Abstract
Purpose :
Optical coherence tomography angiography (OCTA) is a noninvasive angiographic method that compares the decorrelation signal over time to identify areas of changing signal. Erythrocyte Mediated Angiography (EMA) uses autologous ICG-labelled cells to permit the visualization and absolute quantification of retinal capillary flowrates. We aimed to compare and validate EMA with OCTA and then to compare the OCTA decorrelation and flow values at low and high pressures in a non-human primate model.
Methods :
Sequential OCTA and EMA was acquired in two sessions of two non-human primate (NHP) eyes at high and low intraocular pressures (Figure 1). OCTA was acquired using Heidelberg Spectralis (Heidelberg Engineering, Heidelberg, Germany), and EMA was acquired using previously described methods (Tracy 2019). OCTA decorrelation within capillaries of the superficial vascular plexus (SVP) was measured using manual segmentation. We then compared the values of OCTA decorrelation with EMA in the same vessels. We further compared OCTA decorrelation values at high and low IOPs.
Results :
In 15 SVP capillaries at low IOP and 11 at high IOP, EMA velocity was 0.61 +- 0.07 mm/s and 0.54 +- 0.21 mm/s respectively and OCTA decorrelation was 0.61 +- 0.06 and 0.56 +- 0.11 respectively (Figure 2). OCTA decorrelation values correlated with absolute EMA velocity (r = 0.50, p <0.05). In ten perifoveal SVP capillaries at high and low IOP, the mean OCTA decorrelation at a low IOP (Mean IOP = 14.5 mm Hg, OCTA decorrelation = 0.69 +- 0.11) was significantly higher than at high IOP (Mean IOP = 27.75 mmHg, OCTA decorrelation =0.49 +- 0.08, p <0.05).
Conclusions :
In our analysis, a large and statistically significant difference was observed between OCTA decorrelation at low and high IOP, and was correlated with changes in absolute erythrocyte velocity as measured with EMA. This potentially validates the decorrelation values of OCTA.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.