JPH06317767A - Contact lens and its production - Google Patents

Abstract

PURPOSE:To improve the exchangeability of the tears existing between the contact lens and the cornea, to maintain the stable corrected sight and to adequately adjust the ratio of an area covering the cornea to enhance the feel of use by determining the outside diameter of the contact lens by the radius of curvature at the vertex of the inside surface. CONSTITUTION:This contact lens 1 consists of a convex outside surface 2, the concave inside surface 3 and a connecting surface 4 for connecting the outside surface 2 and the inside surface 3. The inside surface 3 is a part in contact with the human cornea and, therefore, corresponds to the shape of the cornea. The outside diameter of the contact lens 1 is determined from the average radius of curvature of the cornea in such a manner that the contact lens 1 adequately adjustable in the area covering the cornea is provided simply by measuring the average radius of curvature of the cornea of a wearing person by noticing the fact that the eyeball having the large cornea diameter has a tendency to the large average radius of curvature of the cornea as well. The average radius of curvature of the cornea is assumed to coincide with the radius BC of curvature at the vertex of the contact lens 1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to contact lenses. More specifically, the present invention relates to a contact lens that provides each wearer with a better wearing condition depending on the radius of curvature of the cornea.

[0002]

2. Description of the Related Art Conventionally, various shapes have been proposed in order to provide a contact lens wearer with a better wearing condition.

As used herein, providing a better wearing condition means improving the exchangeability of tear fluid existing between the contact lens and the cornea, which is required for corneal physiology, and providing stable corrected visual acuity. Is to provide.

For the purpose of (1), it has been often attempted to devise the shape of the peripheral portion of the contact lens. For example, as shown in FIG.
From 4 to the intermediate range portion 15 and the outer peripheral portion 16, the rear surfaces 11, 12, 13 are changed so that the radii of curvature R1, R2, R3 are sequentially increased (JP-A-60-11320).
No. 8). In this contact lens, the radius of curvature R1 of the rear surface 11 of the optical range portion is selected according to the eyeball of the individual, and based on this, the amount of tear fluid stored between the eyeball and the contact lens becomes appropriate, and the outer peripheral portion R2 and R3 so that the parts do not float and feel a foreign object.
Is determined within a certain range.

Further, even if the shape having the radius of curvature as described above is not formed, as shown in FIG.
The same effect as described above is obtained by extending the front surface 22 substantially obliquely from 3 to the front surface 22 (JP-A-57).
-181525)).

On the other hand, there is almost no technique devised in the wearing state for the purpose of 1), and rather, it is attempted to meet the purpose by accurately forming the shape of the optical surface of the contact lens as designed. Has been.

By the way, in the case of a general hard contact lens, it is said that a size that covers 45 to 65% of the area of the entire cornea is preferable to achieve the above-mentioned object. That is, as shown in FIG. 7, the contact lens 1 covering 65% or more of the entire area of the cornea is slow in movement on the cornea, impairs the circulation of tear fluid, and is supplied to the cornea via tear fluid. Since the amount of oxygen to be consumed is reduced and the portion which does not need to be covered is covered, it is difficult to discharge the metabolites, which is not preferable from the viewpoint of corneal physiology.

Further, as shown in FIG. 8, a contact lens having an area of 45% or less of the area covering the entire cornea has a large amount of movement due to a blink or the like, which deteriorates the stability of the visual acuity correction and gives a feeling of wearing. It is not preferable because it worsens.

Further, in order to provide a better wearing condition, a size which covers 50 to 60% of the entire area of the cornea is preferable.

[0010]

However, the size of the human eye (cornea) is different from each other, and in order to provide a contact lens in a good wearing condition as described above, the individual eye There is a problem in that size must also be considered. That is, when the contact lens 1 of the same size is worn by a person with small eyes, the area covering the cornea becomes large as shown in FIG. 7, which is not preferable due to reasons such as metabolism, and when the person with large eyes wears the contact lens 1, As shown in FIG. 8, the amount of movement is large, which is not preferable.

Therefore, attempts have been made to provide contact lenses having several kinds of outer diameters, but general contact lenses for correcting visual acuity have independent standards for the radius of curvature of the apex and the power. It is necessary to prepare a huge variety of contact lenses to add a standard for the outer diameter in addition to the adjustment, and there is a problem that it is very complicated and difficult for the prescriber and the manufacturer to manage. It was

In view of the above circumstances, the present invention has good exchangeability of tear fluid existing between the contact lens and the cornea, can maintain stable corrected visual acuity, and determines the apex curvature radius, the outer diameter corresponding to it. Since only one is determined, it is an object of the present invention to provide a contact lens which is a small standard product and which can appropriately adjust the ratio of the area covering the cornea to enhance the wearing feeling.

[0013]

The contact lens of the present invention comprises a convex outer surface, a concave inner surface corresponding to the shape of a human cornea, and a connecting surface connecting the outer surface and the inner surface. The outer diameter of the contact lens is determined by the radius of curvature of the apex of the inner surface.

Further, in the method for manufacturing a contact lens of the present invention, (a) an average radius of curvature of the cornea and an outer diameter are actually measured to obtain an equation showing a correlation, and (b) the inner surface of the contact lens with respect to the surface area S1 of the cornea. Determine the ratio K of the surface area S2,
(C) The surface area S1 of the cornea is a function of the average radius of curvature r of the cornea and the outer diameter 2d of the cornea, and the surface area S2 of the inner surface of the contact lens is the curvature radius BC of its apex and the outer diameter DIA.
Based on the fact that the radius of curvature BC of the apex of the contact lens matches the average radius of curvature r of the cornea, the outer diameter DIA of the contact lens is set to the average radius of curvature r of the cornea and the outer radius of the cornea. The diameter D of the contact lens is expressed as a function of the diameter K, and (d) the outer diameter D of the contact lens is calculated based on an equation showing the correlation between the average radius of curvature r of the cornea and the outer diameter 2D.
IA is represented as a function of the average radius of curvature r of the cornea and K, and (g) the average radius of curvature r of the cornea of the wearer is measured to determine the apex radius of curvature BC of the inner surface of the contact lens, The outer diameter DIA of the contact lens is also determined at the same time.

[0015]

EXAMPLES Examples of contact lenses of the present invention will be described below with reference to the accompanying drawings and tables.

FIG. 1 is a sectional view showing an example of the contact lens of the present invention, and FIG. 2 is a graph showing the relationship between the average radius of curvature of the cornea and the outer diameter measured.

In FIG. 1, the contact lens 1 comprises a convex outer surface 2, a concave inner surface 3 and a connecting surface 4 connecting the outer surface 2 and the inner surface 3. The inner surface 3 corresponds to the shape of the cornea because it is the portion that comes into contact with the human cornea. And
DIA represents the outer diameter of the contact lens 1, and BC represents the apex curvature radius of the inner surface 3.

In the contact lens of the present invention, attention is paid to the fact that an eyeball having a large corneal diameter tends to have a large average radius of curvature of the cornea, and only by measuring the average radius of curvature of the wearer's cornea, the area covering the cornea can be determined. It also seeks to determine the outer diameter of the contact lens from the average radius of curvature of the cornea so that a contact lens that can be properly adjusted can be provided. The average radius of curvature of the cornea was set to match the vertex radius of curvature (BC) of the contact lens 1.

FIG. 2 is a graph showing the average radius of curvature and outer diameter of the cornea of a large number of examiners, and the correlation between them. When the average radius of curvature is taken as the x-axis and the outer diameter is taken as the y-axis and a computer is used to regress to a linear equation, the following equation (1) is obtained.

Y = 1.03x + 3.71 (1) Here, the mean radius of curvature of the cornea is, as shown in FIG. 3, the radius of curvature D1 of the meridian (strong main meridian) in the direction of the smallest curvature, It is the average value (D1 + D2) / 2 of the radius of curvature D2 of the meridian (weak main meridian) in the direction with the largest curvature.

However, the purpose of regressing the linear equation is to represent it by the simplest equation possible, and the present invention is not limited to the above mathematical equation.

On the other hand, assuming that the shape of the cornea is a sphere, the surface area S1 of the cornea is r, where the average radius of curvature of the cornea is 2 and the outer diameter of the cornea is 2 × d.

[Equation 1] It is represented by.

Similarly, for the surface area S2 on the inner surface side of the contact lens mounted on the cornea, if the outer diameter of the contact lens is 2 × D,

[Equation 2]

Here, if the ratio of the area where the contact lens covers the cornea is K (%),

[Equation 3] Becomes

Therefore, when the equations (2) and (3) are introduced into the equation (4) to obtain the outer diameter 2 × D of the contact lens,

[Equation 4] Becomes

Further, from the equation (1), the average radius of curvature of the cornea x
, And the outer diameter y of the cornea, there is a relation of y = 1.03x + 3.71, so if we substitute x = r, y = 2d, we have a relation of 2d = 1.03r + 3.71. (5) Contact lens outer diameter 2
XD can be represented by the average radius of curvature r of the cornea and the parameter K. That is, the outer diameter of the contact lens 2 ×
D is a function of the average radius of curvature r and K of the cornea, and is expressed as 2D = 2f (r, K) (6), and the ratio K of the area covered by the contact lens to the cornea.
If the value of (%) is determined appropriately, the average radius of curvature r of the cornea
From this, the outer diameter of the contact lens, 2 × D, is determined.

Now, the apex curvature radius of the contact lens (B
Since C) is considered to be equal to the average radius of curvature r of the cornea, using r as the value of the radius of curvature of the apex (BC) in the above equation, the outer diameter of the contact lens covering the surface of the cornea at a desired ratio. (DIA) = 2 × D can be determined.

Example 1 FIG. 4 shows the radius of curvature of the apex (B
It is a graph which shows the relationship between C) and the outer diameter (DIA) of a contact lens. The straight line is a graph when the ratio K of the area where the contact lens covers the cornea is 60%, and the straight line is 55% and the straight line is 50%.

Next, the standard of the apex curvature radius (BC) and the outer diameter (DIA) of the contact lens determined on the basis thereof will be described.

Tables 1 to 4 show the types of DIA of contact lenses that are specified so that the radius of curvature (BC) of the apex changes at intervals of 0.05 mm. The unit of the vertex curvature radius (BC) of the existing contact lens is often 0.05 mm. However, as shown in Table 5, the vertex curvature radius (BC) may be set at 0.1 mm intervals.

Table 1 shows that the area of the contact lens covering the cornea is 55%, and the outer diameter of the contact lens (DI
A) was changed in units of 0.01 mm.

[0032]

[Table 1]

Further, as shown in Table 2, it is possible to change the outer diameter (DIA) of the contact lens in units of 0.2 mm. Even with such changes, many wearers will wear contact lenses whose covering area is between 45 and 65%.

[0034]

[Table 2]

Example 2 Further, in Tables 3 and 4, the ratio of the area where the contact lens covers the cornea is 50%, and the change in the outer diameter (DIA) of the contact lens is shown in Table 3 in 0.01 mm units. No. 4 is when performing in 0.3 mm units.

[0036]

[Table 3]

[0037]

[Table 4]

Example 3 In Table 5, the apex curvature radius (BC) is 0.1 mm, and the ratio of the area covered by the contact lens to the cornea is 60%.
The outer diameter (DIA) of the contact lens was changed in units of 0.2 mm.

[0039]

[Table 5]

The contact lens according to the present invention can be manufactured by general cutting or molding.

Further, the inner surface of the contact lens according to the present invention is not limited to the spherical shape, and an aspherical surface such as an elliptic surface can be adopted. That is, BC only refers to the apex curvature radius, and the apex curvature radius is present even on the elliptical surface that is intended to be more appropriately matched to the shape of the cornea, and the contact lens changes with the apex curvature radius change. It is also within the technology of the present invention to change the DIA of the above.

Further, in the present invention, although the outer surface shape is not described in detail, it is a shape that cooperates with the outer surface and the inner surface to form a desired dioptric power, and any shape that can be worn as a contact lens. It is also possible.

[0043]

In the contact lens of the present invention, the outer diameter is determined by the radius of curvature of the apex so that the area covering the cornea is appropriate. Therefore, the wearing condition is improved, and the type of contact lens held by the prescriber can be selected. The number can be reduced, and the management on the contact lens supply side and the manufacturing side can be facilitated.

Further, by measuring the average curvature of the cornea of the prescriber, the radius of curvature of the apex of the contact lens to be attached can be determined, and at the same time, the appropriate outer diameter (DIA) is also determined, which simplifies the prescription. Furthermore, the frequency of prescription replacement can be reduced.

[Brief description of drawings]

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

FIG. 2 is a graph showing the relationship between the average radius of curvature of the cornea and the outer diameter.

FIG. 3 is an explanatory diagram of an average radius of curvature of a cornea.

FIG. 4 is a graph showing the relationship between the apex curvature radius (BC) and the outer diameter (DIA) of a contact lens that covers the cornea at a desired ratio.

FIG. 5 is a cross-sectional view of a conventional contact lens.

FIG. 6 is a cross-sectional view of a conventional contact lens.

FIG. 7 is an explanatory diagram showing a state in which the contact lens is too large with respect to the size of the eyeball.

FIG. 8 is an explanatory diagram showing a state in which the contact lens is too small with respect to the size of the eyeball.

Claims (2)

[Claims] 1. A contact lens comprising a convex outer surface, a concave inner surface corresponding to the shape of a human cornea, and a connecting surface connecting the outer surface and the inner surface, wherein the outer diameter of the contact lens is an eyeball. The contact lens is determined by the radius of curvature of the vertex of the inner surface corresponding to. 2. A method of manufacturing a contact lens comprising a convex outer surface, a concave inner surface corresponding to the shape of a human cornea, and a connecting surface connecting the outer surface and the inner surface, comprising: (a)
The average radius of curvature of the cornea and the outer diameter are measured to obtain an equation showing the correlation, (b) the ratio K of the surface area S2 of the inner surface of the contact lens to the surface area S1 of the cornea is determined, and (c) the surface area S1 of the cornea is , The average radius of curvature r of the cornea and the outer diameter of the cornea 2
It is a function of d and is the surface area S of the inner surface of the contact lens.
2 is a function of the radius of curvature BC of the apex and the outer diameter DIA, and based on the fact that the radius of curvature BC of the apex of the contact lens matches the average radius of curvature r of the cornea, the outer diameter DIA of the contact lens is Is the average radius of curvature r of the cornea
And as a function of the outer diameter 2d of the cornea and the K,
(D) The outer diameter DIA of the contact lens based on the equation showing the correlation between the average radius of curvature r of the cornea and the outer diameter 2d.
Is expressed as a function of the average radius of curvature r of the cornea and K, and (g) by measuring the average radius of curvature r of the cornea of the wearer, the vertex radius of curvature B of the inner surface of the contact lens
C is determined and the outer diameter D of the contact lens is determined.
A method of manufacturing a contact lens, characterized in that IA is also determined at the same time.