Abstract
Purpose :
The foveal bulge is an arcuate structure located under the ellipsoid zone of cone photoreceptors and arises because the cone outer segments are longer and more concentrated. The presence or absence of a foveal bulge has been shown to be related to the visual acuity in various types of retinal diseases. However, it is difficult to examine the microstructure of the foveal bulge by conventional resolution SD-OCT. The purpose of this study was to determine the alignment of the vertex of the foveal bulge and the center of the foveal pit in normal eyes by ultrahigh resolution (UHR) SD-OCT.
Methods :
Fifteen eyes of 15 healthy volunteers (mean age 27.7 years, mean ocular axial length 23.8 mm; mean refractive error (spherical equivalent) -0.59 D) were studied. The horizontal and vertical B-scan images through the fovea were obtained by an UHR-SD-OCT instrument (β i-μ, KOWA, Japan). The vertex of the foveal bulge and the center of the foveal pit were manually identified with the imageJ software. The distance between the foveal bulge and foveal pit was measured in the horizontal and vertical images.
Results :
In the horizontal images, the vertex of foveal bulge existed on the nasal side of the center of the foveal pit in 13 eyes and on the temporal side in 2 eyes. In the vertical images, the vertex of foveal bulge existed superior to the center of foveal pit in 8 eyes, inferior to the center of foveal pit in 5 eyes, and same to the center of foveal pit in 2 eyes . The mean distance (± SD) between the vertex of foveal bulge and the center of foveal pit was 42.0 ± 28.7 μm in the horizontal images and 20.6 ± 16.4 μm in the vertical images.
Conclusions :
These results indicate that the vertex of the foveal bulge was not aligned with the center of the foveal peak in the emmetropic eyes of normal, young subjects with no PVD. This must be considered when interpreting the location of the vertex of the foveal bulge and the center of the fovea in eyes with retinal diseases.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.