Abstract

DO.13.08

Evaluation of lesion size in active choroidal neovascularization using high resolution optical coherence tomography

Golbaz I., Ahlers C., Simader C., Geitzenauer W., Ritter M., Prünte C., Schmidt-Erfurth U.
Department of Ophthalmology, Medical University of Vienna

Objective: Lesion size in fluorescein angiography (FA) has been used as a criterion in various clinical trials. However, this parameter is often difficult to define due to staining or blockade phenomena. Conventional optical coherence tomography (OCT) could not resolve this problem due to the techniques limited ability to provide realistic volumetric information or three-dimensional maps. High resolution optical coherence tomography (HR-OCT) enables for new parameters. This study introduces and evaluates the parameter lesion size, determined by using fast raster scanning HR-OCT and fluorescein angiography (FA).
Methods: 15 eyes with active choroidal neovascularization (CNV) were imaged using a frequency domain HR-OCT system (Cirrus^® Prototype) with an axial resolution of 6 µm and 20 k A-scans/second resulting in a 6x6x2 mm³ retinal volume. Lesion size measurement and topographic reconstructions were performed using semiautomatic segmentation software. FA was carried out using the Heidelberg retina angiography system (HRA2, Heidelberg Engineering). In FA lesion size was measured using standard HRA2 software.
Results: The lesions different compartments e.g. subretinal fluid (SRF), pigment epithelial detachments (PED) and retinal thickening can be measured accurately using semiautomatic segmentation in all cases. Basis of the lesion can be differentiated into its parts using false colour illustrations. Comparing these images to angiograms, HR-OCT allows for clear differentiation between PED and subretinal fluid, which cannot be observed in FA.
Conclusions: Unlike FA, HR-OCT imaging of a lesion's basis allows for detailed evaluation regarding SRF and PED borders in occult CNV. Ratios between different areas of affected retinal tissue can exactly be calculated and evaluated. HR-OCT enables for direct comparison of scanned retinal tissue to FA images. This might enhance the understanding of characteristic findings in both, FA and HR-OCT.

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