The Association Between Drusen Extent and Foveolar Choroidal Blood Flow in Age-Related Macular Degeneration

Abstract

Purpose-To investigate the relationship between drusen extent and foveolar choroidal blood flow in non-exudative AMD.Methods-Total drusen area, average druse area, and total drusen number were determined using a computer program developed to quantify the extent of manually outlined drusen from fundus photographs of 157 patients (239 eyes) with non-exudative AMD. Laser Doppler flowmetry was used to assess relative choroidal blood velocity (ChB Vel ), volume (ChB Vol ), and flow (ChB Flow ) in the center of the fovea.Results-We found a significant inverse relationship between total drusen area and ChB Vol or ChB Flow . For every 1 mm 2 increase in total drusen area, ChB Vol decreased by 0.0061 arbitrary units (AU; p=0.03) and ChB Flow decreased by 0.23 AU (p=0.049). Average druse area was also significantly inversely related to ChB Vol and ChB Flow . For every 0.01 mm 2 increase in average druse area, the ChB Vol decreased by 0.0149 AU (p=0.001) and the ChB Flow decreased by 0.4951 AU (p=0.003). Adjustment for age weakened the significance, though it remained strong for average druse area versus ChB Flow (p=0.017) and ChB Vol (p=0.004). The computer-aided quantification of drusen used in this study showed high intra-and inter-grader agreement.Conclusion-In patients with non-exudative AMD, there is an association between increased drusen extent and decreased ChB Vol and ChB Flow . This suggests the presence of ischemia and possibly the reason why patients with high risk drusen are prone to advanced disease.

Optical Coherence Tomography–based Correlation Between Choroidal Thickness and Drusen Load in Dry Age-Related Macular Degeneration

“…24 Grunwald et al 24 hypothesized that this was in response to age-related decrease in density and diameter of the choriocapillaris that was previously observed by Ramrattan et al 25 A more recent study found an inverse relationship between choroidal blood flow (and volume) and drusen extent. 1 Another study also found that the eyes with the most drusen had the lowest choriocapillaris density. 26 It is not yet clear as to the reason for the inverse relationship.…”

“…26 It is not yet clear as to the reason for the inverse relationship. Berenberg et al 1 hypothesized that choroidal thinning may be because of drusen creating a distribution barrier to the trophic substances necessary for proper choriocapillaris maintenance. Inversely, they also hypothesized that thinner choroid and decreased blood flow result in decreased waste removal from the structures it supports, ultimately leading to drusen formation.…”

“…Therefore, it is the primary means of metabolic support for these tissues. 1 It has been shown that the choriocapillaris has unique features including high flow rate and low oxygen extraction that are mandatory to sustain normal photoreceptor metabolism. 3 Hence, the choroid's critical role of metabolic support for the retina and RPE suggests that this vascular layer may have a role in drusen development.…”

Smoking and choroidal thickness in patients over 65 with early-atrophic age-related macular degeneration and normals

“…1,[8][9][10][11][12][13]32 Therefore, choroidal thickness may be an additional useful clinical variable in assessing risk of AMD progression or the development of late AMD, particularly considering its apparent anatomic association with these two well-known risk factors. While a thin choroid is not necessarily related to blood flow or overall function, 50 there is evidence of regional choroidal blood flow alterations in AMD, [51][52][53][54][55] which may involve an overall decrease in blood flow and regional volume. 52,53,56 The present study is limited by small to moderate sample size, single-center study location, and predominantly Caucasian subjects.…”

Brain-Derived Neurotrophic Factor in Patients With Age-Related Macular Degeneration and Its Correlation With Retinal Layer Thicknesses

“…11 We found statistically significant difference in the BDNF concentration of AH and not in the serum of AMD group, confirming that BDNF is not only transported to the eye from the bloodstream, but is also produced in the eye. There might also be other possible explanations; First, the vascular supply might be reduced in eyes with AMD, 41 resulting in a decrease in levels of BDNF derived from serum. Second, Kliffen et al 42 found significant differences in the amount and composition of glycosaminoglycans (GAGs) between macula with and without AMD.…”