Aspheric lenses
View Patent ↗The present invention provides monofocal ophthalmic lenses that exhibit extended depth of field while providing sufficient contrast for resolution of an image over a selected range of defocus distances. In some embodiments, a lens of the invention can include a refractive surface having controlled surface modulations relative to a base profile. The surface modulations are designed to extend a depth of field of the lens such that a single image can be resolved, albeit with somewhat less contrast, over a range of distances greater than the focal region of a conventional lens. The ophthalmic lenses of the invention can be employed in various vision correction applications, including, but not limited to, intraocular lenses, contact lenses, instrastromal implants and other refractive devices.
1. A monofocal ophthalmic lens having an extended depth of field, comprising
a lens optic providing a nominal diopter power and further characterized by at least one refractive surface having a base curvature, and
a pattern of surface deviations superimposed on said base curvature so as to modulate the topography of said refractive surface in a range of about −0.5 microns to about 0.5 microns so as to enhance a depth of field of said lens by at least about 40% relative to a lens having said lens optic and said refractive surface without said surface deviations.
2. The monofocal lens of claim 1 , wherein a through-focus modulation transfer function of said lens indicates an MTF contrast level of at least about 0.15 at spatial frequencies less than or equal to about one-third of a diffraction limited spatial frequency associated with said lens.
3. The monofocal lens of claim 1 , wherein said pattern of surface deviations is characterized by a continuously varying current.
4. The monofocal lens of claim 3 , wherein said pattern of surface deviations is characterized by a sinusoidal type curve.
5. The monofocal lens of claim 3 , wherein said base curvature is radially symmetric.
6. The monofocal lens of claim 5 , wherein said pattern of surface deviations is radially symmetric.
7. A monofocal ophthalmic lens for vision correction having an extended depth of field, comprising
a lens optic comprising a refractive surface having a base profile modulated by a pattern of surface deviations in accordance with the relation:
Z ( r )= A ( r )cos( B ( r ) r 2 )
wherein Z(r) denotes a surface deviation at a radial distance r from an optical axis of said lens, and A(r) and B(r) are functions of radial distance r selected so as to enhance a depth of field of said lens by at least 50% relative to a lens having said lens body and said refractive surface without said surface deviations.
8. The monofocal lens of claim 7 , wherein A is selected to have a maximum value in a range of about 0.05 microns to about 0.5 microns.
9. The monofocal lens of claim 8 , wherein A is selected to have a maximum value in a range of about 0.15 microns to about 0.45 microns.
10. The monofocal lens of claim 8 , wherein B is selected to have a minimum value in a range of about
2
π
5
to about 2π.
11. The monofocal lens of claim 7 , wherein A is selected to have a maximum value in a range of about
1
100
*
(
n
2
-
n
1
)
to about
1
10
*
(
n
2
-
n
1
)
microns, wherein n 2 denotes an index of refraction of said lens body and n 1 denotes an index of refraction of an environment in which the lens is disposed.
12. The monofocal lens of claim 8 , wherein A(r) and B(r) are defined as polynomials in accordance with the relations:
A ( r )= a 0 +a 1 r+a 2 r 2 + . . . +a n r n
B ( r )= b 0 +b 1 r+b 2 r 2 + . . . +b n r n
wherein n is selected to be less than about 20, and parameters a 0 -a n and b 0 -b n are selected so as to provide said enhanced depth of field.
13. The monofocal lens of claim 1 , wherein said lens body is formed of a biocompatible soft material.
14. The monofocal lens of claim 1 , wherein said lens body is formed of any of hydrogel, silicone or a soft acrylic material.
15. The monofocal lens of claim 1 , wherein said lens body is formed of a copolymer of acrylate and methacrylate.
16. The monofocal lens of claim 1 , wherein said lens provides nominal focal power in a range of about 20 to about 22 Diopters.
17. A method for generating an intraocular lens for vision correction having an extended depth of field, comprising
selecting a circularly symmetric base profile for at least a refractive surface of said lens,
defining a circularly symmetric continuously varying pattern of surface deviations from said base profile, and
applying said pattern of surface deviations to said base profile to define a continuously varying topography for said refractive surface,
wherein said pattern of surface deviations is defined so as to enhance a depth of field of said lens by at least about 50% relative to a lens having a refractive lens with said base profile without said surface deviations.
18. The method of claim 17 , wherein the step of defining the pattern of surface deviations from the base profile further comprises
selecting a plurality of locations on said base profile each at a selected radial distance from an optical axis of said lens,
for each of said locations, defining a position deviated from said location in a direction perpendicular to a radial direction and further defining a slope at said deviated position,
utilizing a spline fitting procedure to define a continuously varying surface extending through said deviated positions and having said defined slopes at each of said deviated positions,
determining an enhancement of a depth of field of said lens provided by employing said continuously varying surface as a profile of said refractive surface, and
adjusting iteratively one or more of said deviated positions and/or said slopes at said deviated positions such that the enhancement of the depth of field is at least about 50%, thereby determining an optimal pattern of surface deviations.