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Pukhraj Rishi, Zeeshan Akhtar, Rupesh Agrawal, Ekta Rishi, Ashutosh Agarwal; Choroidal structural analysis and choroidal vascularity index in normal Indian subjects – A study of 460 eyes. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1509.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate Choroidal Vascularity Index (CVI) amongst normal healthy subjects from India.
This was a prospective, observational, cross-sectional study with 460 eyes of 230 normal healthy subjects. Choroidal measurements including total circumscribed choroidal area (TCA), luminal area (LA), stromal area (SA) and subfoveal choroidal thickness (SFCT) were taken using Swept Source OCT. CVI was obtained using an open source software (ImageJ) with Modified Niblack method to delineate stromal and luminal areas of the choroid. Ratio of LA to TCA gives CVI. Ratio of LA to SA was also calculated as a measure of choroidal vascularity.
The mean age of the patients was 42.1(±17.6) years. The mean TCA in the right and left eye was 0.91(±0.18) and 0.91(±0.17) mm2 respectively. The mean LA in right and left eye were 0.61(±0.14) and 0.61(±0.13) mm2 respectively. Similarly, the mean stromal area (SA) measured 0.3(±0.06) mm2 in the right eye while that in the left eye was 0.3(±0.06) mm2. The mean ratio of LA to SA was 2.04(±0.36) and 2.03(±0.37) in the right and the left eye respectively. The mean CVI in the right eye was 66.66 (±3.83) % while in left eye was 66.59 (±3.78) %.The highest CVI in right eye (67.81%) is in the 50 to 60 years age group, while that for left eye is in the 70 to 80 years age group. The highest TCA and LA in both eyes are in the 20 to 30 years age group. All choroidal parameters are significantly different between age groups(p<0.05)In the right eye, mean CVI had a significant and high positive correlation with the ratio of LA to SA (r=0.986, p<0.01). Similarly, in the left eye, mean CVI had a significant and high positive correlation with the ratio of LA to SA (r=0.98, p<0.01). Linear regression analysis was done to determine the factors affecting CVI for both eyes. For the right eye, TCA and LA were found to affect CVI significantly. TCA was found to inversely affect CVI (p<0.01) whereas LA was found to directly affect CVI (p<0.01). For the left eye, TCA (p<0.01) were found to be linearly related to CVI, while SA was inversely related (p<0.01).
CVI of normal healthy Indian subjects seemed comparable to that of other studies. Our study further validates the method of image binarisation and segmentation to quantitatively measure choroidal parameters.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Composite image shows orientation of line scans on swept source OCT
Binarised image of Figure 1
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