Fig 1.
Determination of the position of central retinal vessel trunk (CRVT) within the lamina cribrosa (LC) using swept-source optical coherence tomography (SS-OCT) radial-scan images.
A, B SS-OCT infrared images of eyes with a central CRVT (A) and a peripheral CRVT (B). The green markings with numbers indicate the location at which the radial images were obtained. Images obtained at locations 11 (A) and 12 (B) were used to determine the CRVT position for each eye. C, D B-scan images containing the CRVT. The CRVT is shown as a hyporeflective shadow penetrating the LC (yellow arrows). E, F These images are the same as the above B-scan images after adaptive compensation. Red glyphs indicate the point of anterior LC insertion and vertical dashed lines indicate the locations dividing the anterior LC surface diameter (white solid lines) into five equal parts. Determination of the CRVT position was based on the location of the CRVT exit at the level of the anterior LC surface. (E) The CRVT exit in this eye is located within the central one-fifth of the anterior LC surface diameter (yellow arrow), and thus this eye was categorized into the central group. (F) The CRVT of this eye is outside the central one-fifth of the anterior LC surface diameter (yellow arrow), and thus this eye was assigned to the peripheral group. Note that the anterior LC surface depth is smaller in the eye with a central CRVT (E) than in that with a peripheral CRVT (F).
Fig 2.
Measurement of the anterior lamina cribrosa (LC) surface depth (LCD).
A. Infrared image indicating the locations where the 11 B-scan images were selected for the LCD measurements (horizontal lines). B. B-scan image at the location corresponding to the green horizontal line in panel A. The LCD was determined by measuring the distance from Bruch’s membrane opening plane to the level of the anterior LC surface. A reference line connecting the two termination points of Bruch’s membrane (red glyphs) was drawn in each B-scan, and the distance from that reference line to the level of the anterior border of the LC was measured at three points (green glyphs). The average of the three values was defined as the LCD in the selected B-scan.
Table 1.
Demographics and baseline characteristics.
Table 2.
Factors influencing the mean LC depth.
Fig 3.
Anterior lamina cribrosa surface depth (LCD) profiles in the 11 horizontal equidistant B-scan images (scans 1–11 are from superior to inferior) according to central retinal vessel trunk (CRVT) location (A), age (B), untreated intraocular pressure (IOP; C), and global retinal nerve fiber layer (RNFL) thickness (D).
The cutoff values for continuous variables (age, untreated IOP, and RNFL thickness) for dividing the eyes into two subgroups were obtained by the regression-tree method using GUIDE Classification and Regression Trees and Forests software. Note that overall the anterior lamina cribrosa surface is W-shaped with a central elevation, or has a sloped or focally concave configuration without a central elevation. Error bars represent the 95% confidence interval. *Significantly different at P≤0.01; **significantly different at P≤0.001.
Fig 4.
Correlation between the mean anterior lamina cribrosa surface depth (LCD) and age (A), untreated intraocular pressure (IOP; B), and retinal nerve fiber layer (RNFL) thickness (C), according to the location of the central retinal vessel trunk (CRVT).
Note that the correlations between age and mean LCD (A), and between untreated IOP and mean LCD (B) were more prominent in the peripheral CRVT group than in the central CRVT group.