Optical coherence tomography angiography for macular microvessels in ischemic branch retinal vein occlusion treated with conbercept: predictive factors for the prognosis

Abstract

Aim: To evaluate the predicative factors of visual prognosis using optical coherence tomography angiography (OCTA) in ischemic branch retinal vein occlusion (BRVO) patients with macular edema (ME) after anti-vascular endothelial growth factor (VEGF) treatment.

Methods: In this retrospective analysis, data from 60 patients (60 eyes) with a definite diagnosis of ischemic BRVO with ME by fundus fluorescein angiography (FFA) were studied. The eyes with ME according to spectral domain optical coherence tomography (SD-OCT) underwent intravitreal conbercept (IVC) and 3+pro re nata (PRN) regimen. The injection times were recorded. Two weeks after injection, fundus laser photocoagulation was performed in the non-perfusion area of the retina. The patients were followed up once a month for 6mo. The best-corrected visual acuity (BCVA), foveal avascular zone (FAZ), and A-circularity index (AI), at 6mo and the baseline were compared.

Results: All patients showed significant improvement in BCVA from 0.82±0.32 to 0.39±0.11 logMAR (P<0.001). The mean central macular thickness (CMT) significantly decreased from 476.22±163.54 to 298.66±109.23 µm. Both the FAZ area and AI at 6mo were significantly higher than those at the baseline: the FAZ area increased (0.38±0.02 vs 0.39±0.02 mm², P<0.05); the AI increased (1.27±0.02 vs 1.31±0.01, P=0.000). The baseline BCVA showed a significantly positive correlation with the baseline FAZ area, FAZ perimeter (PERIM) and AI, final visual gain (FVG) and injection times, respectively (P<0.001). FVG showed a significantly negative correlation with the FAZ area, PERIM, AI and injection times, but a significantly positive correlation with vessel densities (VDs) 300 µm area around FAZ (FD-300; P<0.001). Injection times was positively correlated with the baseline FAZ area, and AI, but inversely correlated with the baseline FD-300 (P<0.001). However macular ischemia was noted in 5 cases during follow-up.

Conclusion: Using OCTA to observe macular ischemia and quantify parameters can better predict the final visual prognosis of patients before treatment. The changes in FAZ parameters may influence the visual prognosis and injection times.

Keywords: branch retinal vein occlusion; conbercept; foveal avascular zone; macular edema; optical coherence tomography angiography.

Figure 1. OCTA images of BRVO patients with macular ischemia presents as the broken foveal capillary ring (red arrow) to different extent

OCTA: Optical coherence tomography angiography; BRVO: Branch retinal vein occlusion.

Figure 2. Macula ischemia varies considerably in size of NPA in BRVO on OCTA

A: Mild macular ischemia had scattered tiny NPA around macular NPA with a capillary plexus around the entire circumference. B and C: The enlargement of NPA (red arrow). NPA: Nonperfusion area; BRVO: Branch retinal vein occlusion; OCTA: Optical coherence tomography angiography.

Figure 3. Ischemic BRVO with ME in a 55-year-old woman was first seen in 2021 (Case 1)

The patient had a total of 3 times of IVC injections, the first injection at 2021-10-18, the second one at 2021-11-18, and the last one at 2022-01-03. During the follow-up, the BCVA increased from 0.6 to 0.2. FAZ area increased from 0.452 to 0.626 mm². PERIM increased from 2.752 to 3.566 mm. AI increased from 1.16 to 1.27. FD-300 (%) increased from 51.40 to 49.42. B-scan showed the ME from onset to regression. BRVO: Branch retinal vein occlusion; ME: Macular edema; FAZ: Foveal avascular zone; IVC: Intravitreal conbercept; BCVA: Best-corrected visual acuity; FD-300: Vessel densities 300 µm area around FAZ; PERIM: Foveal avascular zone perimeter; AI: A-circularity index.

Figure 4. Heat map of correlation between the baseline BCVA and FAZ parameters

The baseline BCVA had significantly positive correlation with FAZ area, PERIM and AI, but negative correlation with FD-300. BCVA: Best-corrected visual acuity; FAZ: Foveal avascular zone; FD-300: Vessel densities 300 µm area around FAZ; PERIM: Foveal avascular zone perimeter; AI: A-circularity index.

Figure 5. Heat map of correlations among FVG and other variables

FVG was positively related to age and FD-300, but strongly and inversely related with baseline BCVA, FAZ area, PERIM, AI, and the number of injections. FVG: Final visual gain; FD-300: Vessel densities 300 µm area around FAZ; BCVA: Best-corrected visual acuity; FAZ: Foveal avascular zone; PERIM: Foveal avascular zone perimeter; AI: A-circularity index.

Figure 6. The OCTA images of the macular area of the two BRVO eyes

A and C: At baseline, basically complete continuity of the arch ring was showed; B and D: At 6mo, the vascular continuity of the arch ring was disrupted, and macular ischemia developed (red arrow). OCTA: Optical coherence tomography angiography; BRVO: Branch retinal vein occlusion.