Progressive addition lenses with an additional zone
View Patent ↗The invention provides multifocal lenses containing at least four zones of refractive power. The zones are positioned such that the wearer is able to use the inferior-most portion of the lens to clearly view objects at distances more than about 45 cm from the eye.
1. A multifocal lens, comprising: a.) a distance vision power zone; b.) a near vision power zone comprising an add power; c.) an intermediate vision power zone between the distance and near vision power zones; and d.) a fourth zone located inferior to the near vision power zone, wherein the fourth zone has a constant power that is within about 20 to about 80% of the add power.
2. The lens of claim 1 , wherein the lens is a progressive addition lens.
3. The lens of claim 1 , wherein the refractive power of the fourth zone is about 25 to about 75% of the add power.
4. The lens of claim 1 , wherein the fourth zone is blended continuously with the near zone.
5. The lens of claim 1 , wherein a width of the fourth zone is about 5 to about 25 mm.
6. The lens of claim 5 , wherein a length of the fourth zone is about 10 to about 20 mm.
7. The zones of claim 1 , wherein each of the distance, intermediate, near and fourth zone are located on one surface of the lens.
8. The lens of claim 7 , wherein the zones are located on the front surface of the lens.
9. The lens of claim 8 , further comprising a back surface comprising one or more of a second distance vision power zone, a second near vision power zone, a second intermediate power zone, and a second fourth zone.
10. The lens of claim 9 , wherein the front and the back surfaces are misaligned.
11. The lens of claim 1 , further comprising a cylinder power.
12. The lens of claim 7 , further comprising a cylinder power.
13. The lens of claim 8 , further comprising a cylinder power.
14. The lens of claim 9 , further comprising a cylinder power.
15. The lens of claim 10 , further comprising a cylinder power.
16. A method for designing a lens, comprising the step of providing a lens comprising: a.) a distance vision power zone; b.) a near vision power zone comprising an add power; c.) an intermediate vision power zone between the distance and near vision power zones; and d.) a fourth zone located inferior to the near vision power zone, wherein the fourth zone has a constant power that is within about 20 to about 80% of the add power.
17. The method of claim 16 , wherein the fourth zone is a surface Z′ S (x, y) that is produced according to the equation:
Z′ S ( x, y )= Z S ( x, y )+ T*y+O
wherein Z S (x, y) is the fourth zone surface;
T is a tilt in an angle of the fourth zone surface in a direction y; and
offset by an amount O is an amount of offset in a direction z.
18. The method of claim 16 , further comprising combining the surface Z′ S (x, y) with a progressive surface Z P (x, y) to produce a surface Z(x, y) according to the equation:
Z ( x, y ) =F ( x, y ) *Z P ( x, y )+{1 −F ( x, y )}* Z′ S ( x, y )
wherein 0≦F(x, y)≦1; and
F(x, y) is a blending function.
19. The method of claim 18 , further comprising combining surface Z(x, y) with a complementary spherical surface.
20. The method of claim 18 , further comprising combining surface Z(x, y) with a complementary toric surface.