Abstract
Purpose::
Development of advanced AMD follows formation of drusen and pigmentary changes of the RPE. Studies show that drusen are manifestations of local inflammatory events, and that captured cellular debris becomes the target for encapsulation by inflammatory mediators sequestered by the RPE and choroidal circulation. Drusen have variable fluorescence on fluorescein angiography which may indicate compositional changes, but this has not improved the ability to predict risk of AMD progression. Features of drusen and other sources of RPE elevation have been described using current imaging modalities, including time-domain optical coherence tomography (OCT). Spectral domain OCT (SDOCT), the latest form of OCT technology, allows for imaging of the macula at much higher resolution and speed than previously possible. Our primary objective is to characterize the SDOCT patterns of drusen and "drusenoid" pigment epithelial detachments in dry AMD utilizing a simple, reproducible, and descriptive methodology.
Methods::
In a prospective study of eyes with dry AMD, 100 SDOCT scans across a 10 X 10 mm area centered on the macula were obtained for each study eye. RPE elevation was characterized in terms of shape (convex or concave), height, width, reflectivity (relative to the photoreceptor layer and RPE), consistency (homogenous or heterogeneous pattern of reflectivity), and presence of either overlying hyperreflective spots or underlying shadowing.
Results::
In the 37 eyes studied, patterns of RPE elevation were categorized. Most were convex in shape with reflectivity less than the bordering RPE, but more than the photoreceptor layer. Although most had a homogeneous pattern of reflectivity, a large number of RPE elevations had distinct heterogeneous patterns of reflectivity. Categorizing reflectivity patterns of drusen with diameter less than 125 microns was difficult. Overlying hyperreflective spots were common in larger areas of RPE elevation and often matched sites of pigment clumping seen clinically.
Conclusions::
Novel drusen characteristics can be categorized from SDOCT imaging in this pilot study. SDOCT allows for more precise characterization of drusen and pigment epithelial detachment than previous imaging modalities. Longitudinal studies are needed to evaluate the potential for this categorization to better predict risk of disease progression.
Keywords: age-related macular degeneration • drusen • imaging/image analysis: clinical