Truncated diffractive intraocular lenses
In one aspect, the present invention provides a method of designing a diffractive ophthalmic lens (e.g., an intraocular lens (IOL)) that includes providing an optic having an anterior refractive surface and a posterior refractive surface, wherein the optic provides a far-focus power (e.g., in a range of about 18 to about 26 Diopters (D)). A truncated diffractive structure can be disposed on at least one of the surfaces for generating a near-focus add power (e.g., in a range of about 3 D to about 4 D). And the diffractive structure can be adjusted so as to obtain a desired distribution of optical energy between the near and far foci for a range of pupil sizes.
1 . An ophthalmic lens, comprising
an optic having an anterior surface and a posterior surface,
a diffractive structure disposed on at least one of said surfaces,
said diffractive structure comprising a plurality of diffractive zones separated from one another by a plurality of steps having decreasing heights as a function of radial distance from an apex of said surface,
wherein said step heights are defined in accordance with the following relation:
h
=
b
*
λ
(
n
2
-
n
1
)
wherein
h represents the physical step height,
λ denotes the design wavelength,
n 1 denotes the refractive index of a medium surrounding the lens,
n 2 denotes the refractive index of the material forming the lens, and
b is defined in accordance with the following relation:
b
=
phas
0
(
1
+
r
rcontrol
)
rolloff
,
wherein
b represents the phase delay as a fraction of 2π,
phase 0 represents the overall (cumulative) optical phase delay across the diffractive steps,
r control represents the overall extend of the apodization region,
rolloff defines the steepness of the slope of the apodization profile.
2 . The ophthalmic lens of claim 1 , wherein
Phase 0 can be in a range of about 0.4 to about 0.7,
r control can be in a range of about 1 to about 2, and
rolloff can be in a range of about 5 to about 200.
3 . The ophthalmic lens of claim 1 , wherein at least one of said anterior or posterior surfaces includes an aspherical base profile.
4 . The ophthalmic lens of claim 3 , wherein said profile is characterized by a conic constant in a range of about −10 to about −1000.
5 . The ophthalmic lens of claim 3 , wherein said base profile is defined by the following relation:
z
=
cr
2
1
+
1
-
(
1
+
k
)
c
2
r
2
wherein,
z denotes the surface sag at a radial location r from the apex of the surface (the intersection of the optical axis with the surface),
c denotes the curvature of the surface at its apex,
r denotes the radial distance from the apex of the surface, and
k denotes the conic constant,
wherein,
c can be in range of about 0.001 mm −1 to about 0.1 mm −1 ,
r can range from about 0 to about 7 mm, and
k can be in a range of about −10 to about −1000.
6 . The ophthalmic lens of claim 1 , wherein at least one of said anterior or posterior surfaces exhibits a toric base profile.
7 . An ophthalmic lens, comprising
an optic comprising an anterior surface and a posterior surface,
a diffractive structure disposed on a central portion of one of said surfaces surrounded by a peripheral portion of the surface that is devoid of diffractive structures,
wherein one of said peripheral or central portions is characterized by a spherical base profile and the other portion is characterized by an aspherical base profile.
8 . The ophthalmic lens of claim 7 , wherein said ophthalmic lens comprises an IOL.
9 . An ophthalmic lens, comprising
an optic having an anterior surface and a posterior surface, and
a truncated diffractive structure disposed on a portion of one of said surfaces, said diffractive structure being characterized by a plurality of diffractive zones separated from one another by substantially uniform step heights,
wherein at least one of said surfaces exhibits a toric base profile.
10 . The ophthalmic lens of claim 9 , wherein said ophthalmic lens comprises an IOL.