Abstract
Purpose :
Vessel density (VD) measurements using OCT angiography (OCTA) have become a widely used technique to assess the circulation status of various ocular tissues. Conventionally, VD is computed on a two-dimensional (2D) projection image that may underestimate the actual VD, especially on a thick tissue segment due to masking of underlying vessel structures. The purpose of this study was to assess the relationship of a newly developed three-dimensional (3D) VD measurement to structural measurements, such as retinal nerve fiber layer (RNFL) and ganglion cell inner plexiform layer (GCIPL) thickness, in comparison to conventional 2D VD measurements.
Methods :
One eye each from 17 healthy and 10 glaucoma subjects were scanned with a commercial OCTA device (Angioplex; Zeiss; Dublin, CA). After manually marking the anterior surface of the lamina cribrosa, both 2D and 3D VD of the pre-laminar tissue were measured using software of our own design. 3D VD was measured by counting the number of voxels categorized as vasculature divided by the total number of voxels within a given volume. Both a manually delineated optic disc margin (whole disc) and temporal section of the optic disc inside the major vessel arcade (temporal) were used for analysis. Multivariable regression analyses determined the association of 2D and 3D VD with mean circumpapillary RNFL and GCIPL thicknesses.
Results :
Subjects demographics are summarized in Table 1. In whole disc analysis, no significant associations were detected between 2D or 3D VD and RNFL and GCIPL thickness. Measured pre-laminar thickness was 518 ± 95 (healthy) and 496 ± 104 m (glaucoma) for the whole disc section, and 416 ± 109 (healthy) and 417 ± 108 μm (glaucoma) for the temporal section, which were equivalent to or thicker than the total retinal thickness. However, in temporal analysis, there was no association with RNFL but a one unit increase in VD density was significantly associated with an increase of 0.30 µm in GCIPL thickness (p = 0.017). No association was detected with 2D VD.
Conclusions :
Pre-laminar microvasculature VD is significantly associated with GCIPL thickness only with 3D measurements. Because the temporal aspect of the optic nerve is most related to the macular region, our findings suggest that 3D VD measurements may be a more suitable biomarker than 2D VD measurements.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.