Imaging Artifacts and Segmentation Errors With Wide-Field Swept-Source Optical Coherence Tomography Angiography in Diabetic Retinopathy

Abstract

Purpose: To analyze imaging artifacts and segmentation errors with wide-field swept-source optical coherence tomography angiography (SS-OCTA) in diabetic retinopathy (DR).

Methods: We conducted a prospective, observational study at Massachusetts Eye and Ear from December 2018 to March 2019. Proliferative diabetic retinopathy (PDR), nonproliferative diabetic retinopathy (NPDR), diabetic patients with no diabetic retinopathy (DR), and healthy control eyes were included. All patients were imaged with a SS-OCTA and the Montage Angio (15 × 9 mm) was used for analysis. Images were independently evaluated by two graders using the motion artifact score (MAS). All statistical analyses were performed using SPSS 25.0 and R software.

Results: One hundred thirty-six eyes in 98 participants with the montage image were included in the study. Patients with more severe stages of DR had higher MAS by trend test analysis (P < 0.05). The occurrence of segmentation error was 0% in the healthy group, 10.53% in the no DR group, 10.00% in the NPDR group, and 50% in the PDR group. Multivariate regression analysis showed that the severity of DR and dry eye were the major factors affecting MAS (P < 0.05). There were some modifiable artifacts that could be corrected to improve image quality.

Conclusions: Wide field SS-OCTA assesses retinal microvascular changes by noninvasive techniques, yet distinguishing real alterations from artifacts is paramount to accurate interpretations. DR severity and dry eye correlated with MAS.

Translational relevance: Understanding contributing factors and methods to reduce artifacts is critical to routine use and clinical trial with wide-field SS-OCTA.

Keywords: artifact; diabetic retinopathy; optical coherence tomography angiography; segmentation error; wide field.

Figure 1

Representative images for MAS Grading. (A) MAS 1 with no obvious artifacts. (B) MAS 3 with significant displacement (arrow head) and nonsignificant black lines (narrow arrow) in one quadrant. (C) MAS 4 with significant displacement (arrow head) and vessel doubling (*) in two quadrants, no significant black lines. (D) MAS 5 with significant black lines (wide arrow) in one quadrant.

Figure 2

Alignment error. Both retinal-depth encoded (A, C) and DCP (B, D) montage images before (A, B) and after projection removal (C, D) are shown here. After projection removal, the upper and lower part of retinal-depth encoded montage image (C) appeared to be of different depth, which was defined as “alignment error.”

Figure 3

Representative OCTA images. Retinal-depth encoded (A, B), SCP (C, D), representative B scan showing segmentation error due to NV (E, F) for follow-ups of a PDR patient. The patient first presented with blurry vision 1 month after panretinal photocoagulation (A, C, E) and experienced significant progression at 1-month follow-up (B, D, F). The images at follow-up were taken with small pupil and had more artifacts compared with the first visit.

Figure 4

Representative OCTA images before (A) and after (B) head position adjustment. Once the chin or the forehead is not adhered to the machine, the image (A) will lose signal in the periphery and show artifacts. After head position adjustment, the image (B) was free of artifacts.