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Keke Liu, Florence Cabot, Yu-Cherng Chang, Marco Ruggeri, Sonia H Yoo, Jean-Marie A Parel, Fabrice Manns; Variability of Ciliary Muscle Segmentation in OCT Images. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2708. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Variability of manual segmentation of the ciliary muscle (CM) may prevent accurate CM thickness measurements from OCT images. This study aims to quantify intra- and inter-examiner variability of CM thickness and CM thickness change during accommodation measured from manually segmented OCT images.
A commercial SD-OCT system (Telesto II, Thorlabs, Newton, NJ) with imaging speed of 28,000 A-lines/s, axial resolution of 7.5 μm, axial range of 2.5 mm operating at a central wavelength of 1325 nm was coupled with a custom-made accommodation unit capable of providing monocular step stimuli. Three eyes from three subjects (24, 40, and 48 y.o.) were dynamically imaged in response to a step stimulus from 0 to 2 D. Two examiners manually segmented 20 OCT images from each imaging session, the first and last 10 images when the CM was relaxed and accommodated, respectively. Each image was segmented 10 times. CM thicknesses were calculated at the inner apex and 1.0 mm from the scleral spur (Figure 1) in each image. Relaxed and accommodated CM thicknesses were defined as the average thickness of the first 10 images and last 10 images, respectively. CM thickness change due to accommodation was defined as the difference in thickness between the accommodated and relaxed states. Intra-examiner variability was quantified for each subject as the 95% confidence interval of CM thickness and thickness change over 10 repetitions of CM segmentation. Inter-examiner variability was quantified as the mean difference in CM thickness and thickness change between the two examiners.
Intra-examiner variability was generally greater for measurements at the inner apex than measurements at a distance of 1.0 mm away from the scleral spur (Table 1). The mean inter-operator variability at the inner apex for relaxed CM thickness and CM thickness change was 50.5 and 25.0 μm, respectively (Table 1).
The variability of manual segmentation of the CM surfaces in OCT images may significantly affect the outcome of CM thickness measurements and should be considered when performing accommodation studies.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
CM OCT image. Red line: Upper boundary; Blue line: Lower boundary; White arrow: Inner apex; Teal and purple dashed lines: CM thickness at the inner apex and 1.0 mm from the scleral spur, respectively.
Mean change (µm) ± 95% confidence interval of relaxed CM thickness and CM thickness change at the inner apex and 1.0 mm from the scleral spur.
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