Purpose:
It has been argued that the radial peripapillary vasculature, which supplies the thickest portions of the nerve fiber layer, may be importantly involved in the etiology of glaucoma. However, this vasculature is challenging to image, making this hypothesis difficult to evaluate. Here we report the ability to image radial peripapillary vessels using intravenous fluorescein, together with a fluorescence adaptive optics scanning laser ophthalmoscope (AOSLO).
Methods:
We injected sodium fluorescein intravenously in sedated macaque monkeys and then imaged the retina with a fluorescence adaptive optics scanning laser ophthalmoscope. An argon/krypton laser provided 488 nm excitation light for fluorescence imaging. Reflectance images, obtained simultaneously with light from an 830 nm laser diode, permitted precise registration of individual frames of the fluorescence imaging.
Results:
Superficial focus revealed a vasculature with thin walls, little variation in caliber and parallel linked structure parallel to the nerve fibers (Figure 1B) typical of the radial peripapillary vasculature. When the focus was advanced 0.43D, typical reticular retinal capillary pattern was seen (Figure 1A).
Conclusions:
The radial peripapillary vasculature may be imaged in the living macaque by utilizing a through-focus technique in the retina following injection of sodium fluorescein. The peripapillary capillary network is visible with superficial retinal focus, and the retinal capillary network when the focus is moved toward outer retinal strata.Figure 1: Radial peripapillary vasculature imaged with adaptive optics. A. Mid-retinal focus on the retinal vasculature, B. Superficial retinal focus corresponding to radial peripapillary vasculature.
Keywords: retina • nerve fiber layer • blood supply