Diabetic Macular Ischemia Diagnosis: Comparison between Optical Coherence Tomography Angiography and Fluorescein Angiography

Abstract

Purpose. To compare fluorescein angiography (FA) and optical coherence tomography angiography (OCTA) images of foveal avascular zone (FAZ) in patients with diabetic retinopathy (DR) with and without diabetic macular ischemia (DMI). Methods. The Wilcoxon signed-rank test was used to compare area measurements and p values of <0.05 were considered statistically significant. FA and OCTA images were independently graded by 2 observers that reached agreement regarding quantitative DMI according established protocols. The ischemic area was divided into "large" macular ischemia (superior to 0.32 mm²) and "small" (inferior to 0.32 mm²) groups. Quantitative analyses of the FAZ were performed using custom software. Results. Thirty-four eyes from 34 diabetic patients were enrolled. Subjects with DMI presented a mean area on FA and OCTA of 0.68 ± 0.53 mm² and 0.58 ± 0.35 mm², respectively (p = 0.1374). Patients without DMI presented a mean area on FA and OCTA of 0.19 ± 0.67 mm² and 0.20 ± 0.79 mm², respectively (p = 0.9594). The ICC for the FAZ measurements between the 2 observers on FA and OCTA was 0.96 and 0.92, respectively. Conclusion. OCTA represents a novel technique for the diagnosis of DMI and it may become an alternative to FA for this purpose.

Figure 1

Box plots demonstrating foveal avascular zone (FAZ) area measurements on fluorescein angiography (FA) versus optical coherence tomography angiography (OCTA). Box blots demonstrate results according foveal avascular zone area on fluorescein angiography and optical coherence tomography angiography in patients with and without diabetic macular ischemia (DMI). Circles represent outliers.

Figure 2

Diabetic macular ischemia (DMI) as seen on fluorescein angiography (FA) versus optical coherence tomography angiography (OCTA). Multimodal imaging of three different patients. Evaluation of foveal avascular zone (FAZ) extent on fluorescein angiography (a, b, and c) compared to optical coherence tomography (OCT) angiography. (d, e, and f) FAZ areas on both methods are represented by colored dotted lines. (g, h, and i) Semiautomatic segmentation of correspondent SD-OCT B-scan.

Figure 3

Quantifying foveal avascular zone (FAZ) area morphology on fluorescein angiography (FA) versus optical coherence tomography angiography (OCTA). Multimodal imaging of a left eye with central nonperfusion. (a) Yellow dotted lines delimits foveal avascular zone (FAZ) area on fluorescein angiography (FA) at 0:34 min. (b) Red dotted lines representing the FAZ area on optical coherence tomography angiography (OCTA) angiogram segmented at the level of the superficial retinal vasculature. (c) An overlap of FAZ areas obtained on FA and OCTA was performed, displaying similarity between the 2 measurements. To obtain centered images, a seed point at the center was used. To delimit FAZ areas in this specific case, the edge points were manually selected along the borders of the vessels, ignoring nearby capillary dropout region.