Three–Dimensional High Resolution Optical Coherence Tomography of Progressive Changes in Age–Related Macular Degeneration

Abstract

Purpose: : To document the progression of degenerative macular disease from early to advanced stages at all macular locations using three–dimensional high–resolution optical coherence tomography (HR–OCT).

Methods: : Three–dimensional retinal imaging is performed using a second generation frequency domain HR–OCT system with an axial resolution of 6 µm and up to 20 k A–scans/second resulting in 256x256x1024 or 128x512x1024 voxels per volume. Raster scanning of an approximately 5.8 by 5.8 mm wide field within 2 mm depth range was performed to cover the complete macular region in full detail. Tomograms were correlated with the conventional radial scanning technique consisting of only 6 crossectional scans (at 768x1024 pixel each) and extrapolation for missing sites.

Results: : In early disease, drusen are detected at their specific location. Small drusen appear as localized detachments of the RPE with intact layered architecture of the photoreceptor segments. In large drusen RPE elevation and decomposition is associated with an annihilated photoreceptor band. In occult choroidal neovascularization (CNV), significant destruction of the RPE–outer segment layer is seen with fluid pooling in the subretinal space. However, the disintegrity of the outer retinal layers is most prominent and abundant in occult lesions. Classic CNV is delineated in three dimensions and is associated with extensive extravasation intra– and subretinally.

Conclusions: : Three–dimensional high resolution OCT allows to identify pathognomonic changes during the progression of age–related macular degeneration. One benefit is the high resolution in imaging histological changes such as RPE and photoreceptor alteration. The second advantage is the ability to investigate all locations and to quantify fluid volume and extension precisely with a single measurement.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • macula/fovea • age-related macular degeneration