Extended field imaging using swept-source optical coherence tomography angiography in retinal vein occlusion

To evaluate the degree of ischemia in eyes with retinal vein occlusion (RVO) using swept-source optical coherence tomography angiography (SS-OCTA) with the extended field imaging (EFI) technique, which extends the area encompassed by SS-OCTA by scanning through trial frames fitted with a +20-diopter lens.

Retrospective observational study.

Twenty-three consecutive eyes of 22 patients with RVO underwent 12 × 12 mm SS-OCTA imaging both with and without EFI for determination of extension rate. Two graders blinded to the clinical data evaluated the degree of retinal ischemia in paired EFI-SS-OCTA and fluorescein angiography (FA) images, and the concordance rates between the grades were statistically examined.

One EFI-SS-OCTA image was not successfully obtained due to motion artifacts caused by the patient's poor central vision, while SS-OCTA images without EFI were captured in all 23 eyes. The average extension rate of EFI-SS-OCTA over SS-OCTA was 1.39 ± 0.06 and the average scanning area was enlarged by 76.4%. Two graders evaluated the degree of retinal ischemia by measuring nonperfusion areas as the sum of disc areas/diameters. Although their assessments of the EFI-SS-OCTA images were in complete agreement (Cohen's Unweighted Kappa coefficient = 1.00), concordance using FA images was only moderate (Cohen's Unweighted Kappa coefficient = 0.60).

EFI-SS-OCTA noninvasively produces wider field images of retinal vasculature with one capture and provides resolution sufficient to accurately evaluate retinal capillary nonperfusion in RVO.