Power of OCT-A (Optical Coherence Tomography Angiography) in Glaucoma

PURPOSE/RELEVANCE: OCT-A is a new non-invasive, motion contrast micro-vascular imaging modality. Using OCT-A, we analyzed vessel density measurements and structural properties in controls, glaucoma suspects and patients with mild, moderate and severe glaucoma. METHODS: In an IRB approved retrospective study, 69 controls, 36 glaucoma suspects, 54 mild glaucoma, 25 moderate glaucoma, and 12 severe glaucoma patients were studied. One eye was randomly selected per patient. Collected data included: age, race, gender, family history of glaucoma, CCT, IOP, visual field (VF) MD and PSD, cup/disc ratio (C/D), and OCT-A scanning parameters: global and sectoral optic nerve fiber thickness, ganglion cell complex thickness, disc vessel densities, retinal vessel densities, and the foveal avascular zone area. A Jonckheere-Terpstra, chi-square, independent t-test, and correlation matrix were used to determine differences between controls and glaucoma groups. RESULTS: Optic disc and retinal vessel densities showed a significant decrease as the glaucoma progressed, from mild to severe form, 52.9% to 43.1% and 48.1% to 43.4%, respectively (p<0.01). Nerve fiber layer thickness decreased from 83.0μm to 60.1μm, respectively (p<0.01). Both structural properties and vessel densities were effective at determining glaucoma stage, but neither variable was superior to the other (p=0.21). Between controls and glaucoma suspects, we noticed structural property differences, but not vessel density differences (p≤0.05). DISCUSSION: The vessel densities and structural properties from OCT-A have a significant decreasing trend as glaucoma progresses and they support the clinical diagnosis of glaucoma based on VF damage. However, in glaucoma suspects, the structural properties were reduced compared to controls, while vessel densities remained unchanged. This could suggest that structural damage may occur before vessel damage in glaucoma suspects when there is no VF defect. CONCLUSION: Optic disc and retinal vessel densities and structural properties assessed by OCT-A can provide an objective measure of glaucoma damage in the eye. Our study has shown that structural damage may occur before vessel density damage in glaucoma suspects.