Abstract
Purpose :
The impact of acute retinal ischemia has been explored in vivo with optical coherence tomography angiography (OCTA). However, because previous studies investigated only one to two time points after injury, the time course of OCTA changes after ischemia is unknown. The goal of this study was to explore the longitudinal relationship between retinal perfusion, retinal thickness and retinal ganglion cell (RGC) loss in a model of retinal ischemia in mice.
Methods :
24 adult female C57Bl/6 mice were divided evenly into groups receiving 15-, 30- or 45-minutes of retinal ischemia, induced by elevating intraocular pressure with a cannula in the anterior chamber connected to a pressure reservoir. A non-ischemic repeatability (NIR) group of 4 mice was used for comparison. Imaging sessions were performed at baseline and then at 1-, 3-, 5-, 7- and 10-days post-ischemic insult (PII). Perfusion density (PD) in the superficial, intermediate and deep capillary plexuses, and ganglion cell complex (GCC) thickness were calculated at all time points. Following the last imaging session, immunohistochemistry was performed to quantify RGC loss with RNA binding protein with multiple splicing.
Results :
No significant differences were found in PD between the NIR, 15- and 30-minute ischemia groups in any capillary plexus, at any timepoint. Due to significant structural damage in the 45-minute ischemia group, PD was alternatively calculated with a custom vascular volume encapsulating all three capillary plexuses. In the 45-minute ischemia group PD was significantly lower than the NIR group at all timepoints PII (Fig. 1). No significant differences were found in GCC thickness between the NIR, 15- and 30-minute ischemia groups at any time point (Fig. 2). When compared to the other three groups, the 45-minute ischemia group had significantly higher GCC thickness at 1-day and significantly lower GCC thickness at 5-, 7- and 10-days PII. There were no statistical differences in mean RGC density among the control, 15- and 30-minute ischemia groups (Fig. 2), however, the 45-minute group had a significantly lower value compared to the other groups.
Conclusions :
When compared to the NIR group, 45 minutes of ischemia appeared to cross a threshold for significant perfusion, structure and RGC loss within the retina. Shorter periods of ischemia appeared to cause minimal changes.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.