Enface OCT Angiography (OCTA) Techniques for Enhanced Visualization of Choroidal Neovascularization

Abstract

 

Purpose

 

OCTA is a promising non-invasive imaging technique that may be used for detecting and monitoring vascular abnormalities such as choroidal neovascularization (CNV). The goal of this study is to demonstrate that CNV can be detected using OCTA on a spectral-domain OCT system. Furthermore, new OCTA visualization tools are used that provide 3D impressions in 2D enface projections to better assess the extent of neovascularization growth.

 

Methods

 

Cirrus 5000 HD-OCT based prototype system (Carl Zeiss Meditec Inc., Dublin, CA) was used to obtain OCTA scans at 67.5 kHz. OCT microangiography (OMAG) technique with 2D cross-correlation based motion correction was used to obtain OCTA results. Line scanning ophthalmoscope (LSO) based tracking was used to minimize motion artifacts. Three subjects diagnosed with CNV were included in the study. Color fundus (CF) images and fluorescein angiograms (FA) were also obtained and used for correlating the results of OCTA images. Depth-encoded OCTA color maps were generated to better appreciate the depth information as well as to delineate the CNV growth. For depth-encoded color maps, vasculature in the inner-retina, mid-retina and outer-retina were encoded in the red, green and blue color, respectively.

 

Results

 

CNV was well visualized by OMAG technique and the results correlated well with the CF and FA images. Figure 1 shows the foveal region of 3mm x 3mm from the CF and FA image and the corresponding OMAG images of the left eye for a 70 year old female subject with CNV. While, the inner-retina vasculature (superficial retinal capillary plexus) looks relatively normal (1C), CNV region is well delineated and emphasized with the blue color in the depth-encoded color map (1D). CNV region in OCTA images corresponds well with the pathology shown in FA and CF images.

 

Conclusions

 

Cirrus based SD-OCT prototype system demonstrated fine spatial resolution of the CNV complex. In addition, OCT angiography maps can provide detailed depth encoded information of retinal vasculature that is not possible with traditional FA.  

 

Fig. 1 Imaging CNV. A) CF image. B) FA image. C) OCTAimage of inner-retina vasculature. D). Depth-encoded color OCTA color map where the growth of CNV membrane is emphasized in the blue color and corresponds well with FA image (dashed yellow circles).

 

 

Fig. 2 B-scan (right) corresponding to the line across the CNV growth as shown in OCTA enface image (left).