Purpose
A feature of OCT angiography is its ability to provide quantitative estimate of retinal blood flow by calculating vessel density. This study examines macular blood flow using OCT angiography in eyes with angiographically active retinal vasculitis compared to normal eyes.
Methods
Adult patient with retinal vasculitis were imaged with fluorescein angiography (FA) and OCT angiography with 70 kHz OCT, using the split-spectrum amplitude decorrelation angiography algorithm (SSADA). A 3 x 3 mm angiogram centered at the fovea was obtained by projecting the flow signal internal to the RPE in the en face orientation. Parafoveal vessel density was defined as percentage of pixels with detectable flow signal in a 1mm-wide ring surrounding the fovea (Fig. 1A). The choriocapillaris vessel density was calculated as a percentage of pixels with detectable flow signal within 10 microns external to the RPE in the 3x3mm area.
Results
5 patients (7 eyes) with angiographically active retinal vasculitis were included in the study. Their diagnoses included lupus retinal vasculitis with choroiditis, Bechet’s disease, TINU with retinal vasculits, sarcoidosis, and idiopathic retinal vasculitis. 11 normal eyes were drawn from a prevously compiled database. The average vessel density in normal eyes, in a 1mm wide parafoveal ring (Figure 1A), was 87.1% (95% CI 83.9-90.2). In eyes with retinal vasculitis, the average parafoveal vessel density (see Figure 1B for example) was significantly lower, at 79.8% (95% CI 76.3-83.4, p=0.006). We also imaged choroidal blood flow in the patient with lupus vasculitis and choroiditis. Her choriocapillaris vessel densities were 83.3% and 83.6% in the right and left eyes, respectively, compared to 96.3% (95%CI 94.0%-98.5%) in normal eyes (n=7).
Conclusions
Patients with retinal vasculitis have significantly lower parafoveal vessel density compared to normal eyes, as measured by OCT angiography. Lower parafoveal vessel density was noted even in patients who had only peripheral vasculitis on FA. This technique shows promise as a possible biomarker for determining disease activity, and gauging treatment response in patients with retinal vasculitis.