Toric ophthalmic lens
AssigneeKowa Company, Ltd.
InventorsKimiya Shimizu, Haruo Ishikawa
Life of this patent
Estimating the term…
Abstract
A tonic ophthalmic lens is described in which refractivity of the lens differs between a first direction on a plane perpendicular to an optical axis of the lens and a second direction which differs from the first direction on the plane. In addition, refractivity difference which is the difference between the refractivity in the first direction and the refractivity in the second direction varies depending on a position of the lens in a radial direction.
Claims9
A toric ophthalmic lens wherein refractivity of the lens differs between a first radial direction of the lens on a plane perpendicular to an optical axis of the lens and a second radial direction of the lens which differs from the first radial direction,
- wherein refractivity difference which is the difference between the refractivity at a first position that resides on a line extending in the first radial direction and the refractivity at a second position that resides on a line extending in the second radial direction and corresponds to the first position continuously varies in a stepless manner according to a variation of the first position and the second position from the center of the lens.
A toric ophthalmic lens wherein refractivity of the lens differs between a first radial direction of the lens on a plane perpendicular to an optical axis of the lens and a second radial direction of the lens which differs from the first radial direction, wherein the following formulas (1) to (6) are established,
- P
- 1
- =
- 1
- f
- 1
- (
- 1
- )
- P
- 1
- ′
- =
- 1
- f
- 1
- ′
- =
- 1
- f
- 1
- +
- SA
- 1
- (
- 2
- )
- P
- 2
- =
- 1
- f
- 2
- (
- 3
- )
- P
- 2
- ′
- =
- 1
- f
- 2
- ′
- =
- 1
- f
- 2
- +
- SA
- 2
- (
- 4
- )
- P
- C
- =
- P
- 1
- -
- P
- 2
- (
- 5
- )
- P
- C
- ′
- =
- P
- 1
- ′
- -
- P
- 2
- ′
- (
- 6
- )
- wherein P1 is first refractivity at a first position in a paraxial portion of the lens that resides on a first line extending in the first radial direction, P1′ is second refractivity at a second position in a peripheral portion of the lens that resides on the first line extending in the first radial direction, P2 is third refractivity at a third position corresponding to the first position in the paraxial portion of the lens that resides on a second line extending in the second radial direction, P2′ is fourth refractivity at a fourth position corresponding to the second position in the peripheral portion of the lens that resides on the second line extending in the second radial direction, f1 is a focal length in the first radial direction of the lens, SA1 is a distance of amounts of spherical aberration at the second position in the first radial direction of the lens, f2 is a focal length in the second radial direction of the lens, SA2 is a distance of amounts of spherical aberration at the fourth position in the second radial direction of the lens,
- PC and PC′ are determined based on a measurement of an eyeball in which the lens is mounted so as to cancel a difference between a refractivity in the paraxial portion of the eyeball and a refractivity in the peripheral portion of the eyeball, respectively, and
- PC and PC′ are configured to continuously vary in a stepless manner.
Dependencies are inferred from the claim text.