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Shozo Sonoda, Taiji Sakamoto, Takehiro Yamashita, Hiroki Kawano, Naoya Yoshihara, Hiroto Terasaki, Makoto Shirasawa; Luminal and stromal areas of choroid determined by binarization method of optical coherence tomographic images. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2843.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the proportion of luminal and stromal areas of normal choroids in the optical coherence tomographic (OCT) images obtained by enhanced depth imaging (EDI)-OCT.
One hundred and eighty right eyes of 180 healthy volunteers without ocular pathology were studied. The choroidal images were recorded by EDI-OCT. The posterior choroid of the OCT images 7500 µm from the optic disc in the horizontal plane were converted to binary images by the Niblack method using ImageJ software. The total cross sectional choroidal area, lumina area, and stromal area of the choroid were individually measured. The correlations of each choroidal structure and the age, sex, axial length (AL), and refractive errors were calculated. The inter-rater agreement was also determined. The main measures were the correlations between clinical factors and each choroidal structure and ratio of luminal/stromal area.
The mean total cross sectional choroidal area was 1.84 mm2 (luminal area 1.21 mm2, and stromal area 0.63 mm2). The inter-rater agreement was significantly high for the cross sectional choroidal area with an intra-class correlation coefficient (ICC) of 0.990 [confidence interval (CI) 0.984-0.993] and a coefficient of variation (CV) of 0.37, the luminal area with ICC 0.990, (CI 0.986-0.993) and CV of 0.40, and the stromal area ICC of 0.970, (CI 0.957-0.978) and CV of 0.32. Multivariate analysis (standardized partial regression coefficient) showed that age (-0.723, P<0.001) was significantly correlated with the reduced area of the choroid and was greater than that for the AL (-0.408, P<0.001). The ratio of luminal/stromal area was significantly reduced by AL elongation (-0.531, P<0.001), and the strength of the correlation was greater than that induced by increasing age (-0.389, P<0.001).
The Niblack method with a publically-accessible software is helpful for analyzing the luminal and stromal areas of the choroid in the OCT images. Although both the luminal area and the stromal area decreased with increasing age and with elongation of the AL, the degree of decrease and areas affected were not the same.
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