Purpose: We compared the area of the foveal avascular zone (FAZ) and macular capillary network density at different retinal layers using swept-source optical coherence tomography angiography (OCT-A) in normal individuals and patients with diabetic retinopathy (DR). Methods: Images (a 3 × 3 mm cube centered on the fovea) were acquired in 40 eyes of 22 normal individuals and 28 eyes of 18 patients with varying levels of DR using a swept-source OCT-A device (central wavelength 1050 nm; A-scan-rate of 100,000 scans per second). En face images of the retinal vasculature were generated from the superficial and deep retinal layers (SRL/DRL). Quantitative analysis of the vessel density (VD) and FAZ area was performed. Vessel density was assessed as the ratio of the retinal area occupied by vessels. Results: Among the DR subjects (mean age, 72 years; 61% male), 35.7% of the eyes had mild, 35.7% moderate, and 7.1% severe nonproliferative DR (NPDR), and 21.4% and proliferative DR (PDR). The mean FAZ area in patients with DR and in normal individuals was 0.518 and 0.339 mm², respectively, for the SRL (P = 0.003), and 0.615 and 0.358 mm², respectively, for the DRL (P < 0.001). The mean VD (ratio) at the SRL and DRL was statistically significantly lower in patients with DR (SRL, P < 0.001; DRL, P = 0.028). Conclusions: Swept-source OCT-A of the microcirculation in eyes of patients with DR can be used to quantitatively demonstrate alterations in the FAZ and VD in the SRL/DRL of the macula compared to normal eyes. Future longitudinal studies may use these metrics to evaluate changes over time or in response to treatment.

Optical coherence tomography angiography (OCTA) is a rapidly evolving technology that enables noninvasive visualization of the microvascular flow in the retina by comparing the signal in consecutive B-scans at the same location to reveal the motion of erythrocytes. Because of its high-axial resolution, OCTA enables visualization of fine retinal vasculature in multiple layers that is difficult to achieve with conventional dye-based angiography.^1,2 Optical coherence tomography angiography further provides an opportunity to generate quantitative metrics to describe the status of the retinal vasculature. Optical coherence tomography angiography–derived metrics described in previous reports include vessel density or perfusion density (PD),³ blood flow index,³ skeletonized density or vessel length density (VLD),⁴ and fractal dimension.⁵

Purpose: Increasing drusen volume was proposed to be a predictor of disease progression in age-related macular degeneration (AMD). In patients with late AMD in one eye, the fellow eyes without neovascularization are known to be at higher risk of developing exudative AMD. We evaluated the relationship between drusen volume in these fellow eyes and their progression to late AMD. Methods: A retrospective analysis included fellow eyes with drusen associated with nonexudative AMD. All eyes with neovascular AMD were treated with intravitreal ranibizumab, aflibercept, and/or bevacizumab and followed for 2 years. All eyes were scanned with the Cirrus HD-OCT using a 512 × 128 scan pattern. Optical coherence tomography (OCT) data at baseline, month 12, and month 24 were collected using the advanced RPE analysis tool to quantify drusen volume within 3- and 5-mm-diameter circles centered on the fovea. Optical coherence tomography scans were also evaluated for the development of geographic atrophy (GA) or macular neovascularization (MNV). Results: Eighty-nine patients who had neovascular AMD in only one eye were studied. Optical coherence tomography drusen volume in the absence of MNV could be measured in 61 participants (68.5%). After 12 months, 4 eyes (4.5%) developed MNV and 15 eyes (16.9%) developed GA. By 24 months of follow-up, an additional 5 eyes (7.1%) developed MNV and an additional 10 eyes (14.3%) developed GA. At month 24, the eyes that developed GA or MNV had baseline drusen volumes that were significantly larger than in eyes that did not develop late AMD. Patients with a drusen volume over 0.03 mm³ had a greater than 4-fold increased risk for developing late AMD compared with those with lower drusen volumes. Conclusions: Baseline drusen volume appears to be an important predictor for the development of late AMD within 2 years in eyes that have fellow eyes being actively treated for MNV. This suggests that OCT-derived drusen volume measurements may be a useful biomarker to identify eyes at the highest risk for progression to late AMD.