  The pyramid wavefront sensor (P-WFS) has replaced the Shack-Hartmann (SH-)
WFS as sensor of choice for high performance adaptive optics (AO) systems in
astronomy because of its flexibility in pupil sampling, its dynamic range, and
its improved sensitivity in closed-loop application. Usually, a P-WFS requires
modulation and high precision optics that lead to high complexity and costs of
the sensor. These factors limit the competitiveness of the P-WFS with respect
to other WFS devices for AO correction in visual science. Here, we present a
cost effective realization of AO correction with a non-modulated PWFS and apply
this technique to human retinal in vivo imaging using optical coherence
tomography (OCT). P-WFS based high quality AO imaging was, to the best of our
knowledge for the first time, successfully performed in 5 healthy subjects and
benchmarked against the performance of conventional SH-WFS based AO. Smallest
retinal cells such as central foveal cone photoreceptors are visualized and we
observed a better quality of the images recorded with the P-WFS. The robustness
and versatility of the sensor is demonstrated in the model eye under various
conditions and in vivo by high-resolution imaging of other structures in the
retina using standard and extended fields of view.
