Three–Dimensional Imaging of Fluid and Edema in Retinal Disease Using High Resolution Optical Coherence Tomography

Abstract

Purpose: : Conventional optical coherence tomography systems offer a limited number of retinal scans, making it difficult to track the stage and progression of exudative disease in its full extension. State of the art three–dimensional high resolution optical coherence tomography is based on high speed raster scanning and was used to visualize location and volume of intra–, subretinal and sub–pigment–epithelial (RPE) fluid.

Methods: : 80 eyes of 80 patients with different stages and distribution of pathologic fluid accumulation were imaged using a high–speed frequency–domain high–resolution optical coherence tomography device with an axial image resolution of 6 µm and up to 20 k A–scans/second resulting in 256x256x1024 or 128x512x1024 voxels per volume. A volume of 5.8x5.8 mm and a depth–range of 2 mm was examined in the macular retina. Two–dimensional quasi–histologic section analysis as well as a three–dimensional reconstruction was performed.

Results: : Detailed information about layer–specific distribution of fluid accumulation can be obtained in all compartments, i.e. intra–, subretinally and sub–RPE. Intraretinal fluid occurs as non–cystic or in the majority of cases, cystic edema, mostly within the outer nuclear/plexiform layers. Subretinal fluid appears as a dome–shaped, well demarcated fluid pooling and is often associated with a loss of photoreceptor layer integrity. Sub–RPE fluid is pathognomonic for choroidal disease and appears with high prominence and steep borders. The regression of intra– and subretinal edema before and following antiangiogenic or photodynamic therapy is documented with its realistical volume and with all locations measured. Fluid–associated structural changes within each layer of the neural retina are clearly identified. Particularly a destruction of the photoreceptor layer is highlighted.

Conclusions: : High–speed frequency–domain high–resolution optical coherence tomography provides extensive information regarding precise location and objective volume of pathologic fluid. Volumetric quantification of fluid becomes accessible as well as an identification of related structural changes of the neural architecture. Three–dimensional OCT significantly improves the clinical evaluation, monitoring of disease progression and analysis of treatment benefit.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • macula/fovea • choroid: neovascularization