Choroidal neovascularization imaging using multiple en face optical coherence tomography angiography image averaging.

PURPOSE: To determine the effects of averaging five en face optical coherence tomography angiographic (OCTA) images on the quality of the images in eyes with a choroidal neovascularization (CNV). METHODS: Twenty-seven eyes of 25 patients (18 men, 7 women; average age 71.0 years) with a CNV were examined by OCTA (OCT HS-100, Canon. Japan). A 3 × 3-mm image including the CNV was recorded and automatically segmented between the retinal outer layers. Analyses were performed on a single image (S-image) and the average of five single images of the same area (A-images). The region of the CNV was selected by ImageJ, and the peak signal-to-noise ratio (PSNR), the vascular density (VD), fractal dimension (FD), and the noise component using band pass filter (BPF) processing of the S- and A-images of each case were compared. RESULTS: The average PSNR for the A-images was 14.0 which was significantly higher than the 12.2 for the S-images (P < 0.01). However, the average VD was 33.6% for the S-images and 34.8% for the A-images (P > 0.1). The average FD was 1.67 for the S-images and 1.54 for the A-images (P < 0.01). The mean luminance difference obtained by subtracting the luminance of the A-image from the S-image after BPF processing was 10.41 ± 14.66 db which was positive for all eyes. CONCLUSIONS: The better quality of the A-images of a CNV and absence of a significant difference in the vascular density indicates that the improvement was due to the removal of the same signal levels of the noise component and blood vessels.

Correlation between reduction in macular vessel density and frequency of intravitreal ranibizumab for macular oedema in eyes with branch retinal vein occlusion.

AIM: To determine whether there is a significant correlation between the reduction in macular vessel density and the recurrence of macular oedema in eyes with branch retinal vein occlusion (BRVO). METHODS: We reviewed the medical records of 27 eyes with macular oedema associated with BRVO. All eyes had received pro re nata intravitreal ranibizumab (IVR) injection. A reinjection of ranibizumab was performed when the central foveal thickness was ≥300 µm. At 12 months, patients without additional IVR for the last 4 months were placed in the resolved group, otherwise they were placed in the recurrence group. The macular vessel density in 3×3 mm area centred on the fovea was determined by optical coherence tomography angiography. RESULTS: At 12 months, 11 of the 27 (40.7%) eyes were placed in the resolved group and the other 16 (59.3%) eyes were placed in the recurrence group. The mean macular vessel density reduction in the resolved group was 17.60%±7.88% and that in the recurrence group was 8.12%±7.48% (P=0.0042). The mean number of IVR injections in the resolved group was 2.1±1.1 and that in the recurrence group was 5.1±1.2 (P<0.0001). In all eyes, multivariate analysis showed that the reduction in macular vessel density was significantly and negatively correlated with the number of IVR injections (ß=-0.6746, P=0.0028). CONCLUSIONS: A reduction in the macular vessel density was significantly correlated with the number of recurrences of macular oedema associated with BRVO.