Association Between Drusen Extent and Foveolar Choroidal Blood Flow in AMD

Abstract

Purpose: : Previous studies have reported decreased choroidal blood volume and flow in age-related macular degeneration (AMD). These decreases are associated with progression of the disease. Drusen are also a risk factor for progression of AMD. The purpose of this study was to investigate the relationship between drusen extent and foveolar choroidal blood flow in subjects with non-exudative AMD.

Methods: : We used a computer program developed to quantify the extent of manually outlined drusen from digital fundus photographs. Total area of drusen, average druse area, and total drusen number within 3000µm of the center of the fovea were determined. Measurements were obtained from photographs of 157 patients (239 eyes) with non-exudative AMD and visual acuity of 20/40 or better. Laser Doppler flowmetry (LDF; Oculix instrument) was used to assess relative choroidal blood velocity (ChB_vel), volume (ChB_vol), and flow (ChB_flow) in the center of the fovea. Drusen quantification and LDF measurements were conducted in a masked fashion by two separate individuals. Linear regression analysis was used to assess the relationship between drusen extent and foveolar choroidal circulatory measurements.

Results: : The computer-aided quantification of drusen used in this study showed good grade-regrade agreement, with an intraclass correlation of 0.93 (0.84-0.97, 95% CI) for total area of drusen, 0.88 (0.73-0.95) for average druse area, and 0.91 (0.80-0.96) for total drusen number. In 239 study eyes, total area of drusen ranged from 0.001 to 9.62 mm² (median=1.65 mm²), average druse area ranged from 0.001 to 0.097 mm² (median=0.01 mm²), and total number of drusen ranged from 1 to 846 (median=126). We found a significant inverse relationship between total area of drusen and ChB_vol or ChB_flow. For every 1 mm² increase in total area of drusen, ChB_vol decreased by 0.0023 arbitrary units (AU; p=0.009) and ChB_flow decreased by 0.11 AU (p=0.007). Average druse area was also significantly inversely related to ChB_vol and ChB_flow. For every 1000 um² increase in average druse area, the ChB_vol decreased by 0.000008 AU (p=0.0001) and the ChB_flow decreased by 0.000289 AU (p=0.0003). Number of drusen was not significantly associated with choroidal circulatory measurements.

Conclusions: : In patients with non-exudative AMD, eyes with a larger extent of drusen, as measured by total area of drusen and average druse area, tend to have decreased ChB_vol and ChB_flow. These findings suggest a role for circulatory abnormalities in the development of drusen.

Keywords: age-related macular degeneration • blood supply