A novel and faster method of manual grading to measure mean choroidal thickness using optical coherence tomography

Session Details

Session Title: Free Paper Session 21: Imaging III

Session Date/Time: Sunday 10/09/2017 | 08:00-09:30

Paper Time: 08:42

Venue: Room 113

First Author: : C.Tan SINGAPORE

Co Author(s): :    K. Cheong   L. Lim   K. Li                       

Abstract Details


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.


This was a prospective study conducted at Tan Tock Seng Hospital, National Healthcare Group Eye Institute, Singapore


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 measured 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 form the combined chorioretinal thickness, and subtracting the original retinal thickness (RT) from it. This would generate the new 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. The advantage of this method is that only one segmentation line needs to be adjusted, instead of two, hence reducing time required for segmentation. This method has been shown to be faster and reliable.

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