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It is estimated that by the year 2050, approximately 50.0 % of the world’s population will be myopic. It has been suggested that the thickening sub-foveal choroidal thickness (SFChT) is a precursor for reduced eye growth and slowed myopia progression. Hence, it is highly important to identify structural changes, during myopia management. Literature suggests that the SFChT show short-term changes and has been proposed as an ocular marker for many ocular conditions including pathological myopia. A major limitation to its use is that none of the commercially available instruments give a direct measure of SFChT. This paper describes a new semi-automated method for quantification of the SFChT using ocular biometry. This image processing method is used on healthy pediatric myopes to quantify the SFChT. Both axial length (AXL) and SFChT were quantified from a 2-D A-scan graph generated from an ocular biometer (ARGOS, Aichi, Japan). An experienced clinician manually selected three peak points corresponding to anterior corneal, retinal, and choroidal peaks which were used as the input to the algorithm. Using the pixel properties, the overall AXL was calculated by subtracting the distance between the anterior corneal and retinal peak. Similarly, the SFChT was calculated as the distance difference between retinal and choroidal peaks. These calculated values were compared with a standard clinical method. The intraclass correlation coefficient ICC showed a good (κ=0.79, CI: 0.63 – 0.87) agreement between the methods. Similarly, the Bland-Altman plot showed a good agreement (The mean difference between the two methods was -21.28 μm) with a wide limit of agreement (LOA: 79.08 & -121.64 μm). Compared to SS-OCT method and new-semi automated method, there is significant overestimation of SFChT (p<0.001). However, there is moderate agreement between these two methods.
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