Abstract
Purpose :
Optical coherence tomography angiography (OCTA) provides high-resolution images of retinal vasculature whereby vessel density (VD) can be used as an outcome marker. VD is diminished in patients with retinitis pigmentosa (RP) but its quantification can be confounded by imaging artifacts. In this retrospective study, we investigate artifacts that may affect the clinical application of widefield OCTA (WF-OCTA) in patients with RP.
Methods :
University of Kentucky IRB (#48463) approved retrospective analysis of WF-OCTA images from 33 subjects with a diagnosis of RP and 12x12mm OCTA imaging (Plex Elite 9000, Zeiss, Dublin, CA). Images form the eye with higher signal strength and less artifacts were chosen. Images with a signal strength <7 or motion artifacts >6 and eyes with BCVA >20/200 were excluded. Raw images of the superficial capillary plexus were uploaded to FIJI (v2.0.0). Foveal-centered 9x9 and 6x6mm frames were outlined. Peripheral artifacts (PA) in 12x12, 9x9, and 6x6mm frames and motion artifacts (MA) in the 12x12mm frames were graded. PA prevalence rates were compared with Fisher’s exact test. Finally, the image area affected by PA was measured with FIJI tools.
Results :
Of the twenty-nine subjects who met inclusion criteria, 17 were female and 29 were Caucasian. The mean age was 46.5 ± 20.5 years (range, 8 to 74) and visual acuity 0.25 ± 0.23 logMAR units (-0.12 to 0.70). In 12x12mm frames, 27 (93%) images contained ≥1 artifact (PA or MA); 19 (65%) had ≥1 PA and 24 (83%) had ≥1 MA. Images with ≥1 PA decreased to n=10 (38%) and 5 (17%) in the 9x9 and 6x6 frames, respectively. The difference was significant between 12x12 and 6x6 images (p=0.002) but not between 12x12 and 9x9mm frames. The mean area of a PA was 12.5% ± 8.7 of an image. Finally, of the 24 (83%) 12x12mm images with ≥1 MA, 8 (28%) had 1-2 and 16 (55%) had >2 MAs; 5 (17%) had zero MAs. Of note, visual acuity range of the zero MA group was -0.1 to 0.4 logMAR units.
Conclusions :
Widefield OCTA images of RP eyes are prone to peripheral and motion artifacts which limit reproducible and repeatable vessel density measurements. Smaller field of imaging reduces peripheral artifacts and may be more valuable for following disease progression in patients with RP.
This is a 2020 Imaging in the Eye Conference abstract.