Multifocal lenses for pre-presbyopic individuals
View Patent ↗The invention provides lenses suitable for use by pre-presbyopic individuals. The lenses of the invention have one or more non-conic, aspheric surfaces having substantially no noticeable unwanted astigmatism.
1. A method for designing a lens, comprising the steps of:
a.) designing a first surface that is a progressive addition surface P(x,y) using a base spherical surface P s (x,y);
b.) expressing the first surface P(x,y) as a plurality of sag values P o (x,y);
c.) altering locally one or more of the plurality of sag values P o (x,y) to provide a second surface N(x,y);
d.) adding the second surface N(x,y) to the base spherical surface P s (x,y) to obtain a non-conic aspheric surface comprising an add power and having a maximum unwanted astigmatism between about 50% and 60% of the non-conic surface's add power.
2. The method of claim 1 , wherein the lens is a spectacle lens.
3. The method of claim 2 , further comprising e.) smoothing the non-conic, aspheric surface.
4. The method of claim 2 , wherein step c.) is carried out using the equation:
N ( x, y )= P o ( x, y )+ A ( x, y ). W ( x, y )
wherein A is an altering function; and
W is a weighting function.
5. The method of claim 4 , wherein the weighting function is:
W
(
x
,
y
,
X
0
,
Y
0
,
σ
x
,
σ
y
,
ρ
)
=
Exp
(
-
[
(
x
-
X
0
σ
x
)
2
-
2
·
ρ
·
(
x
-
X
0
σ
x
)
·
(
y
-
Y
0
σ
y
)
+
(
y
-
Y
0
σ
y
)
2
]
/
(
2
·
(
1
-
ρ
2
)
)
)
wherein, X 0 and Y 0 are coordinates where a local alteration is maximal;
σ x and σ y are standard deviations of the x and y values; and
ρ is a correlation coefficient between x and y values.
6. The method of claim 4 , wherein the altering function is one or more of
A
Toric
(
x
,
y
,
r
1
,
r
2
,
θ
)
=
[
r
2
2
-
Y
0
2
+
r
1
-
r
2
]
2
-
X
0
2
+
r
1
wherein X o =x.Cos θ−y.Sin θ;
Y o =y.Cos θ−x.Sin θ;
r 1 is a large radius of curvature;
r 2 is a small radius of curvature; and
θ is a orientation of the large axis;
or
A
Atoric
(
x
,
y
,
r
1
,
r
2
,
θ
)
=
[
r
2
2
-
Y
0
2
+
r
1
-
r
2
]
2
-
X
0
2
+
r
1
+
A
1
·
S
4
+
A
2
·
S
6
+
A
3
·
S
8
+
A
4
·
S
10
wherein X o =x.Cos θ−y.Sin θ;
Y o =y.Cos θ−x.Sin θ;
r 1 is a large radius of curvature;
r 2 is a small radius of curvature;
θ is a orientation of the large axis;
A i is an aspheric term; and
S 2 =x 2 +y 2 ;
or
A
Aspheric
(
x
,
y
)
=
c
·
S
2
1
+
1
-
(
K
+
1
)
·
c
2
·
S
2
+
A
1
·
S
4
+
A
2
·
S
6
+
A
3
·
S
8
+
A
4
·
S
10
wherein c is the inverse radius of curvature;
S 2 =x 2 +y 2 ;
K is a conic constant; and
A i is an aspheric term.
7. A spectacle lens, comprising a non-conic, aspheric surface provided according to the method of claim 3 .
8. A spectacle lens, comprising a non-conic, aspheric surface provided according to the method of claim 4 .
9. A spectacle lens, comprising a non-conic, aspheric surface provided according to the method of claim 5 .
10. A spectacle lens, comprising a non-conic, aspheric surface provided according to the method of claim 6 .
11. The lens of claim 7 , wherein the non-conic, aspheric surface is a convex surface.
12. The lens of claim 8 , wherein the non-conic, aspheric surface is a convex surface.
13. The lens of claim 9 , wherein the non-conic, aspheric surface is a convex surface.
14. The lens of claim 10 , wherein the non-conic, aspheric surface is a convex surface.
15. The lens of claim 11 , further comprising a concave surface comprising correction for one or more of a lens wearer's astigmatism or prism.
16. The lens of claim 15 , wherein the convex surface further comprises a channel length of about 10 to about 22 mm.
17. The lens of claim 12 , further comprising a concave surface comprising correction for one or more of a lens wearer's astigmatism or prism.
18. The lens of claim 17 , wherein the convex surface further comprises a channel length of about 10 to about 22 mm.
19. The lens of claim 13 , further comprising a concave surface comprising correction for one or more of a lens wearer's astigmatism or prism.
20. The lens of claim 19 , wherein the convex surface further comprises a channel length of about 10 to about 22 mm.
21. The lens of claim 14 , further comprising a concave surface comprising correction for one or more of a lens wearer's astigmatism or prism.
22. The lens of claim 21 , wherein the convex surface further comprises a channel length of about 10 to about 22 mm.