Characteristics of Optic Disc Rotation in Myopic Eyes

To investigate the characteristics of optic disc rotation and ocular parameters affecting optic disc rotation in healthy myopic eyes.

Cross-sectional, comparative study.

A total of 220 participants with healthy myopic eyes.

Spherical equivalent (SE) refractive error, axial length, central corneal thickness, and intraocular pressure (IOP) were evaluated. Optic disc tilt ratio, degree of optic disc rotation, and area of β-zone parapapillary atrophy (PPA) were measured. Optic nerve head (ONH) parameters and thickness of the peripapillary retinal nerve fiber layer (pRNFL) and macular ganglion cell-inner plexiform layer (mGCIPL) were measured using Cirrus optical coherence tomography (Carl Zeiss Meditec Inc., Dublin, CA). Subjects were divided into 2 groups, group 1 with superior rotation and group 2 with inferior rotation of the optic disc, and various parameters were compared. Linear regression analysis was performed to evaluate the relationships between the degree of optic disc rotation and several parameters.

Degree of optic disc rotation.

Among 220 eyes, 147 showed superior rotation of the optic disc and 73 showed inferior rotation. The mean tilt ratio and rotation degree were 1.16 and -19.51°, respectively, in group 1 and 1.20 and 28.93°, respectively, in group 2, showing significant differences between the groups (P = 0.028 and P = 0.035, respectively). There were also significant between-group differences in IOP (15.59 vs. 16.34 mmHg), SE refractive error (-4.05 vs. -5.66 diopters [D]), axial length (25.51 vs. 26.26 mm), and area of β-zone PPA (0.32 vs. 0.70 mm(2)). Overall, a multivariate linear regression analysis showed that IOP, axial length, and area of β-zone PPA were significant parameters related to the degree of optic disc rotation (P = 0.011, P = 0.043, and P = 0.030, respectively). Group 2 showed thinner pRNFL and mGCIPL thickness in general compared with group 1.

In healthy myopic eyes, superior rotation of the optic disc was more prevalent than inferior rotation. As the optic disc rotates inferiorly, there was a significant positive correlation with IOP, axial length, and area of the β-zone PPA. Conversely, a significant negative correlation with pRNFL and mGCIPL thickness was observed.