Ocular lens
To provide an ocular lens capable of securing a stable image in a distance portion and a near portion, and suppressing a generation of blurring or ghosting of the image. A progressive multifocal far and near contact lens is provided, having a distance portion for aiding a far vision, a near portion for aiding a near vision, and an intermediate portion in which power is progressively changed between the distance portion and the near portion, and a power distribution of a lens optical region along a direction of a vertical axis N of the lens optical region is set according to a predetermined function.
1. A progressive multifocal contact lens having a distance portion for aiding a far vision, a near portion for aiding a near vision, and an intermediate portion in which a power is changed progressively between the distance portion and the near portion, in a lens optical region,
so that said distance portion, said intermediate portion, and said near portion are arranged sequentially from one end to another end along a prescribed direction of said lens optical region;
a power distribution of said lens optical region along said prescribed direction is set according to the following formula (1); and
said prescribed direction is a vertical direction of an eye during wearing the progressive multifocal contact lens:
[
Formula
1
]
PowerDist
=
P
-
Power
+
(
Max
-
Add
π
)
{
tan
-
1
(
Wave
Bnf
X
-
Wave
)
+
tan
-
1
(
Wave
)
}
(
1
)
wherein each symbol in the formula (1) is defined as follows:
PowerDist: power distribution (unit: D (diopter));
P-Power: power (unit: D) at one end point of the lens optical region;
Max-Add: power difference (unit: D) between one end point and the other end point of the lens optical region;
Bnf: distance (unit: mm) from one end point of the lens optical region to a boundary between a distance power of the distance portion and a near power of the near portion;
Wave: power variation coefficient (wave degree); and
x: distance (unit: mm) from one end point of the lens optical region; wherein
−25D≦P-Power≦+25D;
±0D≦Max-Add≦+8D;
0.5 mm≦Bnf≦7 mm; and
1≦Wave≦8.
2. The progressive multifocal contact lens according to claim 1 , further comprising a rotation preventing mechanism of preventing a rotation of this lens, at an end part along the prescribed direction, said rotation preventing mechanism being a prism ballast provided at the other end side along the prescribed direction of the progressive multifocal contact lens.
3. The progressive multifocal contact lens according to claim 2 , wherein the power distribution according to the formula (1) is set along the prescribed direction of the lens optical region in one of the front surface and the back surface of said lens optical region, and the other of said from surface and back surface is formed to be a toric surface having an astigmatism correction function.
4. The progressive multifocal contact lens according to claim 1 , wherein the power distribution according to the formula (1) is set along the prescribed direction of the lens optical region in one of the front surface and the back surface of said lens optical region, and the other of said front surface and back surface is formed to be a toric surface having an astigmatism correcting function.
5. A progressive multifocal contact lens having a distance portion for aiding a far vision, a near portion for aiding a near vision, and an intermediate portion in which a power is changed progressively between the distance portion and the near portion, in a lens optical region,
so that said distance portion, said intermediate portion, and said near portion are arranged sequentially from one end to another end along a predescribed direction of said lens optical region;
a power distribution of said lens optical region along said prescribed direction is set according to the following formula (1); and
said prescribed direction is set so as to tilt toward a nose side of a face from the vertical direction of the eye during wearing the progressive multifocal contact lens:
[
Formula
1
]
PowerDist
=
P
-
Power
+
(
Max
-
Add
π
)
{
tan
-
1
(
Wave
Bnf
X
-
Wave
)
+
tan
-
1
(
Wave
)
}
(
1
)
wherein each symbol in the formula (1) is defined as follows:
PowerDist: power distribution (unit: D (diopter));
P-Power: power (unit: D) at one end point of the lens optical region;
Max-Add: power difference (unit: D) between one end point and the other end point of the lens optical region;
Bnf: distance (unit: mm) from one end point of the lens optical region to a boundary between a distance power of the distance portion and a near power of the near portion;
Wave: power variation coefficient (wave degree); and
x: distance (unit: mm) from one end point of the lens optical region; wherein
−25D≦P-Power≦+25D;
±0D≦Max-Add≦+8D;
0.5 mm≦Bnf≦7 mm; and
1≦Wave≦8.
6. The progressive multifocal contact lens according to claim 5 , further comprising a rotation preventing mechanism of preventing a rotation of this lens, at an end part along the prescribed direction, said rotation preventing mechanism being a prism ballast provided at the other end side along the predescribed direction of the progressive multifocal contact lens.
7. The progressive multifocal contact lens according to claim 5 wherein the power distribution according to the formula (1) is set along the prescribed direction of the lens optical region in one of the front surface and the back surface of said lens optical region, and the other of said front surface and back surface is formed to be a toric surface having an astigmatism correcting function.
8. The progressive multifocal contact lens according to claim 6 , wherein the power distribution according to the formula (1) is set along the prescribed direction of the lens optical region in one of the front surface and the back surface of said lens optical region, and the other of said front surface and back surface is formed to be a toric surface having an astigmatism correcting function.