JPH11242192A - Toric contact lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the stability of a lens without increasing a prism amount and an axial deviation by forming the front of the lens in a prism ballast shape, providing a continuously thin area from the upper side of the peripheral part of the lens to the lower side and providing a thin area of an aspherical shape on the lens upper part. SOLUTION: The front of a lens is formed in prism ballast shape, and the centroidal position of the lens is made eccentric from a geometric center, and the lens lower part 12 is made relatively thicker than the lens upper part 11. A continuously and relatively thin area 14 is provided from the lower side of the peripheral part 17 of the lens to the upper side, and a thin area 13 of the aspherical shape is provided on the lens upper part 11. Further, the width in the vertical direction of the thin area 13 of the aspherical shape is made larger than the width in the vertical direction of the relatively thin area 14 of the lower side of the lens peripheral part 17. Thus, the area of the lens upper part 11 is made large, and the thickness of the lens upper part 11 is made thin, and thus, the contact lens is stabilized on an eyeball without increasing the thickness of the lens lower part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact lens for correcting astigmatism, which can prevent rotation on an eyeball when worn. More specifically, the present invention relates to a toric contact lens having a good feeling of wearing while maintaining the stability of the lens even when the refractive power is large.

[0002]

2. Description of the Related Art Conventionally, when correcting astigmatism with a contact lens (hereinafter referred to as a lens), an ordinary hard contact lens (hereinafter referred to as an HCL) has generally been used. However, the HCL has problems such as insufficient correction of a patient with strong corneal astigmatism, and residual astigmatism when worn. Therefore, in recent years, research on toric contact lenses (hereinafter referred to as TCL) has been advanced as a contact lens dedicated to correcting astigmatism to compensate for these drawbacks. Here, the TCL refers to a lens having a spherical refractive power and a cylindrical refractive power on the front surface, the rear surface, or both surfaces of the lens.

What is important in TLC is to stabilize the astigmatic axis of the lens on the eyeball. That is, since a lens generally rotates on the eyeball, a lens having a directionality such as an astigmatic axis such as TLC cannot obtain good visual acuity if the lens rotates on the eyeball. is there. For this reason, various methods have been studied for controlling the rotation of the TCL on the eyeball. For example, a prism ballast type TCL has been proposed in which the center of gravity of the lens is decentered from the geometric center, and the thickness of the lower portion relative to the upper portion of the lens is continuously increased. This is to stabilize by the difference in the relative thickness of the lens part. In the case of this type of TCL, determination of the prism amount is important. That is, the prism amount increases as the eccentric amount of the lens increases and the refractive power of the lens increases. For the stability of the lens, the larger the prism amount, the better, but there is a limit in practical use from the viewpoint of wearing feeling and lens design.

As a means for imparting a prism to a lens, there is a method of providing a so-called offset amount X, which shifts the central axis of the rear surface 26 of the lens and the central axis of the front surface 25 as shown in FIG. The offset amount X may be expressed by a shift amount or a shift ratio. When the offset amount X is constant, the amount of eccentricity decreases when the refractive power of the lens is increased, so that the stability is obtained without increasing the prism amount. Did not.

That is, as described above, a drawback of the prism ballast type TCL is that the greater the refractive power of the lens, the worse the stability of the lens. Therefore, the mainstream well-known technologies currently used for TCL include:
As shown in FIGS. 8 and 9, a thin region 33 that has been subjected to slab-off processing is provided from the upper side to the lower side of the peripheral portion 37 of the above-mentioned prism-palast type TCL, so that not only the weight of the prism but also the lens portion Are stabilized by the difference in the relative thicknesses.

In Japanese Patent Application Laid-Open No. 6-34920, as a technique for providing stability while reducing the amount of prism, attention is paid to the relationship between the amount of prism and the deviation rate of the axis. In the TCL provided with, a technology in which the axis deviation rate is set to a specific amount is disclosed.

[0007]

The disadvantage of the prism ballast type TCL is that the greater the refractive power of the lens, the worse the stability of the lens. As a remedy for this disadvantage, a lens having a large refractive power is required to have an offset amount X
There is a method of increasing the amount of eccentricity to increase the amount of eccentricity and impart stability to the lens. However, in this method, the thick part of the ballast becomes extremely large, which is not preferable in terms of wearing feeling and supply of oxygen to the eyes.

In the conventional method of performing slab-off processing from the upper part to the lower part of the peripheral part 37 of the prism ballast type TCL, in the case of a lens having a large refractive power, the radius of curvature 21 and 22 of the optical surface becomes large. 35
A boundary line 36 between the lens optical unit 35 and the lower thin region 33 becomes thicker.
Since the ratio of the difference in thickness from 6 ′ was small, the lens stability could not be sufficiently maintained. As a solution to this problem, there is a means for increasing the offset amount in order to increase the prism amount.
The thickness of 6 'was further increased, and there was a problem in wearing feeling and the like.

On the other hand, the amount of axis deviation of the toric contact lens disclosed in Japanese Patent Application Laid-Open No. 6-34920 is determined by a specific amount (2.5 to
7.5%, for example, for a 14 mm diameter lens, 0.35
1.05 mm. ) Range,
Since the offset amount is large, it is considered that the thin region at the top becomes narrow and the thickness of the boundary line between the thin region at the bottom and the optical unit becomes large.There is no limit to the method of adjusting the prism amount by the offset amount. Was.

According to the present invention, in order to solve the above problems, it is possible to improve the stability of a lens without increasing the amount of prism and the amount of displacement of an axis, and to provide a good feeling of wearing even a lens having a large refractive power. An object of the present invention is to provide a toric contact lens having the same.

[0011]

In order to solve the above-mentioned problems, a toric contact lens according to the present invention is a contact lens having a front surface in the form of a prism ballast, which is continuous from the upper side to the lower side of the peripheral portion of the lens. It is characterized in that an extremely thin region is provided, and a thin region having an aspherical shape is provided above the lens.

The aspherical thin region provided above the lens has a toroidal surface shape. Further, the vertical width of the thin region having the aspherical shape is larger than the vertical width of the relatively thin region below the peripheral portion of the lens. In addition, in the prism ballast shape, the central axis of the optical part on the front surface is shifted from the geometric central axis on the rear surface by 0.10 to 0.30 mm.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments shown in the drawings. FIG. 1 is a front view of the toric contact lens of the present invention, and FIG. 2 is a cross-sectional view taken along the center line of the lens. In the toric contact lens of the present invention, the front surface 5 has a prism ballast shape,
The position of the center of gravity of the lens is decentered from the geometric center, and the lower part 12 of the lens is relatively thicker than the upper part 11 of the lens. In addition, from the lower side to the upper side of the peripheral portion 17 of the lens, a relatively thin region 1 is continuously formed by slab-off processing.
4 are provided. Further, a thin region 13 having an aspherical shape is provided on the upper portion 11 of the lens.

The vertical width of the thin region 13 having an aspherical shape is larger than the vertical width of the relatively thin region 14 below the lens peripheral portion 17. This allows
Since the area of the lens upper portion 13 can be increased, the thickness of the lens upper portion 11 can be reduced, and as a result, the contact lens can be stabilized on the eyeball when the contact lens is mounted without increasing the thickness of the lens lower portion 12. That is, the thin region 13 having an aspherical shape is wider than the relatively thin region 14 below the lens peripheral portion 17, so that the upper part 11 of the lens is formed.
Becomes thinner. For example, in the case of a lens having a diameter of 14 mm, a so-called offset amount X for shifting the central axis of the rear surface 6 of the lens and the central axis of the front surface 5 is set to 0.10 to 0.3.
It can be set within 0 mm, preferably 0.15 to 0.25 mm, so that a sufficient amount of prism can be obtained and stability can be maintained.

Further, it is preferable that the shape of the thin region 13 which is an aspheric surface is a toroidal surface shape. Here, the toroidal surface refers to a surface in which the length of the radius of curvature in the vertical direction and the length of the radius of curvature in the horizontal direction perpendicular to each other are different from each other. Since the shape of the thin region 13 having an aspherical surface shape is a toroidal surface shape, the thin region 13 having a toroidal surface shape is formed.
, The radius of curvature 3 in the horizontal direction and the radius of curvature 4 in the vertical direction can be arbitrarily specified. That is, this makes it possible to adjust the processing shape of the thin region 13 having the toroidal surface shape to an arbitrary shape.

Since the toric contact lens of the present invention is configured as described above, the area of the thin region 13 having an aspherical shape can be adjusted. It is not necessary to increase X, and as a result, the thickness of the lens lower portion 12 can be reduced. That is, a lens with good stability can be obtained only by adjusting the area of the thin region 13 having an aspherical shape.

The upper portion 11 of the toric contact lens of the present invention has a thin region 13 having a toroidal surface shape. The lower optical portion 15 has a lateral curvature radius 1 and a thin toroidal surface shape. The difference in the radius of curvature 3 in the lateral direction of the region 13 causes a difference in the slab-off processing shape. This difference is illustrated in FIGS. That is, FIG. 3 shows a case where the radius of curvature 1 in the horizontal direction is larger than the radius of curvature 3, and the boundary 16 between the thin region 13 having the toroidal surface shape of the toric contact lens and the lower optical unit 15 is in the vertical direction. The curve has a radius of curvature of 2, 4 as an axis, and has a downward curve with respect to the axis. FIG. 4 shows a case where the curvature radius 1 and the curvature radius 3 in the horizontal direction are equal, and the boundary 16 of the toric contact lens is a straight line orthogonal to the curvature radii 2 and 4 in the vertical direction. FIG. 5 shows a case where the radius of curvature 1 in the horizontal direction is smaller than the radius of curvature 3;
The boundary line 16 of the toric contact lens has a vertical curvature radius of 2, 4 as an axis, and is a curved line upward with respect to the axis. It should be noted that, although it depends on the refractive power of the lens, the shape of the cornea of the wearer, and the intraocular pressure, the shapes shown in FIGS.

Further, as described above, the toric contact lens of the present invention has a relatively thin region 14 which has been subjected to slab-off processing from the lower side of the peripheral portion 17 of the lens to the upper side of the lens, and has an aspherical surface on the upper portion 11 of the lens. By providing a thin region 13 having a shape and being a toroidal surface shape, the processing shape of the thin region 13 having a toroidal surface shape can be adjusted to an arbitrary shape, and it can be applied to a lens for oblique astigmatism. it can. That is, the lens for oblique astigmatism refers to a lens in which the radii of curvature 1 and 2 orthogonal to the lower optical unit 15 are inclined obliquely with respect to the position of the center of gravity of the lens.
This is shown in FIG. With such a configuration, the shape of the thin region 13 having the toroidal surface shape can be arbitrarily adjusted, and the thin region 13 having the toroidal surface shape can always be located on the upper portion 11 of the lens. Therefore, even in the case of a lens for oblique astigmatism, a lens with a stable axialness can be obtained.

In this embodiment, the thin region 13 having an aspherical surface has a toroidal surface shape.
May be an ellipsoidal shape or a parabolic shape since it may be an aspherical shape.

Next, an embodiment will be described based on the embodiment shown in FIG. First, the vertical width of the thin region 13 having an aspheric shape is set to 3.0 mm, and the lens peripheral portion 1 is formed.
7, the width of the relatively thin region 14 in the vertical direction is 2.4 m.
m. Also, the lower optical unit 1 in this embodiment
5 was processed with a radius of curvature 1 in the horizontal direction of 9.75 mm and a radius of curvature 2 in the vertical direction of 10.18 mm. In addition, the radius of curvature 3 in the lateral direction of the thin region 13 having an aspherical shape is set to 9.
It is processed at 75 mm and a radius of curvature 4 in the vertical direction of 9.96 mm. Further, by setting the diameter of the lens to 14.00 mm, the offset amount X becomes 0.20 mm.
Therefore, the offset amount X is within 0.10 to 0.30 mm, a sufficient prism amount can be obtained, and stability can be maintained.

[0021]

As described above, the toric contact lens of the present invention is a contact lens having a prism ballast shape on the front surface, and has a continuously thin region from the upper side to the lower side of the peripheral portion of the lens. In addition, since the thin region having the aspherical shape is provided on the upper portion of the lens, the area of the thin region having the aspherical shape can be adjusted, and even if the lens has a high refractive power, the offset amount is increased. There is no necessity, and as a result, the thickness of the lower part of the lens can be reduced. That is, there is an effect that a lens with good stability can be obtained only by adjusting the processing area of a thin region having an aspherical shape.

Further, since the thin region having an aspherical shape provided on the upper portion of the lens has a toroidal surface shape, the lateral and vertical curvature radii of the thin region having the toroidal surface shape can be arbitrarily set. Can be specified.
That is, this makes it possible to adjust the processing shape of the thin region that is a toroidal surface shape to an arbitrary shape, and it can be applied to a contact lens having a large refractive power and a contact lens for oblique astigmatism. It has the effect of being functional.

Further, the vertical width of the thin region having the aspherical shape is larger than the vertical width of the relatively thin region below the peripheral portion of the lens. The thickness of the upper part of the lens can be reduced without increasing the amount of prism, and as a result, the amount of displacement of the axis can be minimized, and the contact lens can be stabilized on the eyeball when the contact lens is mounted without increasing the amount of prism It has the effect of.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the toric contact lens of the present invention.

FIG. 2 is a sectional view of the embodiment shown in FIG. 1 taken along a lens center line.

FIG. 3 is a front view showing another embodiment different from the embodiment of FIGS. 1 and 2;

FIG. 4 is a front view showing another embodiment different from the embodiment of FIGS. 1 to 3;

FIG. 5 is a front view showing another embodiment different from the embodiment of FIGS. 1 to 4;

FIG. 6 is a front view showing an example of a contact lens for oblique astigmatism.

FIG. 7 is a front view of a conventional prism ballast type contact lens.

FIG. 8 is a front view of another prism ballast type contact lens different from FIG. 7;

FIG. 9 is a sectional view taken along the center line of the lens shown in FIG. 8;

[Explanation of symbols]

 1, 2, 3, 4 Radius of curvature 5 Front surface 6 Rear surface 11 Upper lens portion 12 Lower lens portion 13 Thin region having an aspherical shape 14 Relatively thin region 15 Optical portion 16 Boundary line 17 Peripheral portion X offset amount

Claims (4)

[Claims] 1. A contact lens having a prism ballast shape on the front surface, wherein a thin region is continuously provided from the upper side to the lower side of the peripheral portion of the lens, and the lens is aspherical on the upper portion of the lens. A toric contact lens characterized by having an area. 2. The toric contact lens according to claim 1, wherein the aspherical thin region provided above the lens has a toroidal surface shape. 3. The vertical width of the thin region having the aspherical shape is larger than the vertical width of the relatively thin region below the peripheral portion of the lens. Toric contact lens. 4. In the above-mentioned prism ballast shape, the central axis of the optical part on the front surface is defined by the geometric central axis on the rear surface,
The toric contact lens according to any one of claims 1 to 3, which is shifted by 0.10 to 0.30 mm.