The spatially resolved refractometer

PURPOSE: To investigate factors controlling the aberrations of the eye, including accommodation, wavelength, and the apodization of the optics of the eye by cone directional selectivity. METHODS: We constructed a new implementation of the Spatially Resolved Refractometer (SRR). This is an instrument, based on the Scheiner principle, that allows the rapid psychophysical measurement of the complete wavefront aberrations of the eye. We have investigated both the reproducibility of the measurements, and the effect of static accommodation and wavelength on the wavefront aberrations of the eye. In addition we combined the wave front aberrations with cone photoreceptor directionality to compute the modulation transfer function of the eye, at the retinal level. RESULTS: The SRR measurements were rapid (4 minutes per measurements, 12 minutes per patient) and reproducible. There are significant changes in wavefront quality with accommodation, with optimal image quality near the resting point of accommodation. Image quality for polychromatic (white) light is strongly affected by both longitudinal and transverse chromatic aberration. Finally, we find that incorporating the effects of cone directionality into the calculation of image quality can increase image quality by up to 50%. CONCLUSION: Calculation of a simple "optimal surgical shape" for wave-front guided refractive surgery will depend on improved understanding of the interplay between the biological and physical properties of the eye.