q.C., J.W., F.L.).
Supported by research grants from Zhejiang Provincial Natural Science Foundation of China (Y13H180030 and LQ12H12002), Zhejiang Medical Technology and Education of China (2013KYA132 to Shen), National Nature Science Foundation of China (Grant No. 81170869 to Lu), and the Wenzhou Science and Technology Program (Y20110058 and Y20110103).
The authors have no conflicts of interest to disclose.
The Research Review Board of Wenzhou Medical University approved this study.
Accepted December 16, 2013