Ocular Blood Flow Assessment in AMD and its Potential Clinical Applications

Abstract

Abstract: : Purpose: To summarize our findings regarding ocular circulation changes in age-related macular degeneration (AMD), found in retrobulbar and choroidal vascular beds, and to explain the potential clinical applications in assessing different AMD treatments. Methods: All procedures were aapproved by an IRB, and informed consent obtained. In two studies combined, we evaluated the ocular hemodynamics of 46 non-neovascular AMD and 46 age-matched controls. In one we evaluated the retrobulbar circulation and in the other the choroidal circulation. In a third study we evaluated the effects of transpupillary termotherapy (TTT) given to 11 AMD subjects for occult choroidal neovascularization (CNV) on the retrobulbar circulation. Results: Non-neovascular AMD subjects showed a consistent trend toward lower peak systolic velocities (PSV) and end-diastolic velocities (EDV) in the posterior ciliary arteries (PCA) and central retinal arteries (CRA), as compared to age-matched control. Especially, in the nasal PCA, mean EDV was 26% lower than control (P =.0012). The CRA resistive index (RI, a measure of peripheral vascular resistance) was significantly higher in AMD patients. In the choroid, non-neovascular AMD subjects found to have prolonged perifoveal mean filling times and more heterogeneity between regions of the filling times within the same eyes, as compared to controls, suggesting choroidal perfusion deficits. TTT for occult subfoveal CNV resulted in an acute and significant decrease of CRA PSV (16%, P = 0.0137) and EDV (21%, P = 0.0222) 1-day post-treatment, and a significant decrease in nasal PCA EDV (36%, P = 0.0105) at 1 month post-treatment. Conclusions: These studies, as well as of others, indicate that AMD may be related to regional ocular ischemia. Different systemic treatments, such as medications for hypertension, as well as ocular AMD treatments, such as photodynamic therapy and rheopheresis, may effect the ocular circulation. With current technology, the assessment of these treatments’ effects on the ocular circulation is feasible.

Keywords: age-related macular degeneration • blood supply • retina