JPH112786A - Contact lens and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable industrial mass production of contact lenses which are excellent in lacrimal fluid exchange, excellent in wear feel and good in the safety of the eyes by forming a rear face corresponding to the plural segmental polynominals formed by the segmental polynomials which approximate the lens shape in the adjacent segments joined at the data points and form the segmental polynominals equal in first derivatives at the data points. SOLUTION: The contact lens 2 rides on the surface of the cornea 1 via the layer of the lacrimal fluid and the rear face thereof comprises a curve 3 forming an optical part 5, a curve 4 forming a peripheral part 7 and a curve forming a joint part 6 of the optical part 5 and the peripheral part 7 and accelerating the lacrimal fluid exchange. The shape of the rear face of the lens may be indicated as the point sequence data expressed by the X-axis and Y-axis coordinates having the center of the lens rear face as its base point. The number of the point sequence data is optionally settable and the optimum data set may be determined by repeating the addition or deletion while checking the display of the segmental polynominals functions. The rear face of the lens is formed by executing cutting in accordance with such data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the design of a contact lens, and more particularly to the design of a posterior surface of a contact lens in contact with a cornea. The shape of the cornea of a normal person is not spherical, but has a curvature that flattens from the center to the periphery, and a shape whose absolute value and rate of change differ in the vertical and horizontal directions. And the rate of change are different. In the prescription of a contact lens, a lens having a posterior curve corresponding to such a complicated corneal shape is selected, and a blinking motion is performed on the cornea smoothly in the vertical direction by blinking of the eye, so that a lens between the lens and the cornea is formed. The lacrimal fluid is exchanged, the lacrimal fluid containing waste products and cell debris from the ocular cells flows out, and the fresh lacrimal fluid containing oxygen flows in, thereby maintaining the normal physiological activity of the ocular cells. Also, due to its soft properties, soft contact lenses cause pumping movement of the lenses due to blinking of the eyes, thereby performing tear exchange. Therefore, the posterior design of contact lenses is extremely important for maintaining eye health.

[0002]

2. Description of the Related Art Conventionally, in order to achieve this object, an optical unit having a curvature close to the curvature of the central part of the cornea has been provided, and an optical unit for ensuring smooth lens movement and improving tear exchange. Lenses having perimeters with larger curvatures have been produced. However, the joint between the two curved surfaces is formed by a polishing operation, and the shape varies. In addition, quality control is difficult in mass production on an industrial scale, and the shape of the joint cannot be controlled uniformly.

For the purpose of solving this, for example, Japanese Patent Application Laid-Open No.
Although a method described in Japanese Patent No. 500973 has been developed, this method is a method for producing a contact lens that fits the shape of the cornea, and a part that plays an important role in tear exchange,
That is, the junction between the optical part and the peripheral part is also a contact lens corresponding to a piecewise polynomial (for example, a spline) approximating the shape along the cornea shape, so that the clearance between the cornea and the cornea is too small to exchange tear fluid. turn into.

[0004]

SUMMARY OF THE INVENTION A large number of industrially manufactured contact lenses having a posterior surface design of a contact lens almost in line with the shape of the cornea, excellent in tear exchange, excellent in wearing feeling, and excellent in eye safety. Supply.

[0005]

According to the present invention, a design of a junction between an optical portion of a contact lens and a peripheral curve, which plays an important role in tear exchange, is digitized and stored as data.
The data is combined with the corneal shape data of the contact lens wearer, a segmental polynomial is generated based on these data, and a contact lens having a posterior surface of the contact lens designed by the segmental polynomial is provided.

That is, the present invention relates to a contact lens having a surface conforming to the shape of the cornea and having a curved surface shaped to promote lacrimal fluid exchange, the data representing the shape of the cornea, and the posterior surface of the cornea and the contact lens. From the point sequence data representing the shape of the back surface of the contact lens obtained from the data representing the distance to the lens, and from the point sequence data representing the shape that promotes tear exchange, the lens shape at the adjacent sections joined at these data points Produces a piecewise polynomial in which the first derivative is equal at that data point,
An object of the present invention is to provide a contact lens having a rear surface corresponding to the plurality of segmented polynomials.

[0007] Data representing the shape of the cornea is Platinide-
Keratometer, ophthalmometer, photokeratometer,
It is determined by a video keratometer, a corneal morphological analyzer with a built-in computer, and the like. Particularly, a corneal morphological analyzer such as a photokeratometer and a video keratometer is preferable because the radius of curvature of each part of a wide range of the cornea can be determined. The data is obtained from the radius of curvature at each position of the cornea measured by these devices, the sagittal depth at each position (x-axis in FIG. 5) starting from the center of the cornea (y-axis in FIG. 5, where (The origin of the y-axis in FIG. 5 is the rear surface of the lens).
Normally, a contact lens is constituted by a plane having the optical center as the center of rotation, and from the data obtained at each position of the cornea obtained above, a fixed interval (for example, 1 mm) from the center of the cornea as a starting point
Is approximated by calculating the average value at each concentric circle position.

The data representing the distance between the cornea and the posterior surface of the contact lens is empirically determined by the prescription of the contact lens, and the distance is determined from the intensity distribution of a fluorescein solution between the cornea and the contact lens. Can be The appropriate interval varies depending on the position of the contact lens, and the appropriate interval differs depending on the position of the contact lens, and there are people with refractive errors such as corneal astigmatism, and it is not possible to determine this appropriate value in a straightforward manner, but when performing general vision correction Is about 2-200μ
m, which is often small at the center of the lens and large at the periphery.

Point sequence data representing the shape of the rear surface of the contact lens is obtained by adding the data of the distance between the cornea and the rear surface of the contact lens to the data of the corneal shape,
It is represented by coordinates with the center point of the contact lens as a base point. For example, when the radial direction of the lens is the x axis and the optical axis direction of the lens is the y axis, (x0, y0), (x1, y1) ·
.. (Xn, yn), representative examples of which are points 30 (x30, y30) and 32 (x32, y) in FIG.
32) and point 34 (x34, y34). The point sequence data representing the shape that promotes tear exchange is based on the prescription of a lens that has been processed by polishing the joint between the optical part curve and the peripheral curve on the rear surface of the lens for the contact lens wearer, and the movement of the contact lens, tear exchange It is obtained by empirically selecting the optimal lens from clinical data such as speed and wearing feeling, and measuring the rear shape of the lens with a measuring instrument such as a bevel analyzer or a precision shape measuring instrument.

FIG. 5 shows a specific example of the contact lens of the present invention.
It was shown to. In FIG. 5, the contact lens 2 rides on the surface of the cornea 1 via a layer of tear fluid, and the rear surface has a curve 3 forming an optical portion 5, a curve 4 forming a peripheral portion 7,
And a curve that promotes tear exchange to form a joint 6 between the optical part and the peripheral part. This lens rear surface shape is represented by point sequence data represented by x-axis and y-axis coordinates with the center of the illustrated lens rear surface as a base point, for example,.
30, x30) ... (x32, y32) ... (x
34, y34). In FIG. 5, the outermost part (x30, y30) of the optical part, the outermost part (x32, y32) of the tear exchange promoting part, and the outermost part (x
34, y34), the number of point sequence data can be set arbitrarily, and addition or deletion is repeated while confirming the display of the piecewise polynomial function to obtain an optimal data set.

FIG. 1 shows an example of the shape of the contact lens according to the present invention that promotes tear exchange. In FIG. 1, point sequences 30, 31, 32, 33, and 34 are part of point sequence data representing the shape of the back surface of the contact lens obtained from the data of the corneal shape and the distance between the cornea and the back surface of the contact lens. Rows 100 to 106 are dot row data representing a shape that promotes tear exchange. The shapes represented by the piecewise polynomials having these point sequence data as nodes are illustrated by curves 3 and 4, but the point sequence data 1 shown in FIG.
It can be seen that the width of the portion where the cornea and the contact lens are in contact at the minimum interval is narrower than the shape represented by the piecewise polynomial in the case where there is no 00 to 106 (only the dot sequences 30 to 34). This can be confirmed clinically by wearing a contact lens and placing the fluorescein solution between the lens and the cornea.

FIGS. 3 and 4 show fluorescein patterns of lenses having the shapes of FIGS. 1 and 2, respectively. The thickness of the tear film below the lens is reduced at the portion shown in FIG. 3A, and it can be seen that this width is smaller than the width of the same portion b in FIG. Further, the function and effect of the lens having such a shape that promotes the exchange of tears can be confirmed also by wearing the lens and measuring the tear exchange rate under the contact lens. For example, a fixed amount of a fluorescein solution is dropped on the rear surface of the lens and worn, and the fluorescein concentration under the lens is quantified with an anterior fluorometer (FL-500, manufactured by Kowa) at regular intervals, and the concentration is determined by tear exchange. Is determined, the half-life of tear exchange of the lens showing the fluorescein pattern shown in FIG.
The half-life of tear exchange in lenses that exhibit a fluorescein pattern of about 3 times.

In the piecewise polynomial of the present invention, one polynomial a0 + a1x + a2x ＾ 2 + a3x ＾ 3 is used between a node and an adjacent node, using the point sequence data obtained as described above as a node.
..., One polynomial corresponds to each of the different nodes, and nodes that are knots between polynomials have smooth properties. A spline function is known as such a piecewise polynomial function, and is used in computer graphics, CAD, and the like. There are various functions as spline functions, which can be selected according to the purpose. For the purpose of the present invention, a B-spline can be used, and an odd-order spline interpolation function and a Riesenfeld spline that can add or delete nodes are preferable. These specific examples are described in a copy of a spline function, a copy of data analysis by a computer, and the like, and are appropriately used from these.

The contact lens of the present invention sends the interpolated point sequence data based on the piecewise polynomial obtained as described above to an arithmetic processing unit of a lathe driven by numerical control, and performs cutting based on the data. To form the rear surface of the lens, and then cut the curve of the front surface of the lens by a known method. For cutting a curve on the front surface, it is also possible to generate point sequence data representing the shape, generate a piecewise polynomial from this data, and cut the curve into a shape corresponding to this. Since the contact lens of the present invention forms a smooth shape by cutting, it is possible to omit the conventionally required shaping of the joined portion of the cut surface by polishing processing, and it is possible to shorten the processing cycle. Alternatively, it is easy to manage the lens design to a constant level, and high-quality lenses can be mass-produced industrially. In addition, since a lens that matches the shape of the cornea of the lens wearer can be produced, it is possible to supply a lens that is excellent in wearing feeling and that has improved eye safety.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) A corneal shape analyzer SK2000 for corneal shape analysis
(Manufactured by Sun Contact Lens Co., Ltd.) to obtain point sequence data representing the corneal shape by spherical approximation at 0.5 mm intervals from the center of the cornea. The point sequence data (data 1) representing the shape of was obtained. On the other hand, from the prescription example of the contact lens, the rear surface of the contact lens having the desired lens movement, tear exchange rate and feeling of wearing is analyzed by a bevel analyzer and a shape measuring instrument, and the junction between the optical part on the rear surface of the contact lens and the peripheral part is analyzed. The shape of (the part that promotes tear exchange) was obtained as point sequence data (data 2) at intervals of 0.1 mm. This data was combined with the above-mentioned point sequence data of the rear surface shape of the contact lens, and the point sequence data was integrated such that a site for promoting tear exchange was located 3.7 mm from the center of the lens. Based on this point sequence data, an interpolated curve was obtained by a computer using a curve generation program based on an odd-order spline interpolation function (described in "Spline Function by Personal Computer", published by Tokyo Denki University Press) (Data 3: Coefficient matrix of spline function values).

Further, interpolation data for dividing the interval between nodes by 10 using the interpolation function was obtained. Next, this interpolation data is
It was sent to a C-controlled automatic lathe and the back surface of the contact lens was cut. After polishing the cutting surface, it is bonded to a processing jig and the front part of the lens is cut into a predetermined shape.After polishing the cutting surface, the lens is peeled off from the processing jig and the lens end is finished. Polishing gave a hard contact lens having a diameter of 8.8 mm. FIG. 3 shows a schematic diagram of a fluorescein pattern when this lens is worn. The half-life of tear exchange measured by Kowa's Anteria Fluorometer FL-500 was about 2
Minutes.

Data 1 (lens size 8.8 mm) (0, 0), (0.5, 0.016), (1.0, 0.
065), (1.5, 0.147), (2.0, 0.2
64), (2.5, 0.417), (3.0, 0.60)
8), (3.5, 0.836), (4.0, 0.87)
7), (4.4, 0.538) Data 2 (3.3, 0.7430), (3.4, 0.791)
0), (3.6, 0.8834), (3.7, 0.91
14), (3.8, 0.9083), (3.9, 0.9
021), (4.1, 0.8088), (4.2, 0.
7231), (4.3, 0.6237)

Data 3 (coefficient matrix composed of spline function values) 1.0 0 0 0 0 0 0 0 0 0 0.25 0.55 0.2 0 0 0 0 0 0 0 0.06667 0.6 0.33333 0 0 0 0 0 0 0 0.125 0.69269 0.19231 0 0 0 0 0 0 0 0.08654 0.56624 0.34722 0 0 0 0 0 0 0 0.02778 0.52222 0.45 0 0 0 0 0 0 0 0.09999 0.73333 0.16667 0 0 0 0 0 0 0 0.16667 0.66667 0 0 0 0 0 0 0 0 0.16667 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.125 0.59375 0.25625 0.025 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.16667 0 0 0 0 0 0 0 0 0.66667 0.16667 0 0 0 0 0 0 0 0.16667 0.66667 0.16667 0 0 0 0 0 0 0 0.16667 0.66667 0.16667 0 0 0 0 0 0 0 0.16667 0.66667 0.16667 0 0 0 0 0 0 0 0.16667 0.66667 0.16667 0 0 0 0 0 0 0 0.16667 0.70833 0.12500 0 0 0 0 0 0 0 0.33333 0.55556 0.11111 0 0 0 0 0 0 0 0 0 1.000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.04167 0.31944 0.51389 0.125

(Comparative Example 1) In Example 1, point sequence data (data) representing the rear surface shape of a contact lens represented by point sequence data obtained by adding a desired interval between the cornea and the contact lens to the point sequence data of the cornea shape. 1) Based on the above, the contact lens processing data is generated by using a program of an odd-order spline interpolation function.
A contact lens was manufactured in the same manner as described above. FIG. 4 is a schematic view of a fluorescein pattern when the obtained lens is worn.
It was shown to. The movement of the lens was slow, tended to meander instead of sliding down smoothly from the upper part of the eye to the lower part, and as a result of measuring the tear exchange rate, the half-life was 7 minutes. It was three times.

[0021]

According to the contact lens of the present invention, since a smooth shape is formed by cutting, it is possible to omit the conventional shaping of the joint of the cut surface by polishing, which is essential, and the processing cycle can be shortened. Not only is possible, it is easy to manage the lens design consistently, and high-quality lenses can be mass-produced industrially. In addition, since it is possible to create a lens that matches the shape of the cornea of the lens wearer, the lens is excellent in wearing feeling, and the shape of the part that promotes tear exchange is constant and the eye safety is further improved It is possible to supply

[Brief description of the drawings]

FIG. 1 is an enlarged view of a peripheral portion of a contact lens of the present invention.

FIG. 2 is an enlarged view of a peripheral portion of a contact lens having a design that does not include a dot sequence representing a shape of a part that promotes tear exchange.

FIG. 3 is a fluorescein pattern when the contact lens of the present invention is worn.

FIG. 4 is a fluorescein pattern when the contact lens having the design of FIG. 2 is worn.

FIG. 5 is a diagram showing an outline of the contact lens of the present invention.

FIG. 6 is a flowchart showing a flow of designing and manufacturing the contact lens of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cornea 2 Contact lens 3 Contact lens posterior optical part curve 4 Contact lens posterior peripheral part curve 5 Contact lens posterior optical part 6 Site which promotes tear exchange 7 Contact lens posterior peripheral part 30-34 Cornea shape point Point sequence data representing the shape of the contact lens posterior surface obtained from the column data and the desired distance data between the cornea and the contact lens posterior surface (partial) 100-106 Point sequence data representing the shape of the site promoting tear exchange

Claims (6)

[Claims] 1. A contact lens having a surface conforming to the shape of the cornea and having a curved surface shaped to promote lacrimal fluid exchange, the data representing the shape of the cornea and the distance between the cornea and the posterior surface of the contact lens. From the point sequence data representing the shape of the back surface of the contact lens obtained from the data representing the lens, and the point sequence data representing the shape promoting the tear exchange, a polynomial that approximates the lens shape in the adjacent section joined at these data points A contact lens that generates a piecewise polynomial with the first derivative equal at its data location and has a posterior surface corresponding to the plurality of piecewise polynomials. 2. The contact lens according to claim 1, wherein the piecewise polynomial is a spline function. 3. The contact lens according to claim 1, wherein the piecewise polynomial is a B-spline function. 4. The central optical part of the contact lens is a spherical surface substantially conforming to the shape of the cornea, a curved surface for promoting tear exchange is connected to the outside, and a curved surface substantially conforming to the shape of the cornea is connected to the outside. A contact lens in which a curved surface from an outer peripheral portion of the central optical portion to a peripheral edge portion of the lens has a curved surface corresponding to a piecewise polynomial. 5. A central optical part of the contact lens is a spherical surface substantially conforming to the shape of the cornea, a curved surface for promoting tear exchange is connected to the outside thereof, and a spherical surface substantially conforming to the shape of the cornea is connected to the outside thereof. A contact lens having a curved surface that promotes tear exchange and has a curved surface corresponding to a piecewise polynomial. 6. A method according to claim 1, wherein data representing the shape is stored, a segmented polynomial is generated based on the data, and the surface of the contact lens is cut based on the polynomial.
A method for producing the contact lens according to the above.