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S.R. Chamot, M. Sheehan, S. Esposito, J.C. Dainty; In vivo Aberrometry With a Pyramid Wavefront Sensor . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1182.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The Hartmann–Shack approach commonly used for sensing ocular aberrations and driving adaptive optics systems lacks dynamic range and sampling adjustability. Both clinical aberrometry or adaptive systems for imaging or studying vision could benefit of an enhanced sensing flexibility, therefore we studied the ophthalmic potentialities of the pyramid wavefront sensing principle. Methods: We implemented a pyramid wavefront sensor in an adaptive optics setup and used it in open loop to obtain wavefront measurements over a 6 mm pupil in 10 volunteers. The corresponding Zernike coefficients up to the 5th order were computed and compared with the values obtained with a commercial Hartmann–Shack based aberrometer (ZywaveTM). The linear defocus range of the system was measured with a set of trial lenses. Results: In the present configuration, the pyramid wavefront sensor covers a linear defocus range between –2.5 and +3 dioptres, however this range is extendable by increasing the amplitude of the beam modulation on the pyramid vertex. Depending on the pupil sampling (200 – 3300 lenslet equivalents) and with a probing laser power of 5 µW (635 nm), the instrument records wavefront gradients at 50 – 10 Hz, respectively. The 2nd order Zernike coefficients measured in 10 eyes with a pyramid and a Hartmann–Shack wavefront sensor were significantly correlated (N = 30, R = 0.572, p < 0.001). For each subject, the wavefront data obtained with different pupil sampling matched quite closely. Conclusions: The pyramid wavefront sensor appears suitable for measuring ocular aberrations. Its adjustable pupil sampling and dynamic range might allow either high–resolution ocular aberrometry or fast closed–loop adaptive optics control with the same wavefront sensor.
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