What is the role of magnification correction in the measurement of macular microvascular dimensions in emmetropic eyes?

V. K. Viekash; Janarthanam Jothi Balaji; Vasudevan Lakshminarayanan

doi:10.1117/12.2610713

4 March 2022 What is the role of magnification correction in the measurement of macular microvascular dimensions in emmetropic eyes?

V. K. Viekash, Janarthanam Jothi Balaji, Vasudevan Lakshminarayanan

Author Affiliations +

Proceedings Volume 11941, Ophthalmic Technologies XXXII; 119410L (2022) https://doi.org/10.1117/12.2610713
Event: SPIE BiOS, 2022, San Francisco, California, United States

Conference Poster

Abstract

The foveal avascular zone (FAZ), as visualized by optical coherence tomography angiography (OCTA), has distinct parametric characteristics. These metrics can help us understand FAZ variations in various ophthalmic conditions such as diabetic retina, retinopathy of prematurity, glaucoma, and pathological myopia. One of the several factors that influence the accuracy of these measures is the eye's axial length (AXL). Even though the OCTA is designed to image the retina with a standard AXL of 23.95 mm, there is considerable variation even in normal healthy eyes; for example, the average Indian's AXL is 23.34 ± 1.12 mm, which would result in retinal image magnification changes It has been reported that, if the FAZ area is not corrected for AXL, there can be up to a 51.0 % deviation in the measured parameters. Bennett's correction (and variations) are commonly employed to determine axial magnification. This study compares the effects of magnification in emmetropic Indian eyes with and without Bennett's correction. The FAZ dimensions were measured in healthy normal Indian subjects with a mean ± SD of 27.38 ± 11.62 years, AXL 23.40 ± 0.88 mm, and mean spherical equivalent of 0.08 ± 0.24 D using a newly designed automated image processing approach. Our results indicate no need to correct axial length variations over a 23.18 to 24.01 mm range in emmetropic eyes. This implies that any AXL longer than 24.01 mm and smaller than 23.18 mm may require axial magnification correction to precisely measure FAZ parameters.

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V. K. Viekash, Janarthanam Jothi Balaji, and Vasudevan Lakshminarayanan "What is the role of magnification correction in the measurement of macular microvascular dimensions in emmetropic eyes?", Proc. SPIE 11941, Ophthalmic Technologies XXXII, 119410L (4 March 2022); https://doi.org/10.1117/12.2610713

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