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S. A. Burns, Z. Zhong, X. Qi, A. E. Elsner; Multi-Wavelength Imaging and Image Quality for a Dual Deformable Adaptive Optics SLO. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3454.
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© ARVO (1962-2015); The Authors (2016-present)
A limitation for Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) imaging has been the small field size and need to refract subjects in the instrument. We have designed and constructed an AOSLO implementing programmable steering over 30 degrees, dual deformable mirrors to correct +4 to -9D ammetropia, and with variable wavelength imaging.
The newly constructed AOSLO was used to image the retina of more than 20 subjects, many with undilated pupils since imaging fields are relatively dim. A supercontinuum laser provided the imaging and beacon lights. Wavelengths for imaging were chosen using narrow-band filters (Semrock) to allow imaging at 800 nm (10 nm half width), 843 nm (12 nm half width), 832 (25 nm half width), and 840 nm (approximately 80 nm half width). A separate fiber was used to deliver the beacon light source at 740 nm. Dual deformable mirrors were used, one with high dynamic range, high stroke (Mirao 52d) and one with a smaller stroke, but high accuracy (Boston Micromachines).
Imaging in the new system met design specifications, including lateral resolution and the effects of wavelength. Images were obtained readily over the central 30 degrees of the retina. Subjects were successfully tested using the deformable mirrors from +1D to -8.5D without additional refractive correction. Imaging performance changed little with wavelength, although the wide bandwidth imaging beam produced slightly better images of cones near the fovea, predicted from decreased interference. Images of the smallest resolved cones occurred with a center-to-center spacing 0f 2.7 microns , very close to the diffraction limited prediction. This was confirmed by analyzing the full width of images of unusually bright cones, which was approximately 5 microns (representing the convolution of the cone size and psf). Narrower bandwidth shorter wavelengths produced slightly sharper images of processes near blood vessels, as expected from slight increases in resolution with shorter wavelengths. Vascular shadows changed little with wavelength. As little as 50uW of imaging light and 26 uW of beacon light produced high quality images.
AO systems can be built that allow most subjects with clear lenses to be imaged rapidly and reliably at any location within the arcades without requiring careful subject refixation. The abilty to now control bandwidth and centerwavelength allows testing specific models of light-tissue interactions at high resolution.
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