Patent ID: 7824033

Claim:
A method of characterizing cylinder in a person's eye, comprising: (a) determining an axis of said eye; (b) providing a target image having at least one feature that may be oriented either substantially parallel or substantially perpendicular to said axis; (c) selecting a first refractive correction (D 1 ) when the at least one feature is substantially parallel to said axis, wherein selecting a refractive correction comprises: (i) repetitively measuring wavefronts emanating from the person's eye for different amounts of refractive correction, said act of repetitively measuring wavefronts comprising performing multiple wavefront measurements using a wavefront sensor; (ii) producing a plurality of data sets for the plurality of refractive corrections, respectively, said data sets comprising data points indicative of the quality of vision of the person; (iii) calculating the variation in said plurality of data points to provide an objective assessment of the refractive correction for each of said data sets; (iv) comparing said variations and selecting an amount of refractive correction based on said comparison; (d) selecting a second refractive correction (D 2 ) when the at least one feature is substantially perpendicular to said axis; and (e) determining said cylinder of said patient's eye based at least in part on the values of D 1 and D 2 .