Purpose:
To assess size, position and depth of the lamina cribrosa (LC) in normal subjects and their relationships with each other and with axial length, age and intraocular pressure (IOP).
Methods:
The mean and maximum LC depths in normal eyes were measured in 3 horizontal enhanced depth imaging optical coherence tomography (EDI OCT) B-scans (midline, mid-superior and mid-inferior; Fig. A-D). The sizes of the optic disc, Bruch’s membrane opening (BMO) and LC, defined as the average of their maximum horizontal and vertical diameters, were measured from serial horizontal and vertical EDI OCT B-scans of the optic nerve head (interval between scans: approximately 30 µm). Using the horizontal midline EDI OCT B-scan, the LC displacement from the BMO was measured as an angle (θ) (Fig. E). Univariate and multivariate correlation analyses were performed between these measured variables (the sizes of the optic disc, BMO and LC, the mean and maximum LC depths, and |θ|), axial length, age and IOP.
Results:
45 eyes (45 subjects) were included (mean age and axial length: 41±17 yr and 24.4±1.4 mm [range: 21.9 to 27.8], respectively). The LC size (1893±205 μm [range: 1437 to 2397), the LC displacement (θ) (29±29 degrees [range: -45 to 78]) and the mean (348±76 µm [range: 240 to 499]) and maximum (399±81 µm [range: 276 to 561]) LC depths varied considerably among eyes. The LC size significantly correlated with the optic disc size (P=0.002, R=0.587) and the BMO size (P=0.001, R=0.603), but not with axial length, age or IOP (all P>0.3). The absolute LC displacement (|θ|) significantly correlated with axial length (P0.1). Both mean and maximum LC depths significantly correlated with the LC size (P=0.006, R=-0.533 for mean LC depth; P=0.007, R=-0.526 for maximum LC depth) and the absolute LC displacement (|θ|) (P=0.018, R=-0.471 for mean LC depth; P=0.029, R=-0.439 for maximum LC depth), but not with axial length, age or IOP (all P>0.2). In the multivariate analysis, the correlation of LC depth with the LC size and the absolute LC displacement (|θ|) remained significant (P≤0.036).
Conclusions:
The LC size, position and depth vary considerably among eyes. The LC depth has a moderate correlation with the LC size and displacement.
Keywords: optic nerve • lamina cribrosa • anatomy