JP2008090103A - Contact lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens which can cope with corneas of aspherical shapes in complex cases, such as keratoconus, and corneal irregular astigmatism, having intricately changing corneal shapes, and which is easy to design and manufacture. <P>SOLUTION: One or both of a lens inner surface and lens outer surface comprises a substantially circular lens optical region 1 and at least one annular peripheral region 2 continuous with the outer side of the lens optical region. In addition, when the diametric direction sectional plane of the lens is viewed, the curve forming the lens optical region is formed of a plurality of arcuate portions 3 to 5, respectively varying in curvature connected tangent to each other. At the connection points P<SB>1</SB>to P<SB>3</SB>of the arcuate portions, the center O<SB>n</SB>of the circle, corresponding to the arcuate portion on one side, is arranged in a position existing on the radius of curvature r<SB>n-1</SB>of the arcuate portion on the other side and is deviated from the center O<SB>n-1</SB>of the circle, corresponding to the arcuate portion on the other side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a contact lens, and more particularly, to a structure of an optical region on the lens inner surface and rear surface of a contact lens.

Since the cornea is an avascular tissue, oxygen supply to the cornea becomes a problem when a hard contact lens is attached to the cornea. This oxygen supply is caused by oxygen permeating through the lens material or blinking. When the contact lens moves on the cornea, tear fluid interposed between the lens and the cornea is exchanged in the lens inner surface region. And in order to wear a contact lens comfortably, the contact lens of the design suitable for the cornea shape is calculated | required.

The cornea generally has an aspherical shape in which the curvature gradually changes from the central part toward the peripheral part, but the degree of change varies depending on the person, such as keratoconus, corneal irregular astigmatism, etc. In this case, the aspheric shape of the cornea is more complicated than that of the general cornea.
For this reason, when a conventional spherical lens is used for cases such as keratoconus and irregular corneal astigmatism, the difference in curvature between the central portion and the peripheral portion of the cornea may cause an unpleasant wearing feeling, and the lens may be displaced or dropped out. . In addition, in a contact lens in which the inner and outer surfaces of the lens are formed by a curve calculated based on a single cone coefficient, the shape of the transition portion of the lens curvature is determined by the cone coefficient, so the complex aspheric shape of the cornea Could not cope with.

As a conventional technique for solving the above-mentioned drawbacks, an outer surface, an inner surface and a base are provided, the inner surface and the outer surface each have a central optical part and an outer keratoconus, and the inner surface has a common center point on the inner surface of the lens. Divided into a plurality of local surface segments by a plurality of radially extending borders starting from each of the local surface segments, each of which corresponds to the corresponding local surface portion of the cornea under each local surface segment when the lens is mounted There is a contact lens that conforms to the shape (see Patent Document 1).
However, since this contact lens is formed by a combination of aspheric surfaces having different conic coefficients, it has a drawback that the calculation of the lens structure becomes complicated.

In addition, a concentric single viewpoint lens is known in which a ray passing through the periphery of the lens is focused on the same focal plane as a ray passing through the center of the lens to improve the quality of the lens image and improve the depth of focus ( Patent Document 2). In this lens, the inner surface of the lens is configured by combining a spherical surface having a coordinate center on the optical axis at the center of the lens. In this case, the inner surface of the lens is bent at the junction of a plurality of spherical surfaces and a spherical surface. It has the drawback that it causes a point and causes a physical irritation to the eye during wearing, which hinders comfortable wearing. For this reason, a plurality of steps for smoothing the bending point are required at the time of manufacturing the lens, and there is a problem that the manufacturing process becomes complicated and the cost is high.

JP 2001-502810 A JP-A-8-338969

  Therefore, an object of the present invention is to provide a lens that can cope with a keratoconus whose corneal shape changes in a complicated manner and a complex aspherical cornea in cases such as corneal irregular astigmatism, and that is easy to design and manufacture. .

  In order to solve the above-described problem, according to the present invention, one or both of the lens inner surface and the lens outer surface is a substantially circular lens optical region, and at least one annular peripheral region continuous to the outside of the lens optical region; And a curve forming the lens optical region is formed by connecting a plurality of arc portions having different curvatures so as to be tangent to each other when the cross section in the diameter direction of the lens is viewed. At the connection point, the center of the circle corresponding to the arc portion on one side is located on the curvature radius of the arc portion on the other side and is shifted from the center of the circle corresponding to the arc portion on the other side. The contact lens is characterized by being a thing.

Further, in the above configuration, it is preferable that the curve forming the lens optical region is formed so as to be bilaterally symmetric with respect to the central axis of the lens when the diametrical cross section of the lens is viewed.
Further, when the cross section in the diametrical direction of the lens is viewed, the radius of curvature of the adjacent arc portion may gradually increase from the center to the peripheral portion, or may be configured to gradually decrease. Alternatively, the curvature radius may be increased or decreased irregularly.

According to the present invention, the lens optical region is formed by providing a spherical structure with an arbitrary radius of curvature successively from the lens center to the radially outer side on one or both of the inner and outer surfaces of the lens according to the corneal shape. Since the spherical surfaces having arbitrary radii of curvature that are successively consecutive are tangent to each other by simple calculation, it is possible to design a contact lens suitable for a cornea having a complicated aspherical shape. In addition, in this case, the refractive power can be easily calculated for each spherical structure forming the lens optical region, and thus the refractive power of the lens can be adjusted very easily.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1A is a plan view of a contact lens according to one embodiment of the present invention. Referring to FIG. 1A, a contact lens according to the present invention has an annular inner surface and / or an outer surface of a lens in which a lens optical region 1 having a substantially circular shape and a lens optical region 1 are sequentially continuous to the outside of the lens optical region 1. It consists of a peripheral area (bevel area) 2. The lens optical region 1 further includes a circular central zone I, an annular first peripheral zone II that continues to the outside, and a second peripheral zone III that continues to the outside. Then, when the cross section in the diameter direction of the lens is viewed, the curve forming the lens optical region is formed so as to be symmetrical with respect to the central axis of the lens.

FIG. 1B is a cross-sectional view in the lens diameter direction for explaining the configuration of the lens optical region on the inner surface of the contact lens shown in FIG. As described above, in this embodiment, when the diametrical cross section of the lens is viewed, the curve constituting the lens optical region is symmetrical with respect to the central axis 6 of the lens. ), Only the right half of the lens center axis 6 is shown.

Referring to FIG. 1B, according to the present invention, the lens optical region 1 corresponds to the central zone I, the first peripheral zone II, and the second peripheral zone III when the diametrical cross section is viewed. The three arc portions 3, 4 and 5 having different curvatures are connected so as to be tangent to each other. At the connection points P ₁ , P ₂ , and P ₃ of the arc portions 3, 4, and 5, the center of the circle corresponding to the arc portion on one side is on the radius of curvature of the arc portion on the other side, and It is arranged at a position shifted from the center of the circle corresponding to the arc portion. In this case, depending on the shape of the cornea in which the lens is worn, the radius of curvature of the adjacent arc portion gradually increases from the center toward the periphery when the diametrical cross section of the lens is viewed, or gradually. You may comprise so that it may become small, or you may comprise so that the increase / decrease in this curvature radius may occur irregularly.

Describing the above configuration geometrically, xy coordinates with the lens center as the origin are set, and the coordinates of the center of the circle corresponding to the arc portion (curvature radius r (n)) of an arbitrary n-th zone are set. O _n (O _x (n), O _y (n)), and the coordinates of the intersection of the arc portion of the (n−1) th zone and the arc portion of the nth zone are P _n (x (n), y ( n)), the coordinates of the center of the circle corresponding to the arc portion of the (n-1) th zone are O _n-1 (O _x (n-1), O _y (n-1)), and the radius is r (n -1), and θ (n) is the angle between the straight line O _n-1 -P _n and the y axis,

が成立する。

Is established.

From the equations (1) and (2),
O _x (n) = x (n) −r (n) × sin (θ (n))
O _y (n) = y (n) + r (n) × cos (θ (n))
Is derived. Based on this equation, the center coordinates of the circle corresponding to the arc portion of the nth zone of the optical region are determined, and the arc portion of each zone is sequentially designed accordingly.

Next, the contact lens according to the present invention was actually designed and manufactured, and the state of the lens, the feeling of wearing, etc. when the lens was actually worn on the patient's eye were examined.
(Example 1)
The cornea is measured with a cornea shape measuring device (PR-7000; manufactured by Sun Contact Lens Co., Ltd.), and is suitable for a cornea having a radius of curvature at the center of the cornea = 7.71 mm and a cone coefficient of a conicoid curve = −0.36. Designed and manufactured a single-focus contact lens. In this case, the relationship between the distance from the center of the cornea and the radius of curvature thereof was obtained from the corneal shape measurement data as shown in Table 1.

The refractive power of the lens = −3.00 D, the thickness of the lens = 0.14 mm, the material refractive index = 1.5, and the lens size = 8.8 mm. And on both the inner and outer surfaces of the lens, the lens optical region comprises a circular central zone I, an outer annular first peripheral zone II, and an outer annular second peripheral zone III; By making the width of each zone the same on the inner and outer surfaces of the lens, and calculating the radius of curvature of each zone of the optical region of the lens outer surface from the radius of curvature of each zone of the optical region of the lens inner surface and the target lens refractive power, Contact lenses were produced with the numerical values shown in Table 2. In Table 2, it should be noted that the width of the central zone of the inner and outer surfaces of the lens is not the entire width, but the width from the center of the central zone to the boundary with the first peripheral zone (about this) The same applies to Examples 2 and 3 below).

FIG. 2 shows a cross section in the diameter direction of the produced contact lens. In FIG. 2, 10 is a lens central axis, 11 is a lens inner surface, 12 is a lens outer surface, and IV is a bevel region.
A conventional spherical lens with an inner radius of curvature of 7.75 mm, selected as the best lens from the manufactured lens and trial lens (lens wearing state evaluation lens), respectively, to an eye with a corneal radius of curvature = 7.71 mm We compared wearing position of lens, movement of lens, and feeling of wearing. As a result of comparison, the lens of the present invention was superior in all of the lens stationary position, lens movement, and wearing feeling.

(Example 2)
A bifocal contact lens compatible with the cornea as in Example 1 was produced.
The distance refractive power of the lens = −3.00 D, the near refractive power = −1.00 D, the lens thickness = 0.14 mm, the material refractive index = 1.5, and the lens size = 8.8 mm. And on both the inner and outer surfaces of the lens, the lens optical region comprises a circular central zone I, an outer annular first peripheral zone II, and an outer annular second peripheral zone III; By making the width of each zone the same on the inner and outer surfaces of the lens, and calculating the radius of curvature of each zone of the optical region of the lens outer surface from the radius of curvature of each zone of the optical region of the lens inner surface and the target lens refractive power, Contact lenses were designed and fabricated with the values shown in Table 3.

FIG. 3 shows a diametrical cross section of the produced contact lens. In FIG. 3, 20 is a lens central axis, 21 is a lens inner surface, 22 is a lens outer surface, and IV is a bevel region.
A lens and a trial lens (lens wearing state evaluation lens) according to this example are used for an eye whose spectacle correction power is far vision = −3.00D, near vision = −1.00D, and corneal curvature radius = 7.71 mm. A commercially available bifocal lens with an inner radius of curvature of 7.75 mm, which was selected as the best lens, was worn, and the lens stationary position, lens movement, and appearance were compared. The lens according to the present invention was superior in terms of lens stationary position, lens movement, and appearance.

(Example 3)
A single-focus contact lens suitable for a cornea such as a keratoconus having a large difference between the radius of curvature at the central portion of the cornea and the radius of curvature at the peripheral portion was prepared. When the cornea of a medium keratoconic eye was measured with a cornea shape measuring device (PR-7000; manufactured by Sun Contact Lens Co., Ltd.), the relationship between the distance from the cornea center and the radius of curvature was determined from the data. It was like 4.

The refractive power of the lens = −3.00 D, the thickness of the lens = 0.14 mm, the material refractive index = 1.5, and the lens size = 8.8 mm. Then, on both the inner surface and the outer surface of the lens, the lens optical region is divided into a circular central zone I, an outer annular first peripheral zone II, an outer annular second peripheral zone III, an outer annular first zone. 3 peripheral zones IV and an annular fourth peripheral zone V outside thereof, and the width of each zone is the same on the inner and outer surfaces of the lens, and the radius of curvature of each zone in the optical region of the lens inner surface and the target lens By calculating the radius of curvature of each zone of the optical region on the outer surface of the lens from the refractive power, a contact lens was designed and manufactured with the numerical values shown in Table 5.

FIG. 4 shows a cross section in the diameter direction of the produced contact lens. In FIG. 4, 30 is a lens central axis, 31 is a lens inner surface, 32 is a lens outer surface, and VI is a bevel region.
For a medium keratoconus eye whose corneal shape was measured, a conventional corneal eye with a radius of curvature of 7.60 mm was selected as the best lens from the lens according to this example and a trial lens (lens for lens wearing condition evaluation). A spherical lens was worn, and the lens rest position, lens movement, and wearing feeling were compared.
The lens according to the present invention was superior in terms of the lens stationary position, lens movement, and wearing feeling, and was more suitable for the corneal shape.

(A) is a plan view of a contact lens according to one embodiment of the present invention, (B) is a lens diameter direction explanation of the configuration of the lens optical region of the lens inner surface of the contact lens shown in (A) It is sectional drawing. 2 is a diametrical cross section of a contact lens manufactured in Example 1. FIG. 3 is a cross section in the diameter direction of a contact lens produced in Example 2. 3 is a cross section in the diameter direction of a contact lens manufactured in Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens optical area | region 2 Peripheral area | region I Central zone II 1st peripheral zone III 2nd peripheral zone 3, 4, 5 Arc part 6 Lens central axis

Claims (2)

  When one or both of the lens inner surface and the lens outer surface is composed of a substantially circular lens optical region and at least one annular peripheral region continuous to the outside of the lens optical region, and the diametrical cross section of the lens is viewed Further, the curve forming the lens optical region is formed by connecting a plurality of arc portions having different curvatures so as to be tangent to each other, and a circle corresponding to one arc portion at the connection point of the arc portions. The contact lens is located on a radius of curvature of the arc portion on the other side and is displaced from the center of the circle corresponding to the arc portion on the other side. The curved line forming the lens optical region is formed so as to be bilaterally symmetric with respect to the central axis of the lens when the cross section in the diameter direction of the lens is viewed. The contact lens described.

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