Purpose
To perform feasibility study using 27kHz Zeiss Cirrus-4000 HD-OCT based prototype system to generate retinal microvascular maps in subjects with diabetic retinopathy (DR)
Methods
27 kHz Cirrus OCT based prototype system (Carl Zeiss Meditec, Dublin, CA) is used to generate retinal microvascular maps in human subjects by the use of optical micro-angiography (OMAG) algorithms. The OCT system has a tracking feature that minimizes motion artifacts induced by eye motion. To produce microvascular images from 3D dataset, we developed a method of phase compensation to further reduce the motion artifacts that is necessary to provide high quality capillary perfusion maps of the retina. We also developed a segmentation algorithm to separate microvasculature within landmarked physiological depth layers of retina as well as within choroid. The layers include nerve fiber layer + ganglion cell layer (NFL+GCL), inner plexiform layer (IPL), and outer plexiform layer (OPL). To assess the feasibility, we used the 3D datasets scanned from 5 subjects diagnosed with DR (n = 10 eyes). For one subject, clinical fluorescein angiography (FA) images were acquired on the same day as the OCT scan and compared with the resulting en-face OMAG images
Results
Retinal OMAG images generated from Cirrus-4000 system showed clearer microvascular maps compared to FA images. In addition, OMAG provides depth-resolved retinal microvascular networks organized within three landmarked physiological layers. The microvascular features of typical DR observed include microaneurysms, capillary non-perfusion, and dilated or tortuous vessels. The results also demonstrated the ability of the Cirrus OCT system to distinguish different forms of the microaneurysms, such as saccular, fusiform and focal bulges. Most of the microaneurysms were observed in the deeper depth of inner retinal capillary plexus, originating from the locations between IPL and OPL. Tortuous vessels were also observed near fovea, which is a significant feature of DR. Fig.1 gives an example of OMAG description of irregular enlargement of the foveal avascular zone, consistent with mild diabetic macular ischemia, comparing with the corresponding FA image
Conclusions
Zeiss Cirrus OCT based prototype system demonstrated capability to generate retinal OMAG microvascular maps that can be valuable to aid in the diagnosis and therapeutic invention of DR
Keywords: 499 diabetic retinopathy •
550 imaging/image analysis: clinical •
552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)