Abstract
PurposeThe lamina cribrosa (LC) is known to play a critical role in the pathogenesis of glaucoma. Although it has been reported that striae-shaped or slit-shaped lamina pores are more frequent in eyes with primary open angle glaucoma (POAG), this observation is based only on fundus photography. The primary object of this study is to perform layer-by-layer comparisons of the shape of lamina pores within the LC in vivo.DesignCross-sectional study.MethodsOptic nerve head B-scans were obtained using custom-made broad-wavelength optical coherence tomography with a mode-locked laser. A total of 300 single B-scans per eye were obtained and three-dimensional images were rendered from these image sequences to obtain 2-μm thin-slice en face images of the LC. Elongation indices (EIs) of the lamina pores were measured from the anterior surface (AS) of the LC to the deeper layers in 40-μm increments.ResultsThirteen eyes from 10 primary open angle glaucoma (POAG) patients of mean deviation -15.2 (-16.5, -12.9) (median [25,75 percentile]) dB and 10 eyes from 7 normal controls were studied. Although the EI value was not significantly different between the superior, temporal and inferior regions of the LC at any depth level in either group, it was greater at the AS than at the 40 μm and 80 μm depth levels (P < .001) in both groups, and was greater in the POAG group only at the AS and 40 μm depth level (P ≤ .05). After adjustment for age and refraction, the effects of depth and presence of POAG on the EI value remained significant. Also, the severity of glaucoma and depth were significant factors associated with EI in multivariate analysis.ConclusionsElongation of lamina pores was significantly more evident at the anterior surface and the 40-μm depth level of the LC in POAG eyes than in normal eyes, suggesting that nerve fiber bundles passing through the LC were under greater stress in the anterior layers of the LC.
Highlights
The lamina cribrosa (LC) is a porous connective tissue, through which the axon bundles of retinal ganglion cells travel in transit to the orbital portion of the optic nerve
Elongation indices (EIs) of the lamina pores were measured from the anterior surface (AS) of the LC to the deeper layers in 40-μm increments
Elongation of lamina pores was significantly more evident at the anterior surface and the 40μm depth level of the LC in primary open angle glaucoma (POAG) eyes than in normal eyes, suggesting that nerve fiber bundles passing through the LC were under greater stress in the anterior layers of the LC
Summary
The lamina cribrosa (LC) is a porous connective tissue, through which the axon bundles of retinal ganglion cells travel in transit to the orbital portion of the optic nerve. The LC is known to play a critical role in the pathogenesis of glaucoma.[1,2,3] Histopathological studies have reported various changes in the structure of the LC, such as thinning, posterior displacement, and decreased density of connective tissue, which are believed to be associated with key mechanisms underlying the retinal nerve fiber damage observed in glaucoma.[3,4,5,6,7] Miller et al reported that striae-shaped or slit-shaped lamina pores were more frequent in eyes with advanced field loss.[8] this observation was mainly based on ophthalmoscopic observations or fundus photography, and the precise shape of the lamina pores within and on the surface of the LC was not determined. The LC is partially hidden behind the converging retinal nerve fibers, and only a small portion is generally visible at the base of the optic cup in fundus photographs of normal eyes. Nerve fiber bundles passes through the lamina pores, the shape of laminar pores within LC may play an important role in the pathogenesis of glaucoma
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