Anterior Segment Angiography with 1050 nm Swept-Source Optical Coherence Tomography

Abstract

 

Purpose

 

To visualize anterior segment eye blood vessels with non-invasive, dyeless optical coherence tomography (OCT) angiography.

 

Methods

 

The ocular conjunctiva, sclera, and iris of human eyes were imaged in vivo using a swept-source anterior segment OCT system operating at 1050 nm wavelength and 100 kHz axial-scan repetition rate. Three-dimensional OCT angiography data was acquired over 6mm x 6mm and 9mm x 9mm regions with scan depth of 5 mm in tissue by using 3 repeated B-scans at 300 raster positions, each B-scan consisting of 300 axial-scans. Horizontal and vertical raster scan volumes were acquired and software motion correction was applied to reduce eye motion and combine the volumes. Split-spectrum amplitude-decorrelation angiography (SSADA) technique was used to detect flow and construct angiograms. En face angiograms were constructed by maximum flow projection.

 

Results

 

Anterior segment angiography was performed on 4 eyes (2 light-colored and 2 dark colored) of 4 normal subjects. Depth-resolved conjunctival, episcleral, and iris angiograms were generated for each eye. The OCT angiograms revealed a rich vascular system in conjunctiva and relatively sparse blood vessels in episclera (Figure 1). The iris angiogram exhibited radial iris vessel patterns in normal light-colored eyes (Figure 2). However, in dark iris the anterior pigment layer produced shadowing and flow artifacts that obscure deeper vasculature.

 

Conclusions

 

Depth-resolved anterior segment OCT angiography can visualize vascular patterns in conjunctiva, sclera and light-colored iris. It is potentially useful for the assessment of anterior eye vasculature. This is a first demonstration of OCT angiography in human iris and further studies are needed.  

 

Figure 1. En face cornea-scleral OCT structure image (left), bulbar conjunctival (middle) and episcleral (right) OCT angiograms of a human eye.

 

 

Figure 2. Iris OCT angiogram of a light-colored eye.