Abstract
Purpose :
To quantify the microvasculature changes in the macula in primary open angle glaucoma (POAG) patients as measured from optical coherence tomography angiography (OCTA) en face images of the ganglion cell-inner plexiform layer; and to determine the strength of correlation of perfusion with hemifield mean deviation values.
Methods :
6x6 mm2 scans of the macula were obtained on POAG and normal patients using the Angioplex spectral-domain OCTA, and Humphrey Visual Field 24-2 mean deviation (MD) defects were calculated for superior and inferior hemifields in each eye using proprietary formulas (Carl Zeiss Meditech; Dublin, CA). Prototype software was used: (1) to perform semi-automatic segmentation of the raw OCTA data to obtain a precise ganglion cell-inner plexiform layer (GC-IPL) en face image, and (2) to calculate perfusion parameters including vessel area density (VAD), vessel skeleton density (VSD), and vessel complexity index (VCI) for the macula (globally, hemifields, and other focal sectors) (Figure 1). Perfusion parameters in normal and glaucomatous eyes were compared using Wilcoxon rank sum test. Strength of correlation between each perfusion parameter and the corresponding hemifield MD values were calculated using Spearman’s rank correlation.
Results :
The study included 20 POAG eyes (12 mild/moderate [5 of which were preperimetric] and 8 severe) and 16 normal eyes. 6 eyes showed no visual field defects, 7 eyes had superior VF defects only, 2 eyes had inferior VF defects only, and 5 eyes had both. VAD, VSD, and VCI were significantly reduced with worsening severity of glaucoma (VAD P=0.0047; VCI P=0.0016; P= VSD 0.0023 using Kruskal-Wallis test). Glaucomatous eyes had significantly reduced perfusion parameters compared to normal eyes. There was a strong correlation between inferior HVF mean deviation and superior VAD (p= 0.0018), VSD (P= 0.000061), VCI (P= 0.000098) as well as globally (Figure 2).
Conclusions :
Glaucomatous eyes with a range of no (preperimetric) to severe visual field defects showed significant reduction in macular perfusion parameters as compared to normal eyes. There was a strong correlation of degree of perfusion impairment with degree of corresponding visual field defects in hemifields. This method will likely prove useful in the future for diagnosis, staging and monitoring of glaucoma.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.