Abstract
PurposeTo study the ability of volumetric spectral domain optical coherence tomography (SD-OCT) to perform quantitative measurement of the choroidal vasculature in vivo.MethodsChoroidal vascular density and vessel size were quantified using en face choroidal scans from various depths below the retinal pigment epithelium (RPE) in 58 eyes of 58 patients with either epiretinal membranes (ERM), early age-related macular degeneration (AMD), or reticular pseudo-drusen (RPD). For each patient, we used the macular volume scan (6×6 mm cube) for vessel quantification, while high-definition (HD) cross-section raster scans were used to qualitatively assess vascularity of the choroidal sub-layers, and measure choroidal thickness.ResultsOf the 58 patients, more were female (66% versus 34% male), of whom 14 (24%) had ERM, 11 (19%) early AMD, and 33 (57%) RPD. Compared to intact choriocapillaris in all ERM (100%), none of the RPD and only 5/11 (45%) early AMD eyes had visible choriocapillaris on either cross section or C-scans (p-value<0.001). When comparing select regions from the most superficial C-scans, early AMD group had lowest vascular density and RPD had highest (p-value 0.04). Qualitative evaluation of C-scans from all three groups revealed a more granular appearance of the choriocapillaris in ERM versus increased stroma and larger vessels in the RPD eyes.ConclusionsSD-OCT can be used to qualitatively and quantitatively assess choroidal vascularity in vivo. Our findings correlate to previously reported histopathologic studies. Lack of choriocapillaris on HD cross-sections or C-scans in all RPD and about half of early AMD eyes suggests earlier choroidal involvement in AMD and specifically, RPD.
Highlights
The role of choroidal vasculature in the pathogenesis of agerelated macular degeneration (AMD) has been explored using various structural and functional approaches [1], [2], [3], [4], [5], [6], [7], [8]
A retrospective review of all patients diagnosed with AMD between June 2008 and July 2011 identified 58 patients between the ages of 41 and 97 who had undergone infrared (IR), fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (SD-OCT) imaging
Cscans taken just beneath the retinal pigment epithelium (RPE) in patients without evident choriocapillaris (100% of reticular pseudo-drusen (RPD) eyes and 55% of early AMD eyes), showed larger sized vascular channels more closely resembling the middle layer of control eyes (Figures 5, 6, 7)
Summary
The role of choroidal vasculature in the pathogenesis of agerelated macular degeneration (AMD) has been explored using various structural and functional approaches [1], [2], [3], [4], [5], [6], [7], [8]. The sensitivity of choroidal imaging in SD-OCT was improved through enhanced depth imaging [10], [11], [12], [13], [14], [15], [16], revealing that about one-third of patients with advanced AMD have thin choroid significantly below the mean thickness of age-matched controls [10], [11], [12], [13]. Choroidal thickness was found to be highly correlated with age, axial length, and refraction, emphasizing the importance of controlling for these variables when studying any patient population [16]. Choroidal thickness varies on a diurnal basis by as much as 29+/216 microns in one study, suggesting that it can be an highly variable measure of choroidal vasculature and further emphasizing the need to develop novel approaches to reliably assess choroidal vascular health in vivo [16], [17], [18]
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