Association between optic disc deformation and lamina cribrosa defects detected on swept-source optical coherence tomography in highly myopic eyes with glaucoma

Abstract

Purpose: Focal lamina cribrosa (LC) defects are reportedly associated with local glaucomatous optic disc changes such as neuroretinal rim thinning/notching and acquired pit of the optic nerve. In this study, we investigated LC defects in highly myopic glaucomatous eyes using 3-dimensional swept-source optical coherence tomography (SS-OCT) and evaluated the association between LC defect location and optic disc parameters indicative of its deformation.

Methods: The eyes (n = 111) of 65 primary open angle glaucoma patients with a spherical equivalent (SE) <-6 diopters were examined with SS-OCT. Mean age of the patients was 51.4 years, mean SE was -9.5 diopters, and mean MD value of the Humphrey visual field analyzer 24-2 program was -11.3 dB. A reference line between the center of the disc and the foveal pit was determined in each eye using SS-OCT fundus photography. The number of LC defects was counted in each eye, and the location was determined by the reference line. The area of peripapillary atrophy (PPA) was measured with a color fundus photograph using image J software, and the PPA area was divided into superior and inferior areas by the reference line. Ovality index and torsion angle of the optic disc (angle of cyclotorsion) were also measured with originally developed software.

Results: LC defects were detected in 46 of 111 eyes (41.4%). Sixteen eyes had a larger number of LC defects in the superior hemisphere (SH group), and 30 eyes had a larger number of defects in the inferior hemisphere (IH group). The area of PPA was larger in the superior hemisphere in 7 eyes of the SH group and 3 eyes of the IH group, whereas it was larger in the inferior hemisphere in 9 eyes of the SH group and 27 eyes of the IH group; this difference was statistically significant (P = 0.02, Fisher exact probability test). The mean cyclotorsion angle was 1.6° in the SH group and 10.3° in the IH group. Mean ovality index was 0.69 in the SH group and 0.72 in the IH group. The optic disc in the IH group was significantly more inferotemporally distorted than in the SH group, whereas no significant differences were found for tilt (cyclotorsion, P = 0.02; ovality index, P = 0.46; unpaired t test).

Conclusions: LC defects were frequently detected in highly myopic eyes with glaucoma. LC defects may be associated with deformation of the optic disc.

Keywords: 627 optic disc • 550 imaging/image analysis: clinical • 605 myopia