Purpose:
To visualize in 3D and quantify in-vivo the early acute effect of sodium iodate-induced outer retina degeneration in rat retina using ultrahigh resolution optical coherence tomography (UHR-OCT) system.
Methods:
A research-grade, high speed, 1060nm UHR-OCT system with 3um axial resolution in biological tissue, was used to observe the early acute effect of sodium iodate in a rat model of outer retina degeneration. The outer retinal damage was induced by intravenous injection of 40 mg/Kg sodium iodate in 8 adult, female Long Evans rats. Volumetric UHR-OCT tomograms were acquired in a longitudinal study at baseline and every 2hours for up to 12 hours post drug injection. Four of the rats received 1mL subcutaneous PBS injections at 1hour and 3 hours post drug administration to provide additional body fluid.
Results:
The3D OCT tomograms show the appearance of a low reflective layer below the photoreceptor layer (PRL) within the first 6 hours post drug injection (fig.1A, green bracket). We hypothesize that this effect could be caused by swelling of the cells and/or fluid accumulation due to breakdown of the blood-retina barrier. Significantly stronger swelling effect (fig.1B, green bracket) was observed in the rats that were injected with PBS within the first 6 hours post injection of sodium iodate. Fig.1 shows representative images from rat retinas 6 hours post drug injection with (Fig.1.A) and without (Fig.1.B) PBS injection. The average thickness of the retina detached layer is about 15 µm in regular rats and 32 µm in the rats injected with PBS.
Conclusions:
We have used a state-of-the-art, high speed, UHR-OCT system to investigate and quantify the early acute effect of sodium iodate-induced retina degeneration in rat retina. Our results suggest that availability of more body fluid leads to more severe PRL detachment which is most likely linked to the breakdown of the blood-retina barrier and influx of fluid into the retinal space. Results from this study could potentially help better understanding of the mechanism of outer retina degeneration induced by sodium iodate and lead to refinement of existing models as well as development of new models for retinal disease.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • drug toxicity/drug effects