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Kelvin Zhenghao Li, Kai Xiong Cheong, Louis Wei Yi Lim, Colin S Tan; A Novel and Faster Method of Manual Grading to Measure Mean Choroidal Thickness using Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1294.
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© ARVO (1962-2015); The Authors (2016-present)
Choroidal thickness (CT) measurements are typically obtained from manual segmentation of individual optical coherence tomography (OCT) B-scans. This method is time-consuming and laborious. We aimed to describe a novel and faster technique to obtain CT measurements.
In a prospective cohort study of 200 healthy eyes, Spectral-Domain OCT with enhanced depth imaging were performed with the Spectralis OCT using standardised imaging protocols. The OCT scans were independently graded by reading centre-certified graders. The standard method of manual adjustment of segmentation boundaries was performed. The new method consisted of adjusting only the lower segmentation line to the choroid-scleral boundary to generate the combined chorioretinal thickness, and subtracting the original retinal thickness (RT) from it to measure CT. Mean CT in the respective Early Treatment Diabetic Retinopathy Study (ETDRS) subfields were measured via the two methods, and were compared with intraclass correlation coefficients (ICC) and Bland-Altman plots.
The mean central subfield CT was 324.4 µm using the original method, compared with 328.8 µm using the new method, with a mean difference of 4.5 µm (range: -14.0 to +4.0 µm), and ICC for agreement of 0.9996 (p<0.001). Similar comparability was achieved for mean CT across all other ETDRS subfields, with mean differences ranging from 2.4 to 3.7 µm, and ICCs ranging from 0.99993 to 0.9996 (p<0.001).
Mean CT can be measured by subtracting the original RT from the combined chorioretinal thickness measurements. Only one segmentation line needs to be adjusted, instead of two, reducing time required for segmentation. This method is faster and reliable.
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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