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Kyoung Min Lee, Martha Kim, Sohee Oh, SeokHwan Kim; Shape of globe expansion determines the optic nerve head configuration. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6193. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the association between the morphology of optic nerve head (ONH) and the spherical shape of eyeball.
Among the subjects who had been enrolled in the Boramae Glaucoma Imaging study with a diagnosis of glaucoma or glaucoma suspect, 108 eyes from 108 subjects who had Magnetic Resonance Imaging (MRI) scans of eyeball were included retrospectively. Spherical shape of eyeballs was classified according to the dimension of the longest diameter in the MRI scans: group 1 with axial dimension (prolate sphere), group 2 with horizontal dimension (horizontally oblate sphere), and group 3 with vertical dimension (vertically oblate sphere). The ONH morphology was evaluated in the aspect of the angular deviation of vascular trunk and the angular location of the longest externally oblique border from the center of Bruch’s membrane opening (BMO). For this purpose, the BMO was delineated by OCT imaging, and the angular deviation of vascular trunk was measured with the horizontal nasal midline as 0° and the superior location as a positive value, while the angular location of the longest externally oblique border was measured with the horizontal temporal midline as 0° and the superior location as a positive value.
Fifty-four eyes (50%) had a prolate shape (group 1), 34 eyes (31%) with a horizontally oblate shape (group 2), and 20 eyes (19%) with a vertically oblate shape (group 3). Prolate shape was associated with longer axial length and lesser angular deviation of vascular trunk from the horizontal midline. The position of vascular trunk was in the nasal side in group 1, in the temporal side in group 2, and along the vertical meridian in group 3. The externally oblique border was observed in 56 (52%) of subjects, and the angular location of the longest part was in the direction opposite to the vascular trunk position. A logistic regression analysis revealed that the angular deviation of the vascular trunk was the only associated factor of oblateness (OR = 1.035, P = 0.004).
The vascular trunk position within the BMO was determined by the spherical shape of eyeballs. It represented the different lengthening of the layers above and below the BMO during eyeball expansion thereby inducing the lamina cribrosa shift.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Measurement of eyeball shape and the optic nerve head morphology
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