Comparison of Diagnostic Accuracy of Peripapillary Vessel Parameters from 4.5x4.5mm and 6x6mm SD-OCTA Scans for Glaucoma

Abstract

Purpose : OCT Angiography (OCTA) is a non-invasive imaging technique that has potential to serve as a diagnostic tool for glaucoma by detecting microvascular changes in the superficial retina at an early stage. We compared diagnostic ability of peripapillary vessel parameters from 4.5x4.5mm ("4.5") and 6x6mm ("6.0") OCTA scans. We hypothesized that 4.5 scans result in higher diagnostic accuracy due to improved resolution and that no additional diagnostic information is gathered from more peripheral areas in 6.0 scans.

Methods : 4.5 and 6.0 scans were exported from prototype and commercial spectral domain OCTA, respectively, and processed using custom quantification software to create en face images of the superficial retinal layers on normal (30 eyes, 19 patients) and primary open angle glaucoma (53 eyes, 39 patients; pre-perimetric to severe) eyes. Perfusion was quantified using four parameters: vessel area density (VAD), vessel skeleton density (VSD), vessel complexity index (VCI), and flux for the entire scan area and the same 1mm annulus scan area around the optic nerve head in 4.5 and 6.0 scans. Area-under-curve (AUC) statistics controlled for age and inter-eye correlation.

Results : For quantification of the global scan area, the AUCs for 4.5 versus 6.0 scans, respectively, were 0.82 (p<.0001) and 0.87 (p<.0001) (AUC difference [Δ]: p=.20) for VAD, 0.77 (p<.0001) and 0.88 (p<.0001) (Δp=.02) for VSD, 0.57 (p=.29) and 0.78 (p<.0001) (Δp= .0002) for VCI, and 0.90 (p<.0001) and 0.89 (p<.0001) (Δp=.64) for flux.
For quantification of the annulus scan area, the AUCs for 4.5 versus 6.0 scans, respectively, were 0.77 (p<.0001) and 0.86 (p<.0001) (Δp=.07) for VAD, 0.70 (p=.0006) and 0.81 (p<.0001) (Δp=.03) for VSD, 0.59 (p=.18) and 0.62 (p=.06) (Δp= .42) for VSD, and 0.89 (p<.0001) and 0.91 (p<.0001) (Δp=.55) for flux.

Conclusions : The vessel parameters for 6.0 scans outperformed those for 4.5 scans, suggesting more peripheral areas may have diagnostically relevant information. While the 4.5 scans used slightly different prototype image processing methods, it is possible that improved resolution does not provide increased diagnostic accuracy. Additional research using identical image processing is needed.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Figure. From a representative glaucoma patient, right eye. (a) 4.5 and (b) 6.0 en face images of optic nerve head; 1mm wide annular quantification region of 4.5 (c) and 6.0 (d) scans.