Positional Change of Optic Nerve Head Vasculature during Axial Elongation as Evidence of Lamina Cribrosa Shifting: Boramae Myopia Cohort Study Report 2

Abstract

Purpose: To investigate the positional change of central retinal vasculature and vascular trunk to deduce the change in the lamina cribrosa (LC) during axial elongation.

Design: Prospective cohort study.

Participants: Twenty-three healthy myopic children (46 eyes).

Methods: Participants had undergone a full ophthalmologic examination and axial length measurement every 6 months for 2 years. Using spectral-domain OCT, circle scans centered around the optic disc in the glaucoma progression analysis mode, which enabled capturing of the same positions throughout the entire study period, and enhanced depth imaging of the deep optic nerve head complex were performed. Infrared imaging of the circle scans was used to measure the changes in the angles between the first and final visits. The angle between the major superior and inferior retinal arteries was measured along the circle scan twice: from the center of the circle scan and from the central retinal vascular trunk, respectively. The positional change of the retinal vascular trunk also was measured.

Main outcome measures: Change in vascular angle and position of vascular trunk with axial elongation and associated factors.

Results: The vascular angle measured from the center of the circle scan did not change (P = 0.247), whereas the angle measured from the central retinal arterial trunk decreased with axial elongation (P < 0.001). A generalized estimating equation analysis revealed that the factors associated with angle decrease were axial elongation (P = 0.004) and vascular trunk dragging (P < 0.001). The extent of vascular trunk dragging was associated with axial elongation (P < 0.001) and increased border length with marginal significance (P = 0.053), but the extent of dragging could not be explained fully by their combination. The major directionality of dragging was mostly to the nasal side of the optic disc, with large variations among participants.

Conclusions: During axial elongation, the retinal vasculature at the posterior pole was unchanged, whereas the position of the central vascular trunk was dragged nasally. Because the central retinal vascular trunk is embedded in the LC, its dragging indicates nasal shifting of the LC, which could explain the vulnerability of myopic eyes to glaucomatous optic neuropathy.