In-vivo, 3-Dimensional Imaging of the Lamina Cribrosa Horizontal Central Ridge in Normals and Lamina Cribrosa Deformation in Glaucoma

Abstract

 

Purpose:

 

To compare the morphology and position of the lamina cribrosa (LC) between high-tension glaucoma (HTG) and normal subjects using enhanced depth imaging spectral-domain optical coherence tomography (EDI SD-OCT).

 

Methods:

 

Serial horizontal and vertical B-scans of the optic nerve head were obtained using EDI SD-OCT and a 3D image of LC was reconstructed for one eye of each HTG and normal subject. Mean and maximum LC depths were measured in 11 equally spaced horizontal B-scans, and the depth of LC insertion was measured at 32 points along its circumference (reference plane: Bruch’s membrane edges) (Fig A,B). Depth profiles were compared between the two groups.

 

Results:

 

A total of 56 HTG (visual field [VF] mean deviation, -16.2±3.1 dB) and 31 normal subjects were included. In normals, 3D imaging (Fig C) and W-shaped depth profiles of LC and LC insertion (Fig D,E) revealed a fusiform horizontal central ridge of LC. The vertical diameter of LC and the angle of optic nerve tilting had a significant negative correlation with LC depth (P<0.03). Mean and maximum LC depths were significantly greater in the HTG group before and after controlling for those factors (posterior bowing, Fig D). The LC insertion depth was significantly greater in the HTG group in the superior and inferior regions (posterior sliding of LC insertion, Fig E). The depths of LC and LC insertion in the eyes with a VF defect limited to the superior hemifield were significantly greater than those in normals in the inferior region (Fig F,G), where the retinal nerve fiber layer (RNFL) was significantly thinner than normals (P<0.01).

 

Conclusions:

 

Mechanisms of LC deformation in HTG include posterior bowing of the LC and posterior sliding of the LC insertion, and localized LC deformation corresponds to regions of RNFL and VF defects. The horizontal central ridge, which acts as a LC structural support, appears to be unaffected by elevated IOP.  

 

Keywords: lamina cribrosa • imaging/image analysis: clinical • anatomy