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A versatile Hartmann-Shack (HS) wavefront sensor (WFS) was designed and constructed. Its advantages include simultaneous pupil centre determination, off-axis capability, realtime data displays, and efficient lenslet sampling orientation. The instrument is compact and transportable, making it convenient for use in a clinical setting. Subject alignment is achieved by the use of a parallel channel that is recombined with the sensing channel to simultaneously image the external eye and the HS spots onto a single charge coupled device (CCD). The pupil centre is determined using this image of the eye, rather than the HS spots. Off-axis measurements are possible throughout an unobstructed 10 degree field of view. User-friendly software was developed to provide the clinician with data displays at 10 Hertz and above. The optical design includes a rotated lenslet array which increases the dynamic range in those meridians where astigmatism is most typically expected in the eye. Telecentric re-imaging of the HS spots increases the system’s robustness to CCD misalignment. Our experimental WFS was used in two experiments. The first experiment examined agreement between the experimental WFS and the ZyWave (a commercially available WFS) for monochromatic aberrations measured on 21 normal eyes. The second experiment investigated the variation of monochromatic aberrations over the central visual field. Measurements were performed on 60 normal eyes and the data was used to produce a statistical model of population distributions of Zernike coefficients. It is hoped this data will aid future designs for ocular multi-conjugate adaptive optics systems endeavouring to achieve wide-field high resolution retinal images.
Sheehan, M. (2008). Ocular aberrations wavefront sensor in clinical application. Masters dissertation. Technological University Dublin. doi:10.21427/D7RG7H