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Novel noninvasive detection of the fovea avascular zone using confocal red-free imaging in diabetic retinopathy and retinal vein occlusion.

PURPOSE
To report confocal red-free imaging as a novel, noninvasive imaging modality for the detection of the foveal avascular zone (FAZ) and to compare its effectiveness to that of fluorescein angiography (FA) in diabetic retinopathy (DR) and retinal vein occlusion (RVO).


METHODS
This was a retrospective, observational, cross-sectional study. The authors enrolled 50 eyes with DR and 20 eyes with RVO. All subjects underwent confocal red-free imaging and FA using a scanning laser ophthalmoscope. For all subjects, the FAZ was identified on both confocal red-free and corresponding FA images and was delineated by two independent readers. The authors evaluated the concordance between the two imaging methods by comparing the sizes of the delineated areas and determining the overlapping ratio after image processing.


RESULTS
The image analysis showed a high correlation (r > 0.9) in the mean size of the FAZ between the red-free and corresponding FA images with DR or RVO. Reliable agreement between the two methods was confirmed by the comparison of size (P = 0.925 on independent t-test) and overlapping correspondence (overlapping ratio, 0.77) of the delineated area.


CONCLUSIONS
The findings suggest that confocal red-free imaging is a simple, reliable, safe, and noninvasive method for effectively imaging the FAZ. This procedure has the potential to be used for the noninvasive detection and quantification of FAZ in screening, initial evaluation, and follow-up observation of progressive ischemic retinopathies such as DR and RVO.