US-12616566-B2 - Adaptive multifocal diffractive ocular lens

US12616566B2US 12616566 B2US12616566 B2US 12616566B2US-12616566-B2

Abstract

An ophthalmic multifocal lens providing far, intermediate, and near vision having a light transmissive body with an optical axis and a refractive baseline extending over part of the lens body; further having a first portion coinciding with a central area of the lens body and a multifocal second portion extending concentrically radially; the second portion further comprising a symmetric multifocal diffractive grating superpositioned onto the baseline, covering a portion of the lens, its shape and resulting light intensity distribution changing with distance to optical axis, the first portion being substantially concave, connected to the ridge of the grating that is closest to the optical axis and provides a dominant optical power between intended far and intermediate powers; configured to have an energy ratio intended for far vision to energy intended for near vision being lower for predetermined aperture(s).

Inventors

Sven Thage Sigvard Holmström
Amin Tabatabaei Mohseni
Efe Can

Assignees

VSY BIYOTEKNOLOJI VE ILAC SANAYI A.S.

Dates

Publication Date: 20260505
Application Date: 20210219

Claims (14)

1 . An ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision, comprising a contact lens or an intraocular lens, said lens having a light transmissive lens body with an optical axis and a refractive baseline that extends over at least a part of the lens body, said lens further having a first portion that coincides with a central area of said light transmissive lens body, extending concentrically in a radial direction, and a multifocal second portion, extending concentrically in a radial direction, wherein said second portion of the ophthalmic multifocal lens further comprises a symmetric multifocal diffractive grating super positioned onto said refractive baseline, covering a portion of the lens, its shape and resulting light intensity distribution thereof changing with respect to its distance to the optical axis, said symmetric multifocal grating at least comprising one diffractive order contributing to far vision and one diffractive order contributing to near vision, a 0th order of said symmetric multifocal diffractive grating super positioned onto said refractive baseline substantially coincides with the power of the refractive baseline as well as an intended intermediate power of the lens, said first portion of said ophthalmic lens is configured so that super positioned onto said refractive baseline around the optical axis is a substantially concave shape, connected to the ridge of said symmetric multifocal diffractive grating that is closest to the optical axis, said refractive baseline provides a focal point substantially coinciding with the intermediate power, and; said first portion of said ophthalmic lens is configured to provide a dominant optical power that is in between the intended powers of far vision and intermediate vision, said ophthalmic multifocal lens is further configured such that; for an aperture of 5 millimeters, energy intended for near vision is weaker than energy intended for both intermediate and far vision respectively; for an aperture of 3 millimeters, intermediate energy is weaker than both the near and far energies respectively; and a ratio of energy intended for far vision to energy intended for near vision that is lower for an aperture of 3 mm compared to same ratio for apertures of 2 mm and 4.5 mm.
2 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein said ophthalmic multifocal lens is configured such that, for a 3-mm aperture, modulation transfer function ratio of far vision to near vision is lower than that for 2- and 4.5-mm apertures, measured at 50 lines per millimeter.
3 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein said symmetric multifocal diffraction grating further comprises a wave-type diffraction pattern, comprising alternating crest and trough amplitude values, whereby said first portion is concave from a point coinciding with the optical axis of the lens and up to a point that is configured to be of greater proximity to a crest amplitude value than that of a trough amplitude as measured along a direction normal to the optical axis.
4 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein the power difference of intermediate and far vision is configured to be between 1.5 D and 2.2 D, whereas the power difference of far and near vision is configured to be between 3 D and 4.4 D.
5 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein said first portion comprises a shape arranged for monofocality.
6 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein said symmetric multifocal diffraction grating provides a number of focal points that is selected from a group including, but not limited to, three, five, seven, and nine focal points.
7 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein at least one of said first portion, said second portion, or both said portions are combined with a sawtooth diffractive grating that is substantially monofocal for a design wavelength.
8 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein for apertures larger than 3.5 mm the lens comprises at least one optically active feature from a group including, but not limited to, an asymmetric diffractive grating, a shape providing refractive power other than that of said refractive baseline, and a symmetric diffractive grating with an odd number of focal points that is different from that of said symmetric multifocal diffractive grating.
9 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein said symmetric multifocal diffraction grating comprises within the 4.5 mm aperture at least two periods of said symmetric multifocal grating having the relation that, for the corresponding linear grating unit cells, the diffraction efficiency for an order responsible for near vision is at least ten percent higher for the period of the two periods that is located closest to the optical axis compared to the period located further from the optical axis.
10 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein a highest point, relative to said refractive baseline, of the crest closest to the optical axis of said multifocal grating is placed at a normal distance from the optical axis within the range of 0.47 mm to 0.75 mm.
11 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein a point of said first portion coinciding with the optical axis of said multifocal lens is configured to be lower compared to said refractive baseline than any other trough within the central 3 mm of said multifocal lens.
12 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein a maximum peak-to-peak height of said symmetric multifocal diffraction grating is, for a design wavelength, less than 50 percent of full phase modulation, calculated such that the trough of said first portion is omitted.
13 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 1 , wherein said lens when measured with a concentric 1-mm aperture has a dominating power that is between the intended far and intermediate powers.
14 . The ophthalmic multifocal lens, arranged to provide far, intermediate, and near vision as set forth in claim 13 , wherein said lens when measured with a concentric 1-mm aperture has a dominating power that is stronger than the intended power for far vision by at least 0.2 D, but not more than 1.2 D.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is the U.S. National Stage application of PCT application no. PCT/TR2021/050154, filed on Feb. 19, 2021, titled AN ADAPTIVE MULTIFOCAL DIFFRACTIVE OCULAR LENS, designating the United States, the contents of which are incorporated herein by reference in their entirety. TECHNICAL FIELD OF THE PRESENT INVENTION The present disclosure generally relates to ophthalmic lenses and, more specifically, to ophthalmic contact and intra-ocular multifocal lenses, the multifocality being provided by a diffractive structure that is arranged so as to best serve human vision over different pupil sizes. BACKGROUND OF THE PRESENT INVENTION Diffractive lenses for ophthalmological applications are constructed as hybrid lenses with a diffractive pattern added onto a refractive body. Often one side of the lens is purely refractive, while the other side has a diffractive grating superpositioned over a refractive base line. The refractive baseline can be spherical, or alternatively have an aspherical shape of sorts. A high order monofocal diffractive pattern can also function as a purely refractive shape. The diffractive part can in general be applied to any of the two sides of the lens, since when a diffractive pattern is to be combined with a refractive surface with some special feature it generally does not matter if they are added to the same side or if one is added to a first side and the other to a second side of the lens. Concurrently, two diffractive patterns may be combined either by super positioning on one side, or by adding them on separate sides in an overlapping fashion. The optical power of the lens for a specific diffraction order can be calculated by addition of the refractive base power and the optical power of that diffraction order. In the anatomy of the eye, light passes through an opening within the iris, called pupil, before reaching the lens and being focused onto the retina. The size of the pupil is governed by the muscles of the iris, so that it rapidly constricts the pupil when exposed to bright light and expands (dilates) the pupil in dim light. The pupillary aperture also narrows when focusing on close objects and dilates for more distant viewing. At its maximum contraction, the adult pupil may be less than 1 mm in diameter, and it may increase up to 10 times to its maximum diameter. The size of the human pupil may also vary as a result of age, disease, trauma, or other abnormalities within the visual system, including dysfunction of the pathways controlling pupillary movement. Based on the pupillary response in combination with the specific response of cones and rods in the eye's retina, three main modes of eye function under different illuminance levels (cd/m2) are observed: photopic (bright light), scotopic (low light conditions), and mesopic (intermediary). The brightness level of the observed object, the background and surroundings determine the activity of rods and cones by retinal illuminance level (light intensity). Additionally, the visual system is more sensitive to light coming in through the center of the eye pupil than to light entering from the periphery of the pupil. This is called the Stiles-Crawford Effect of the first kind (SCE-I), also known as the “directional sensitivity of the retina”, describes the angular dependence of retinal sensitivity. Axial light rays that enter the pupil near its center, which are parallel to retinal receptors, are more effective than off-axis light oblique rays, which enter the pupil near its margins. Therefore, light passing through the periphery of the pupil is less efficient at stimulating vision than light passing near the center of the pupil (i.e., axial light forms sharper images than off-axis light) and hence increases the depth of focus (referring to: W. Fink and D. Micol, “computer-based simulation of visual perception under various eye defects using Zernike polynomials,” J. Biomed. Opt., vol. 11, no. 5, p. 054011, 2006.). The SCE can significantly improve defocused image quality and defocused vision, particularly for tasks that require veridical phase perception (referring to: X. Zhang, M. Ye, A. Bradley, and L. Thibos, “Apodization by the Stiles-Crawford effect moderates the visual impact of retinal image defocus,” J. Opt. Soc. Am. A, vol. 16, no. 4, p. 812, 1999). Note that a diffraction grating that functions as a lens has a pitch that in absolute terms varies with the radius. The pitch depends on the refractive index, the design wavelength, and the optical power of the first diffraction order. The pitch is determined so that the optical path difference (OPD) through the lens to the focal point of the first diffraction order has a difference of exactly one wavelength per period. To show the periodicity of a diffraction grating one will often plot the diffractive lens profile versus the square of the radius. When plotted like this the periods (grating pitch) are equidistant, more exactly t