Deviation in the Position of Foveal Bulge from Foveal Center in Normal Subjects Measured Using Spectral-Domain OCT

Abstract

To report a deviation in the position of the foveal bulge (FB) from the foveal center and to analyze its relationship with the foveal shape in normal subjects using spectral-domain (SD) OCT. Cross-sectional study. A total of 146 clinically normal subjects. Macular Cube 512× 128 was used to obtain the cross-sectional images of the macula in Cirrus HD-OCT (Carl Zeiss Meditec, Inc, Dublin, CA). The foveal center was identified manually as the deepest point within the foveal dip, which was termed the "manually identified foveal center" (MFC). The position of the FB with respect to the MFC was noted, and the radial distance between them was measured. The foveal center detected by the inbuilt auto-fovea finder algorithm was considered as the automatically detected foveal center (AFC), and the distance between the AFC and the FB was measured. The radial distances of the FB from the MFC and the AFC were compared, and its direction of deviation from the foveal center was noted. All OCT measurements were adjusted for the ocular magnification factor. The amount of deviation was correlated with the foveal shape parameters, such as foveal radius. Radial distance between FB and foveal center and its direction of deviation. Mean age of the subjects was 43.9±14.4 years. The position of the FB was deviated from the foveal center in 125 subjects (85.6%). Median radial distance between the FB and the MFC was 58.6 μm (35.16-75.04 μm) with the maximum separation of 222.68 μm. From the AFC, the FB was separated by a median of 58.6 μm (46.88-84.51 μm), maximum separation being 181.94 μm. The direction of deviation of the FB from foveal center was nasal in a majority of subjects (n= 75, 51% in MFC). The separation between the FB and the foveal center was not associated with age (P=0.149), gender (P= 0.762), or axial length (P= 0.25). The position of the FB did not coincide with the foveal center and was deviated in the direction of the optic disc in a majority of normal subjects. Further studies are required to correlate this anatomic deviation with the fixation locus of the individuals.