Multifocal refractive surgery optimized to pupil dimensions and visual acuity requirements

A method as in claim 1 of performing multifocal refractive surgery on the cornea of an eye, said method adjusting the zone dimensions to ensure that the acuity requirements are met as the pupil dimension declines with age, said method consisting of:

• (i) measuring the pupil dimensions in bright and dim light with near and distant focusing,
• (ii) reducing the pupil dimension by about 0.3 mm per decade of additional age desired for correction,
• (iii) recalculating the modulation transfer function, maximum frequency, and expected visual acuity as functions of the zone dimensions, arrangement and decentration, as in claim 1 or claim 19, based on the reduced pupil dimensions,
• (iv) determining the patient's near and distant visual acuity requirements, and
• (v) selecting the zone sizes, tolerances, decentration and arrangement, which meet the acuity requirements.

A method for performing multifocal refractive surgery on the cornea of an eye, said method correcting presbyopia, myopia, hyperopia, and regular and irregular astigmatism, said method creating a plurality of optical zones, at least one of said zones being corrected predominantly for near vision and at least one of said zones being corrected predominantly for distant vision, said method optimizing the decentration of said optical zones, said method comprising:

• (i) measuring the pupil diameters of patient's eyes in bright and dim light with near and distant focusing;
• (ii) alternatively, using the range of pupil measurements of the entire population, in bright and dim light, with near and distant focusing, said range being known in the literature;
• (iii) determining the patient's near and distant visual acuity requirements;
• (iv) measuring the refractive error of the patient's eyes;
• (v) preferably, measuring the optical aberrations of the patient's eyes;
• (vi) alternatively, assuming that the patient's optical aberrations are insignificant;
• (vii) preferably, measuring the patient's retinal contrast threshold as a function of the spatial frequency;
• (viii) alternatively, using the average human retinal contrast threshold as a function of the spatial frequency;
• (ix) selecting the overall dimension of the outermost corrected optical zone to exceed the pupil dimension in dim lighting with distant focusing;
• (x) selecting for investigation a candidate optical zone geometry, such as circular, annular, sectoral, ovoid and the like;
• (xi) selecting for investigation a candidate arrangement of the optical zones, such as correcting the central zone for distance, and other zones for near and intermediate focusing;
• (xii) selecting for investigation a candidate nominal optical power for each zone, to predominantly correct near, distant or intermediate visual acuity;
• (xiii) selecting for investigation a candidate optical power profile as a function of the location, such as bifocal, trifocal, linear or nonlinear aspheric multifocal and the like;
• (xiv) selecting for investigation a dimension for each of the optical zones;
• (xv) using the pupil measurements, focusing, zone dimensions, optical power profile, and aberrations, together with a series of optical zone decentrations, to create a series of mathematical models of the wavefront transmitted through the eye/multifocal optic system;
• (xvi) calculating the modulation transfer function for each said mathematical model of the wavefront;
• (xvii) calculating the maximum resolvable spatial frequency for each said modulation transfer function;
• (xviii) calculating the expected visual acuity for each said modulation transfer function;
• (xix) creating tables or graphs of the expected near and distant visual acuity as functions of the zone decentrations;
• (xx) comparing the patient's required near and distant visual acuity to the expected visual acuity as a function of the zone decentrations;
• (xxi) selecting the zone decentrations which provide expected visual acuity greater than or equal to the visual acuity requirements;
• (xxii) thereby determining the minimum and maximum zone decentrations;
• (xxiii) selecting an optimum zone decentration from the ranges defined by said minimum and maximum zone decentrations;
• (xxiv) creating an algorithm or table defining the required postoperative profile of the surface of the cornea;
• and
• (xxv) thereby programming a computer-controlled laser, thermal, electrical, mechanical, or other device, to reshape the cornea or a corneal implant, to produce said multifocal corneal surface profile.