Binocular Shack–Hartmann sensor for the human eye

During steady-state fixation the aberrations of the human eye display dynamic behaviour. It has been suggested that the fluctuations in focus are correlated between both eyes. However, nothing is known about the dynamic correlation between the aberrations other than focus. We have developed an open-view binocular Shack–Hartmann sensor which measures the ocular wavefront aberrations simultaneously in both eyes at 25 Hz. A single sensor and laser source are used to reduce system cost and complexity. Speckle is reduced using a rotating diffuser in a plane conjugate to the retinae. We measured the wavefront dynamics of two subjects and decomposed the data into Zernike aberration terms up to and including fifth radial order. Coherence function analysis was used to determine the correlation between aberrations in the frequency domain. The correlations were dependent upon subject, frequency and aberration type.