Lamina cribrosa configuration in tilted optic discs with different tilt axes: a new hypothesis regarding optic disc tilt and torsion.

PURPOSE To determine the configuration of the anterior lamina cribrosa (LC) surface in eyes with different tilt axes. METHODS A total of 114 eyes (66 glaucomatous eyes and 48 healthy eyes) with tilted optic discs (ovality index > 1.3) were divided into vertical- and horizontal-tilt groups according to their optic disc tilt axis. Serial horizontal B-scan images of the ONH were obtained from each eye using enhanced-depth imaging spectral-domain optical coherence tomography. After three-dimensional reconstruction of the images, the anterior LC surface depth (LCD) was measured in each of the oblique scans containing the long disc axis and in the seven horizontal B-scans that divided the anterior LC surface vertically into eight parts. RESULTS The configuration of the anterior LC surface along the long disc axis differed markedly between groups. The vertical-tilt group had a larger LCD at superior locations than at inferior locations, while the pattern was the opposite in the horizontal-tilt group. The RNFL thinning in glaucomatous eyes was most prominent at both the superotemporal and inferotemporal sectors in the vertical-tilt group, while it was predominated at the inferotemporal sector in the horizontal-tilt group. CONCLUSIONS The configuration of the anterior LC surface in eyes with differed optic disc tilt axis suggested that the horizontally-tilted optic discs may not be resulted from the optic disc rotation, but from the optic disc tilt centered on the oblique axis. The preferential location of RNFL thinning could be explained by the LCD profile differing according to the tilt axis.