Focal lamina cribrosa defects are not associated with steep lamina cribrosa curvature but with choroidal microvascular dropout

Eun Ji Lee,Seung Hyen Lee,Jean Martial Mari,Michaël J A Girard,Tae-Woo Kim

doi:10.1038/s41598-020-63681-6

Abstract

Focal lamina cribrosa (LC) defects have been found to play an important role in the development and progression of glaucomatous optic neuropathy. However, the mechanism of generation of focal LC defects is largely unknown. This cross-sectional study was performed to investigate LC curvature and the frequency of parapapillary choroidal microvascular dropout (MvD) in glaucomatous eyes with focal LC defects. This study was conducted by a retrospective review of patients with primary open-angle glaucoma (POAG) included in an ongoing prospective study being performed at the Seoul National University Bundang Hospital (Investigating Glaucoma Progression Study). A total of 118 eyes of 118 patients with POAG, 59 with and 59 without focal LC defects, with eyes matched by age, axial length, and severity of visual field (VF) damage were included. Posterior LC bowing was assessed by calculating LC curvature index (LCCI), as the inflection of a curve representing a section of the LC, on the optic nerve head images obtained by enhanced-depth-imaging (EDI) spectral-domain optical coherence tomography (OCT). MvD was detected by OCT angiography. LCCI and MvD frequency were compared between eyes with and without focal LC defects. Mean LCCI was significantly smaller than in eyes with than without focal LC defects (9.75 ± 1.29 vs. 11.25 ± 1.39, P < 0.001). MvD was significantly more frequent in eyes with than without focal LC defects (84.7% vs. 49.2%, P < 0.001). MvD in eyes with focal LC defects showed a strong topographic correlation with the focal LC defects. These findings suggest that focal LC defects may primarily result from vascular factors rather than from mechanical strain.

Highlights

Focal lamina cribrosa (LC) defects have been found to play an important role in the development and progression of glaucomatous optic neuropathy
After matching for age, axial length, and mean deviation of visual field test between patients with and without focal LC defects, 59 eyes of 59 patients with primary open-angle glaucoma (POAG) were included in each group
This study demonstrated that the average LC curvature index (LCCI) and LCCIs measured in the seven horizontal B-scans were significantly smaller in glaucomatous eyes with than without focal LC defects when eyes were matched for age, axial length and glaucoma severity

Summary

Introduction

Focal lamina cribrosa (LC) defects have been found to play an important role in the development and progression of glaucomatous optic neuropathy. The mechanism of generation of focal LC defects is largely unknown This cross-sectional study was performed to investigate LC curvature and the frequency of parapapillary choroidal microvascular dropout (MvD) in glaucomatous eyes with focal LC defects. LC compression may induce collapse of capillaries inside the laminar beams leading to optic nerve ischemia The rate of visual field worsening was faster in eyes with than without focal LC defects[9] These findings suggested that focal LC defect is likely have important pathogenic relevance to glaucomatous optic neuropathy. MvD is regarded as a true impairment of perfusion, based on its correspondence to the perfusion defect identified by indocyanine green angiography[11] These observations suggested that the development of focal LC defect is associated with vascular compromise. It is unclear whether stress induced by intraocular pressure (IOP) plays a significant or more important role than vascular factors in the development of focal LC defects

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