Optical Coherence Tomography Angiography of the Peripapillary Retina in Glaucoma

Abstract

Glaucoma is the second leading cause of blindness worldwide, affecting more than 60 million people and predicted by 2020 to reach 79.6 million.^1-3 Early diagnosis and close monitoring of glaucoma are important given the insidious onset of glaucoma, with irreversible nerve damage associated with vision loss. Visual field (VF) testing remains the criterion standard for glaucoma assessment, but it has substantial variability, with poor reproducibility in some patients.^4,5 Structural studies^6-14 of retinal nerve fiber layer (NFL) by optical coherence tomography (OCT) show its promise as an objective quantifiable measure for glaucoma assessment, but it has limited sensitivity for detecting early glaucoma and only moderate correlation with VF loss. Some studies^15-21 have shown that glaucoma may be associated with vascular dysfunction, suggesting another possible imaging target for early diagnosis and monitoring of glaucoma. Laser Doppler flowmetry (LDF) and laser speckle flowgraphy (LSFG) have demonstrated reduced optic nerve head (ONH) and peripapillary blood flow dynamics in glaucoma.^20,22-27 Jia et al¹⁸ recently quantified optic disc perfusion using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm on a custom swept-source OCT system and showed decreased optic disc perfusion in glaucoma. To our knowledge, no attempt has been made to evaluate the peripapillary retinal vasculature using OCT in glaucomatous eyes. For this study, we obtained OCT angiograms of the peripapillary retina on a commercially available spectral OCT system and quantified peripapillary flow index and peripapillary vessel density using the SSADA algorithm. We compared the perfusion indexes between normal and glaucomatous eyes. Correlation of these perfusion indexes with more conventional measures of glaucoma (VF and structural OCT) was also investigated.