Abstract
Purpose :
Optical coherence tomography angiography (OCTA) image quality is heavily influenced by the resolution of the scanning system optics. We conducted a clinical study to analyze the effects of increased optical resolution in the visualization of small retinal features.
Methods :
A PLEX® Elite 9000 swept-source OCTA system (ZEISS, Dublin, CA) was modified by incorporating a retractable lens into its optical path. The added lens reduced the OCT beam diameter at the retinal plane from 20µm to 12 µm. Ten normal eyes and ten eyes with retinal disease were recruited for this study. Each eye was imaged using two different OCTA scan patterns:
Pattern 1: a field of view (FOV) of 3x3mm, which captures 300 A-scans/B-scan (10µm sampling), and a total of 300 B-scans, each repeated 4 times (retractable lens out of optical path). The images acquired using Pattern 1 were cropped to match the FOV of Pattern 2
Pattern 2: FOV of 2.25x2.25mm, which captures 300 A-scans/B-scan (7.5µm sampling), and a total of 300 B-scans, each repeated 4 times.(retractable lens in optical path)
Results :
A total of 20 eyes were imaged with both methods in this study. In every case the angiographic appearance of small blood vessels and the overall quality of the enface image was superior when using higher optical and sampling resolution. Figure 1 shows the comparison between both configurations in one eye. Areas of prevalent small capillaries can be easily visualized (red circles) with higher resolution (Figure 1B), while the shape of the retinal networks is clouded by noise in the lower resolution scans (Figure 1A). B-scans obtained with Pattern 2 also showed smaller speckle noise (Figure 1D) when compared to those acquired with Pattern 1 (Figure 1C).
Conclusions :
Our study shows that increasing optical and sampling resolution provides improved visualization of finer capillaries by displaying more anatomically accurate vessel networks. Such improvement could prove valuable when assessing small abnormalities such as micro-aneurysms and vessel tortuosity, as well as provide more reliable vessel quantification.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.