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Yang Lu, R Daniel Ferguson, Mircea Mujat, Gopi N Maguluri, James D Akula, Nicusor Iftimia; Short Wavelength Multi-aperture Imaging with the Multimodal Adaptive Optics Small-animal Imager (MAOSI). Invest. Ophthalmol. Vis. Sci. 2019;60(9):4590.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal vascular abnormalities are a feature of all blinding diseases of the retina, and are thus an area of central focus in translational vision research. The high numerical aperture of the mouse eye allows high-resolution imaging of retinal microvasculature. In a second-generation MAOSI, we evaluated whether murine retinal microvasculature imaging could be improved by incorporating blue wavelengths (445 nm) and split-detector AO-SLO imaging modalities for direct measurement of light absorption of retinal erythrocytes, supplemented by near infrared AO-OCT and red AO-SLO confocal reflectance imaging. We describe a pilot study MAOSI performance.
We adopted simultaneous, co-scanning AO-SLO/OCT rasters to assist image guidance, cross-modal registration and averaging. We carefully managed light levels to minimize possible light damage while benefiting from the high molar extinction coefficient of oxyhemoglobin and deoxyhemoglobin in the blue to enhance detection sensitivity. The incorporation of multi-aperture fiber bundles captured photons forward-scattered by vessels and enabled the split-detector AO-SLO imaging modalities. The blue and red channels were equipped with independent focus control to ensure both channels focuse precisely at the same depth. Moreover, the detection planes could be respectively shifted relative to the AO-OCT channel, which served as the beacon for the AO correction. To maintain body temperature while positioning the animal under isoflurane inhalation anesthesia, the mice (n=9 C57Bl/6) were held in a heated 6-degree-of-freedom stage. The imaging and anesthesia procedures follows an approved IACUC protocol.
Both blue and red wavelengths captured the retinal vasculature to the capillary level. In larger vessels, we observed significantly higher venular than arteriolar blue light absorption. Further, specular glints from tumbling erythrocytes were attenuated in the offset (blue) detectors, facilitating more accurate measurement of light transmittance from blood.
We present the first test of blue wavelength confocal and split-detector imaging on mouse retinal vasculature in our upgraded MAOSI platform. The short wavelength capability, combined with the AO-SLO/AO-OCT imaging modalities, may provide researchers with higher resolving power of the smallest retinal structures and also the ability to perform novel functional/metabolic imaging.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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