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T. Yamaguchi, N. Nakazawa, Y. Takahashi, T. Mihashi, N. Maeda, T. Fujikado; Adaptive Optics Fundus Camera using Liquid Crystal Phase Modulator. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2793.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Adaptive optics that compensate human eye aberrations may be used to try to achieve diffraction limited imaging of human eye (Liang, Williams, and Miller (1997) J. Opt. Soc. Am; Roorda and Williams (1999) Nature). An adaptive optics fundus camera that uses a liquid crystal phase modulator was built and feasibility of aberration compensation by the phase modulator was investigated. Fundus images obtained with the adaptive optics were compared to those obtained without adaptive optics. Methods: The Adaptive optics fundus camera consisted of conventional type imaging optics (not confocal optics), a Shack–Hartmann wavefront sensor, and a liquid crystal phase modulator (PAL, Hamamatsu Photonics) for compensating aberrations. The spatial resolution of the modulator was 640×480, which is much higher than that of most mechanical deformable mirrors. The wavelength for imaging was 640 nm and that for wavefront sensing was 690 nm. The aberration of the eye was measured using the S–H sensor in real time. We confirmed the capabilities of the adaptive optics using a model eye and a human eye dilated for larger numerical aperture and higher resolution. Results: A drawback of the modulator was that it modulates in only one plane of polarization. One compensation cycle took 250 ms in which the liquid crystal modulator took 100 ms to refresh and the wavefront sensor took 100 ms to measure wavefront aberrations. The modulator reduced the aberrations of a model eye with 0.25 diopter astigmatism from 0.66 microns to 0.13 microns (for an 8 mm pupil), and an artificial 5 micron pattern on the bottom of the model eye was clearly observed. A human eye was measured and aberration of the eye was reduced by adaptive optics from 0.31 micron to 0.09 micron for 5 mm pupil. When adaptive optics were active, small structures in the retina were seen which were not observable without compensation. Conclusions: The aberration compensation by the liquid crystal light modulator gave better resolution in fundus camera for imaging of small structures such as cones.
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