Using the Fourier analysis the wave-front at the exit pupil of a model eye is determined. This model eye is set up in an optical system which contains a Hartmann-Shack microlens array for measuring the optical quality of the eye. The aberrations of the model eye can be simulated by shaping the front surface of a contact lens whereupon we simulate the cornea. The lens eye is simulated by an achromat lens and the retina is simulated by a flat mirror.