Abstract
The center of the fovea, termed the foveola, is the area of highest visual acuity, has the highest density of cone photoreceptors. We investigated the distance between the automatically-determined center of the foveal avascular zone (FAZ) and the manually-determined highest foveal bulge (FB) point using single swept-source optical coherence tomography angiography (OCTA) instrument. This cross-sectional study included 49 eyes of 49 individuals (34 women and 15 men; median age: 68 years) with no history of ocular disorders. The FAZ in the superficial capillary plexus was automatically determined using the Kanno–Saitama macro method, and the center of the FAZ was automatically determined using ellipse approximation. Another candidate foveal center, the highest FB point, was determined manually on the serial cross-sectional B-scan images. As a result, the foveal center was manually identified as the highest FB point on B-scan OCTA images. The center of the FAZ was more likely to be located inferior to the highest FB point (p = 0.031). In participants with a total (linear) distance of more than 50 μm between the center of the FAZ and the highest FB point, the displacement was significantly more in the horizontal direction than in the vertical direction (p = 0.017). These results can be applicable to further studies regarding the spatial relationships between the center of the FAZ and the highest FB point in various macular diseases or previously-treated eyes.
Highlights
The center of the fovea, termed the foveola, is the area of highest visual acuity, has the highest density of cone photoreceptors and the smallest thickness of the fovea, and is the center of the foveal avascular zone (FAZ)[1,2]
This study investigated the positional relationship between en face OCTA-derived center of FAZ using an automated FAZ extraction program, and the manually-determined highest foveal bulge (FB) point, which is determined as in the previously reported method, using cross-sectional B scan images obtained from the single OCTA system in elderly healthy eyes
The decimal best-corrected visual acuity (BCVA) values were converted to logarithm of the minimum angle of resolution values
Summary
The center of the fovea, termed the foveola, is the area of highest visual acuity, has the highest density of cone photoreceptors and the smallest thickness of the fovea, and is the center of the foveal avascular zone (FAZ)[1,2]. Optical coherence tomography (OCT) is a non-invasive imaging technology used to acquire high-resolution, 3D, cross-sectional images of the retina, and is one of the most important ancillary tools for the diagnosis and management of macular diseases[3,4] Both spectral-domain OCT (SD-OCT) and swept-source OCT (SS-OCT) provide detailed and in vivo analyses of the interior of the retina, especially the fovea, which is the area with the highest visual acuity. Previous studies of B scan images of healthy eyes have reported that the ellipsoid zone (EZ) has a bulge at the central fovea[5,6] This point is defined as the foveal bulge (FB) and is regarded as the center of the fovea[5,6,7]. This study investigated the positional relationship between en face OCTA-derived center of FAZ using an automated FAZ extraction program, and the manually-determined highest FB point, which is determined as in the previously reported method, using cross-sectional B scan images obtained from the single OCTA system in elderly healthy eyes
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