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M. Bolz, C. Ahlers, M. Ritter, M. Schneider, W. Geitzenauer, C. Hirn, U. M. Schmidt-Erfurth; Correlation of Fluorescein Angiography and High Resolution OCT in Diabetic Macular Edema. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3444.
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© ARVO (1962-2015); The Authors (2016-present)
Fluorescein angiography (FA) and optical coherence tomography (OCT) are important imaging tools in the diagnosis of diabetic macular edema. High definition OCT (HD OCT) not only has the advantage of assessing retinal morphology with a significant higher resolution, but also of performing 128 scans in a raster pattern in a given retinal area instead of 6 radial scans like OCT 3. Aim of this study was to correlate FA and HR OCT findings in diabetic macular edema.
Fifteen patients with a diabetic macular edema were examined using FA (HRA 2; Heidelberg Engineering) and HD OCT (Carl Zeiss Meditec, resolution 4096x1024 and 512x128pixel/ 5.8x5.8mm) on the same day. With the help of Adobe Photoshop, a grid containing 15x7 fields was superimposed on the HD OCT enface image. According to retinal structures, the dimension of the enface HD OCT image combined with the superimposed grid was adjusted to the late-phase FA image. By digitally substracting the enface image, the grid was found in the same position in the FA image as in the original enface image of HD OCT. This allowed for detailed comparative analysis of vascular leakage in FA and retinal morphological changes in HD OCT.
In the fovea, a pettaloid hyperfluorescence pattern was caused by large cystic spaces located in all retinal layers as observed by HD OCT. A honeycomb pattern hyperfluorescence, which was found parafovealy in FA was correlated to the presence of cystic spaces and swelling in the outer nuclear (ONL), the outer plexiform (OPL) and the inner nuclear layer (INL) (p<0.05). The retinal areas affected by these alterations were found to be bigger in HD OCT than in FA. Diffuse leakage in FA could be correlated to a swelling in ONL, OPL and INL. In HD OCT, a swelling of ONL could be found even if there was no or only slight diffuse hyperfluorescence in FA. Hyperreflective structures, such as hard exudates, could clearly be identified in the central retinal layers and near to microaneurysms. All types of morphologic alteration, such as swelling, cystic spaces or hard exudates, were not confined to one single retinal layer.
Late-phase FA images and enface HD OCT images can be correlated directly showing the high coherency between vascular leakage and morphologic retinal changes. Cystic spaces -causing honeycomb hyperfluorescence - and retinal swelling - causing diffuse hyperfluorescence - can mainly be observed in ONL, OPL and INL. Because of its raster scan pattern, HD OCT proved to be the first OCT generation appropriate for direct correlation with FA.
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