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Dennis Jenkins, Yue Shi, Sean Pitetta, Ken Marion, Alex Ho, Srinivas R Sadda, Philip Le, Vikas Chopra; Reproducibility in Identifying Schwalbe’s Line on new High Definition Angle scans using Spectral Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2085.
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© ARVO (1962-2015); The Authors (2016-present)
OCT-based anterior chamber metrics such as angle opening distance are important in quantitatively evaluating the anterior chamber. For spectral domain optical coherence tomography (SDOCT) scans, these metrics are dependent on correctly identifying landmarks such as Schwalbe’s Line (SL).This study assesses the inter-grader reproducibility of identifying SL on the new High Definition (HD) Angle anterior segment SDOCT scan, which uses oversampling and enhanced depth imaging.
90 eyes of 45 participants were imaged in this IRB approved, prospective research study. Both normal and primary open angle glaucoma eyes were included as long as they had an open angle allowing for SL detection. HD Angle scans were captured using the Zeiss Cirrus 5000 (v9.5) (Carl Zeiss Meditec Inc. Dublin, CA). Two certified Doheny Image Reading Center evaluators analyzed the images in a masked, independent fashion.Each evaluator annotated the location of SL on each dewarped image using ImageJ v1.48 software (NIH, Bethesda, MD). The point selected as SL was captured as XY coordinates given by ImageJ, based on a scan width and height of 6233.7 µm and 4019.4 µm respectively. The Euclidean distance was calculated between the SL coordinates from each evaluator. Intraclass correlation coefficients (ICC) were calculated for both X and Y coordinates using IBM SPSS Statistics for Windows, v.19 (IBM Corp., Armonk, NY).
Mean difference of SL placement between evaluators was 76.88 ± 92.63µm (0 - 411.26µm). Exact concordance of SL placement between evaluators occurred in 5 scans. The mean XY coordinates for evaluator 1 and evaluator 2 were (3030.29, 2096.76) µm and (3027.73, 2089.80) µm respectively, with a mean absolute difference of (X= 50.20 and Y= 56.02) µm. The ICC for X-coordinates was 0.99 (0.993 - 0.997) and Y-coordinates was 0.98 (0.976 - 0.989) (p <0.001 and p <0.001).
This study is the first to quantify reproducibility of SL location identification using the Zeiss HD Angle OCT scan. Inter-grader reproducibility is excellent. The results contextualize precision of quantitative SDOCT anterior chamber metrics that rely on SL. Additionally, these findings establish a human benchmark for automated SL identification algorithms, which are needed to expand the set of anterior chamber measurement tools available to clinicians.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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