Abstract
Purpose :
To compare the fractal dimensions of the peripapillary intervascular spaces as obtained by optical coherence tomography angiography (OCT-A) between primary open-angle glaucoma (POAG) and controls.
Methods :
Seventy (70) POAG patients and 50 control subjects underwent 20°X20° scan of Spectralis OCT-A to evaluate peripapillary microvasculature using pre-defined slabs: 1) the superficial vascular complex (SVC) and 2) the avascular complex (AVC). The en-face image of each slab was processed by ImageJ software in order to calculate the vessel density and the fractal dimension of intervascular space using the box-counting method. The utilities of the parameters for discriminating between the POAG and control groups were assessed using areas under the receiver operating characteristic (ROC) curves (AUCs).
Results :
POAG group had the lower fractal dimensions of intervascular spaces in both SVC (P<0.001) and AVC (P=0.010) slabs. The fractal dimension of intervascular space correlated with vessel density in both SVC (r=0.884, P<0.001)) and AVC (r=0.643, P<0.001) slabs. In a multivariable regression analysis, the SVC fractal dimension showed negative correlations with age (P<0.001) and axial length (P<0.001) and a positive correlation with average retinal nerve fiber layer (RNFL) thickness (P<0.001). The AVC fractal dimension showed a negative correlation with glaucoma diagnosis (P=0.026) and a positive correlation with the Bruch’s membrane opening (BMO) size (P=0.004). In terms of diagnostic utility, the AUC of the SVC fractal dimension (AUC=0.767) was significantly larger than that of the SVC vessel density (AUC=0.709, P=0.032), while it was smaller than that of the average RNFL thickness (AUC=0.867, P=0.016).
Conclusions :
The fractal dimension of intervascular space represented the complexity of vascular network and was different from the conventional vessel density. Therefore, it could be another marker of assessing peripapillary microvasculature using OCT-A.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.