Abstract
Purpose: :
Capillary microaneurysms are a clinicopathological hallmark of early diabetic retinopathiy. Beside ophthalmoscopy,, fluorescein angiography (FA) is the golden standard examination technique for tracing these retinal alterations. The aim of this study was to evaluate the role of high definition optical coherence tomography (HD-OCT) in detecting microaneurysms (MAs) in early diabetic retinopathy.
Methods: :
20 patients with early diabetic retinopathy showing diabetic MAs without clinically significant macular edema were examined using FA (HRA 2; Heidelberg Engeneering) and HD OCT (Carl Zeiss Meditec, resolution 4096 x 1024 and 512 x 128 pixel / 5.8 x 5.8 mm) during a same day examination.Results were correlated in order to visualize MAs in OCT raster scans as seen in FA.
Results: :
The OCT technique allowed to identify MAs not visible during clinical examination. Creating a slab of each patient‘s en face OCT image located in the outer retinal layers, characteristic shadowing phenomena caused by MAs could be detected. These shadowing phenomena seemed to be caused by blood accumulated in MAs, which cannot be penetrated by the OCT beams. Even if the HD OCT resolution was not high enough to clearly visualize MAs themselves, in all eyes it was possible to image their OCT beam shadows in the corresponding en face OCT images.
Conclusions: :
HD OCT allows clear detection of MAs secondary to diabetic retinopathy otherwise not recognizable clinically. The observed laser beam shadowing obviously caused by the characteristic blood accumulation in diabetic MAs could be used to develop new algorithms for an automated detection of MAs based on the OCT technique. This offers the perspective to use this non invasive imaging technique instead of angiography for DME staging and screening examinations.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • diabetic retinopathy • retina