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Yifan Jian, John Werner, Kevin Wong, Edward Pugh, Marinko Sarunic, Robert Zawadzki; Imaging the mouse retina in vivo using Adaptive Optics - Fourier Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2013;54(15):396. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Non-invasive retinal imaging in small animal models of retinal diseases is an increasingly important tool for vision scientists. The mouse eye with dilated pupil has a numerical aperture (NA) nominally 2.5X that of the human eye, and just as in humans, the aberrations prevent the full NA to be used for diffraction-limited imaging. In this report, we describe the combination of a refraction cancelling fundus lens with adaptive optics (AO) for FDOCT imaging of the mouse eye in vivo.
We have constructed a prototype FDOCT system with a lens-based AO system (Fig.1) integrated into the sample arm. We used an objective lens to focus the light through a fundus contact lens (Volk, Inc) that canceled refraction at the cornea. The AO system (Iris AO, Inc) comprises a deformable mirror with 111 actuators (37 hexagonal segments and 5 um stroke (tip/tilt/piston)) and 37 lenslets, with Hartmann-Shack wavefront sensor working in a 1:1 optical mapping of DM segments and WFS lenslets. The same light source was used for wavefront sensing and FDOCT, providing visual feedback of the position of the focal depth in the retina in real time. This new system was used to measure and correct residual aberrations of the mouse eye and fundus contact lens, as well as to image microscopic morphology of the retina in vivo.
Measurements of the wavefront error from a typical mouse eye with fundus contact lens and the best focus (AO off) was on the order of 200nm RMS error. By activating the AO system, the measured wavefront was reduced to < 60nm RMS error. This corresponds to diffraction-limited imaging as defined by λ/14. Representative images of the mouse retina are presented in Fig. 2.
We have demonstrated retinal imaging in mice with AO-FDOCT, reducing the size of speckle in the images and increasing the resolution and contrast of features in the eye (blood vessels, nerve fibers, etc). By using a fundus lens to cancel refraction at the cornea, we demonstrated that high resolution retinal imaging can be performed in mice in vivo with an off-the-shelf AO system. Isoflurane gives highly stable and rapidly reversible anesthesia with none of the side effects associated with ketamine/xylazine.
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