Continuously variable contact lens

Docket No. P-83155-32

Continuously variable contact lens so

BENJAMIM ÍTTJCHMAN, and SANG Y.WIIANG, intend to obtain the privilege of invention in Portugal.

Soft, continuously variable multifocal contact lens where there is a continuous optical gradient in a region smaller than the maximum pupil aperture. The concave surface is aspherical with a desired optical power for distance viewing in the center and increasing to the desired power of near vision. The magnification is usually about 3 to 5 diopters within 6 mm of the anterior optical zone (AOZ) which is approximately 9.7 Tim in diameter when moist. From this 6 mm zone the concave surface is essentially spherical. The concave surface is an aspheric curve having a steeper curve in the middle of the base curve than the base curve.

Once determined the curves r? The thickness of the lens (t) and the radius of curvature for AOZ designated r1 is calculated using the maximum optical power of the lens (IT) and the desired thickness at the AOZ junction (JTK) based on P * - ...............

'.ni * equation.

ri x Exp tx Exp n-1 n where Exp is the coefficient of dilatation <lens when wet, are all dry ores before dilation »lm, around, and half-way no index. refraction of the mold-related diameters manufactured by the compression method or may be duplicated

KJ pi moJrk cif / '?? ... G

Λ r

s.

x.

í _f-

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Docket No. P-83155-52

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-2 DESCRIPTION

This invention relates to contact lenses and, more particularly, continuously varying multi-contact lenses suitable for creating sharp images of distant objects, in-term objects and near objects simultaneously on the retina. including lenses designed to correct astigmatism.

There is great demand and interest in correcting a contact lens that can be used successfully for both viewing distances as well as for close reading. There are currently three guidelines for trying to solve this problem. These orientations include the alternating bifocal vision contact lens and the simultaneous bifocal vision lens which encompass both the right eye / left eye method and the combined bifocal lens.

The bifocal alternating vision contact lens generally has two optical zones. The first optical zone for viewing distant objects is usually in the middle of the lens. The optical zone for viewing close objects generally surrounds the first optical zone. Each optical zone is larger than the nasal opening of the pupil so that the user has to adapt the lens position accordingly to the desired application, it is a difficult task to train the patient to move to two optical zones when desired. This is especially true with the large, comfortable, soft, freely moving contact lenses to change the position of the optical zones at will. Thus, these lenses are not completely satisfactory, and often the transition between the two Optical zones is placed in front of the pupil resulting in a confused view.

Simultaneous bifocal vision contact lenses have advantages over the ability of the human brain, which has the ability to choose relatively sharp images when there are two clearly confused images projected simultaneously onto the retina. This ability to choose the sharp image leads to two orientations using this method. In the left eye / right eye method, one eye is equipped with a distance vision lens and the other eye is equipped with a near vision lens. The brain selects vision in one eye at a time. obviously, as one eye is used at a time, the user loses the sense of depth.

The second orientation, which uses hyphenal contact lenses

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Doeket No. P-83155-32

For simultaneous vision, the bifocal mixed lens with an optical zone smaller than the pupil aperture. This is similar to the alternate view described above, which has two optical zones. The distance zone in the center of the lens is made smaller than the normal pupil aperture to ensure that both optical zones are presented simultaneously on the pupil. The transition between the two optical zones is graded in an attempt to reduce the abrupt discontinuity and glare caused by rapid transition between zones. Assuming the transition is gradual, continuity between the two viewing zones cannot be continued. Significantly, for any object between the near and far zones, two equally blurred images will be formed on the retina 0 which will cause confusion to the user.

Based on the foregoing, it can be seen that all three ways to obtain multifocal contact lenses currently under study present several problems that are inherent in any bifocal lens. Because lenses have two optical zones, one for reading and one for remote viewing, there are many intermediate things, such as the dashboard of a car, that are blurred or have equally blurred double images. Another drawback of each of the guidelines under study, when applied to more comfortable malleable lenses, is that astigmatism is difficult to correct. Accordingly, it is desirable to create continuously variable, multifocal contact lenses which eliminate the drawbacks of prior art lenses.

SUMMARY OF THE INVENTION

Generally and according to the invention, an improved contact lens with a continuously varying multifooal optical power gradient is established having a diameter that is smaller than the normal pupil aperture in the middle of the lens. of contact. The desired distance vision power is in the central region of the lens, increasing the power to the desired near vision value in a pupil aperture diameter orientation of about 5 to 7 mm to be able to create sharp images of distant objects, intermediate objects, and near objects simultaneously on the user's retina. zador.

In the non-toric lens, the lens has a complete rotational symmetry. · In a typical eye-view lens the largest negative power of -3 to 5 diopters in the center grows to zero to a diameter of

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Docket No. P-85155-52 at 7 mm θ is maintained at zero diopter to the extreme optical zone up to approximately 9.7 mm in diameter. The concave surface of the aspherical lens and the other surfaces may be spherical, aspherical or therae.

Soft lenses are generally prepared in the rigid state prior to expansion, so that all calculations are performed using the dry (or rigid) dimensions except the calculation of the optical power. Epic powers for swellable lenses are calculated in the wet (or pliable) state using the dry-state dimensions multiplied by the appropriate dilation or expansion coefficient.

P_w «_1_ - n-1_ rl x Exp tx Exp r2 * x Exp n-1 n where:

Exp is 0 coefficient of expansion n is 0 refractive index of material when wet t lens thickness r2 * is 0 radius of curvature of concave surface, in center rl is radius of curvature of convex surface

The lenses according to the invention are prepared by compressing a pellet (hotSo) of material by a ball by cutting the pasty. material while being held by compression and then releasing the tablet after cutting and polishing. The polished β cut surface prior to release is spherical and after release is spherical. The value of the strain created by compression is measured by means of a micrometer indicating the value of the displacement. A detailed process is described in our US Patent⁵ 4.074.469.

The aspheric concave surface generated by this process is essentially spherical with a diameter of 5 mm (prior to expansion) and has a radius of curvature of base R r. The aspheric curve has a radius greater than the base curvature in the middle. The radius of curvature of this curve is farthest in the center and is designated by The difference between r2 * β

Γ2, as well as the clearance distance between the authentic curve and the spherical curve, and the magnitude of the gradient diameter are controlled by the value of the compression, the diameter of the compression ball, and the depth of cut (or remaining thickness of the cut material). Once determined r2 θ^r2*’ ^The lens thickness t and radius of convex curve rl are calculated using the desired optical power

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Dooket No. P-83155-52 «»

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at the lens axis and the desired thickness at the junction of the optical zone. The respective lens parameters are designed using conventional methods.

As long as the lens has a rotational symmetry the equi potential contour will be a circle. For an astigmatised eye an oliptic contour will create a clear image of the object on the retina as long as the required vertical optical power and horizontal optical power are available in the lens within the normal pupil aperture, namely within a region 5 in diameter, before lens dilation.

It is therefore one of the objects of the invention to establish an improved contact lens.

Another object of the invention is to establish a continuously variable multifocal contact lens.

It is yet another object of the invention to provide a continuously variable multifocal contact lens wherein the concave surface is asphaltic.

It is a further object of the invention to establish a multifocal contact lens having a continuously variable optical zone in the middle of the lens with a diameter smaller than the normal pupil aperture.

Still another object of the invention is to establish a method for forming a continuously variable multifocal contact lens.

A further object is to establish an improved, continuously variable, multifocal contact lens for correcting astigmatism.

Still other objects and advantages will be partly apparent and partly apparent from the specification.

Accordingly, the invention comprises the various steps and the connection of one or more of these steps with respect to each other, the resulting article having the characteristics, properties and relationships of elements which are exemplified in the following detailed description. The scope of the invention is indicated in the claims.

BBEVE DESCRIPTION OF DRAWINGS

For a complete understanding of the invention, reference is made to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a plan view illustrating the optical pot gradient of a malleable contact lens constructed and arranged in accordance with the invention;

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Socket No. P-8J155-32

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PIG 2 is a cross-sectional view of the PIG soft contact lens. 1 before dilation;

SIG, $ and 3a are sectional views of the lens preparation process of SIG.le 2;

PIG 4 is a cross-sectional view of a portion of the PIG lens.

2. showing the relationships of dimensions for lens construction.

PIG 5 is a partial cross-sectional view of the peripheral region of the side of PIG.le 2;

PIG 6 is a plan view of the lens of PIG1 showing circular shaped bands of the optical zone used for distance vision and near vision in the lenses of FIGS. 1 and 2; and

PIG 7 is a plan view of the PIG lens. 6 showing a band for distance vision with astigmatism correction.

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DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a top plan view showing a continuously varying multifocal contact lens in the wet state or conditions of use when prepared in accordance with the invention. The lens has a complete rotational symmetry with the highest negative power of approximately 4 diopters in the center and increasing to 0 diopters within a zone having an approximate diameter of 6 mm. The lens is lenticular having an anterior optical zone of approximately 9.7 mm in diameter. 0 total expanded lens diameter is approximately 14.7 mm.

The lens of PIG.1 may be formed of any commercially available contact lens material. For example, specific lenses made according to the invention described herein are formed of HEMA material, such as hydroxyethyl methacrylate. The invention is also applicable to all lens materials analogous to HEMA, ethylene glycol dimethalylate (EGMA) or analogs thereof, polymethacrylate (PMMA) or analogs thereof, polyvinyl pyrrolidone (PVP) and the like. Generally, these soft lens materials increase and absorb varying amounts of water depending on the specific polymer material. Generally available HEMA lens materials increase with a water content of 55% 45% or 3θ%.

Referring now to PIG. 2, a cross-sectional view of the lens shown in FIG. 1 in its dry state is shown prior to expansion. All dimensions in PIG. 2 are reduced by 17% from PIG.l. This is due to the fact that the design and manufacture of malleable lenses

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Doeket No. P-83155-32 according to the invention are established in the dry state prior to dilation. Accordingly, the following descriptions are set using the dry state dimensions, except for the calculation of the optical power. The optical power is calculated for the wet state using the dimensions in the dry state, multiplied by the appropriate dilation factor. For the HW material used in the exemplary configurations, the expansion factor is 1.21 and the dilated lens contains about 45% water. The coefficient of expansion for a lens material containing 35% water is 1.18 and for 55% water is 1.31.

In the lens illustrated on the PIG. 2, all curves are spherical except the inner concave eurva which is aspheric. This base curve is essentially spherical about 5 mm in diameter and where the base curve has a radius r2 · If the inner concave curve were spherical with the same radius rg the inner concave curve would follow the curved line indicated in the dotted line. middle of the lens. As can be seen from SGA 2, the curve is deeper in the middle than the base curve rg · The radius of curvature of this aspheric curve is larger in the center and is called rg *. Controlling the difference between r2 * β rg, as well as the displacement distance between the authentic curve (solid curve line) and the spherical curve (dashed line), as well as how to produce the gradient within the intended diameter, represent important aspects. of the invention. The concave surface of the lens is aspheric and the other surfaces may be aspheric, spherical or thermal. From the central epic region, the concave surface of the lens is essentially spherical.

Once the dimensions of the curves rg 'and rg are determined, the thickness of the lens (t) and the convex curve with the radius of curvature r1 are calculated using the desired maximum optical power of the lens and the desired thickness. at the junction of the anterior optical zone (AOZ) which has been nominally set at 8 mm. The other curves are determined by the conventional methods. The bevel cut width and bevel diameter are arbitrarily selected based on experience. In the exemplary configurations the bevel width is 0.85 mm and the bevel radius is 10.3 mm. Since curve rg is essentially spherical at the junction point at 8 mm, the curvature of the peripheral convex curve having a radius, r_CXp, based on the established thickness of the joint and the desired thickness at the rim of the lens. In order to achieve the desired lens properties, namely a contact lens, simultaneously multifooal, the optical power gradient of the desired distance viewing power in the

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Docket No. P-83155-32 -gjl “θ * H lens center, should increase about 3 to 5 diopters within a region that has a smaller diameter than the normal pupil aperture. The normal opening of a pupil is the maximum opening in darkness and is generally about 6 mm in diameter. Accordingly, the optical power gradient is set in a region of the lens between about 4.5 mm and 5.5 or diameter in the dry state.

The simultaneous multifocal contact lens provides gradually varying focal power within a central region smaller than the normal pupil aperture of the wearer. Because of this, at least one part of the lens in the central region forms a clear image of the distant object on the retina while another part of the lens forms a clear image of a nearby object on the retina. Although the central region of the lens forms a confusing image of a nearby object while there is a sharp image of the nearby object on the retina, the human brain automatically selects the sharpest image of the desired object, the quality of the human brain. It is important to relate a sharp image that makes it possible for the lenses prepared in accordance with the invention to establish the continuously varying multifocal effect.

Malleable contact lenses with a concave surface including an aspherical curve providing the optical power gradient within the pupil aperture may be prepared by the apparatus and method described in our previous US Patent No.^and No. 4,074,449 recorded February 21, 197θ · θ the apparatus described therein forms the shapes of the asphoric surfaces in an optical lens by deforming the lens material in a determined manner and forming a spherical surface on the deformed lens tablet. The deformed lens material pellet is released and the concave surface formed becomes aspheric. Accordingly, the entire specification of our original patent is incorporated by reference as if set forth herein.

According to our method, a sample of uncut lens material is compressed by a ball of radius R. The tablet is then cut and polished while held in the compressed position and then released. The offset value created by compression is measured by a micrometer to show exactly which offset is made. 0 The displacement value is exactly the same as the distance between the solid aspherical line and the dotted spherical line in FIG. 2.

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Locket No. P-83155-32 «9The greater deformation of lens material prior to cutting gives rise to the largest gradient of epic potential in the end lens. Sometimes a dry sample of lens material can be so brittle that it comes off before reaching the compression value. In this case it is advisable to pre-fill the sample to avoid fracture. There is no need to polish this cut and the value of the displacement caused by compression is also measured with a micrometer.

FIG. 3 shows the relative position of ball 11 with a radius R and an uncut sample of slurry material 12 that will be bent as ball 11 is moved in the direction of the arrow. The micrometer 13 placed above the lens material 12 is used to determine the deformation applied to the lens material 12, FIG. 3 shows the position of the ball 11 the lens material insert 14, cut but not polished and the micrometer 13. Construction details of convenient equipment for holding lens materials 12 and 14 and micrometer 13 are given in detail in our previous patent. In this way, no construction details will be given here.

It is found that for a given value of central displacement (at pressure) the final thickness of the cut insert and the size of the compression ball radius R change the size of the lens region in which the optical power gradient exists. A smaller R radius of the ball produces narrower regions for asphalt zones and a larger R radius of ball 11 produces wider regions for asphalt zones. The thinnest end lens thickness for the narrowest region of the aspheric zone and the thinnest end lens thickness for the widest region of the aspheric zone. Similarly, for the same compression value, a smaller aspheric region results in a larger optical potential gradient or a deeper aspheric curve for the same opposite base curve r2. 0 is true,

The following configuration, as an example, is combi. compression and cutting which results in slowness with the following results:

Typical combination:

Ball radius used for compression R »6 mm

Eompression value Q - 25 miorons

Final thickness of cut and solid tablet Tb «1,8 mm

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Docket No. P-83155-32

Typical results:

Aspheric Zone Region Difference between r2 θ r2 * (r2-r2 *) Optical power gradient (after wet)

GOZ «5.0 mm, Δr2« 0.6 mm

A Pw = »4 diopters

The above values ​​are typical average values ​​according to the invention and are given by way of example only. They are not presented as limit values. These results obey the following relations:

GOZ - f (Q + Tb + R)

T2 - g (Q-Tb-R)

Pw - h (Q-Tb-R)

That is, an increase of Q increases GOZ, / ^ r2 and ^ Pw while an increase of Tb or R increases GOZ, but decreases / ^ r2 and ^ Pw.

<td>Once compressed the tablet</td><td>material, cut and polished on</td>

<td colspan="2">cava surfaces (central base curve and bevel curve) the insert is</td>

<td colspan="2">released and measures are taken. The following information is obtained from</td>

<td>tablet.</td><td></td>

<td>1. Compression value</td><td>Q</td>

<td>2. Peripheral Base Curve</td><td>r2</td>

<td>3. Center Curve</td><td>r2 '</td>

<td>4, Thickness of cut insert</td><td>Also</td>

<td>5 · Bevel radius</td><td>r3 (normally fixed)</td>

<td>6. OZ Perimeter</td><td>POZ (usually fixed)</td>

<td colspan="2">In order to complete the lens design,</td>

<td>or known the following elements:</td><td></td>

<td>7. Lens power at center</td><td></td>

<td>(when wet)</td><td>Pw</td>

<td>8. Total lens diameter</td><td>DL</td>

<td>9. Anterior epic zone (OZ)</td><td>AOZ</td>

<td>10, AOZ joint thickness</td><td>JTK</td>

<td>11.Thickness of edge</td><td>ETK</td>

<td>12.Refraction index (when wet)</td><td>no</td>

<td>13.Expansion Factor</td><td>Exp</td>

The remaining unknown parameters to calculate are:

The)

b) o) d)

The lens thickness t

AOZ radius of curvature rl

Rl angle for a given AOZ; ° 1

Radius of curvature of the convex zone rexp

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In this numerical example many non-variable parameters are assumed and typical values ​​are given for practical reasons:

1) Q - 0.025 mm

2) r2- variable

3) r2 * = »variable

4) Tba 1.8 mm

5) ≤ 10.3 mm

6) P0Z = 10.45 mm

7) Pw 'variable

8) DL-12.15 mm

9) AOZ-8 mm

10) JTK-O7 mm

11) ETK-0.06 mm

12) n-1.4325

13) Exp-1.21

Using the numeric values ​​you can type the following equations:

Pw - 1 - n-1 rl x Exp - tx Exp r2 'x Exp n-1 n

(l) to 13) above, perl, r2 in meters

Pw -_1__ rl x 1.21 - tx 1.21 r2 * xl, 21

0.4325 1.4325 for r 1 and r2 * in millimeters p »“ ______________ 1_- PPL · (1) rl t r2 *

357 ” 1184

Regrouping Equation l) otherwise:

rl -t - 1

357 1184 Pw + 557 r2 »rl - 0.3O19t + 1_

Mp + 1 357 r 2 · r 1 ~ 0.319t-¼ Cp (2)

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-12 'where

Cp-1

Pw + _1_

357 r2 «(3)

Note rl and r2^r in equations (l) (2) and (3) are expressed in millimeters_O

Making the JTK junction thickness -0.07 mm, from _1 ^ 2 + 3-4 = 5 r2 - \ fr2²-16 + 0.025 + t - (r_x- \ fri²-16) «0.07

Figure 4 we have

Cos 0₂ and ®2 “ ^sen “* 4— r2 solving with respect to t, we have t-rl- ¥ rl -16 r2- \ fr2 ^ -16 + 0.025- 0.07 cosfsen¹ 4 j r2 t «* rl - ^ r] / - 16 - K where K« r₂ - \ [r₂² - 16 + 0.025 - 0.07 os¹4 ) r2 (4) (5) (6) being₂ in millimeters ·

Solving with respect to equations (2) and (5) 1 t = 0.310t + Cp - 4 (° »3019t * Cp)²-16 - K (7) by the substitution of ri of equation (2) in equation (5) Solving with respect to t of equation (7) we have 1 t »2,524Cp -1,762K - 6.3706 Cp²-3,847kCp + 0.58K2 - &lt;0.58 (8) of which 1

K r2 - \ fr2² -16 + 0.025 - 0.07 cos (sin r2 ^}

Cp »_1

Pw + 1

357 r2 »(6) (3)

For a given set of values ​​of r2, r2 * and Pw, Cp and K can be calculated and t can be calculated using Cp and K. Then rl β Θ1 are calculated.

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Pocket No. P-83155-32

-13Example t

6.44 Pw = —3

6,808

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For r2 '6.94 r2' *

Cp * _1_ ³ _ςΣ_ +

357 6,44

K 6.94 - J 6.94²-16 + 0.025

- 0.07 = 1.2080 cos (sen “^,14 )

6.94 t - 2.524 x 6.808 - 1.762 x 1.2080 - | 6.3706 x 6.808 ^ -3.847 x 1.2080 + 0.58x 1.2080²-40_;38 »0.085 rl« 6.808 ♦ 0.3019 x 0.085 = 6.83 = »sen 4 (9) rl« sen **¹ 4 “ 35,62 6,85

In calculating thickness t it is preferable to keep the joint thickness equal to 0.07 mm, for example. However, for much lower lens power values, the calculation may give lenses with very thin or negative thicknesses. For proper design, a minimum thickness is maintained, preferably about 0.04 mm, for example. In such cases, the joint thickness could be set at a value greater than 0.07 milli meters.

Knowing r2 and r3, POZ, DL AOZ and ETK and calculating the thickness at the JTK junction (0.07 mm or greater) the anterior peripheral curve r_CXp may be calculated in the conventional manner. For example, when r₂=&gt; 6,94 mm, rj = '10,3 mm, POZ =' 10, 45 mm, DL = '12,15 mm, ETK = 0, 0 mm, the value of JTK may be 0,07 mm in the as the curve rl is smaller than 7.03 mm. This gives for^rcxp the value of 8.13 mm. For rj greater than 0.07 mm the JTK value increases_CXp decreases.

following is an example calculation for r_CXp, with reference to FIG. 5

dl + d2 + d3 -d4 dl d2 d3 r3² - 2,225² - ψ r3² - 6,075² r₂² - 4² - (r₂² - 5»225²

0.07 to t ^ 0.04 mm

0.558 5 cos (sen '“¹ 4 j 12 (10)

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Docket No. P-83155-32

-14 ~ ^d3

0.07 cos (sen Λχ) + 0.04 - t ^r2 to t = 0.04 mm (ll)

Λ * · 'is the calculated thickness of the lens according to equation (8) ^d4 = "0.06- 0.0743 oos (sin 6.075) 10.3 whence:

T - 0.5586 * (r₂²-4² - J r2² - 5,225²) + d? - 0.0743 (12)

To rg⁵»¹ 6.94 mm, r2 * “6.44 mm and Pw = -3 used in the example above, the thickness is 0.085 mm which is greater than the minimum practical value of 0.04 mm. So:

Y - 0.484 + (Jr₂²-4² - \ fr₂²-5,225²) + d3 - 0.484 + 1.1037 + 0.0857 - 1.6734 ^Yl ~ ......, 4^X? ,, P7 ^ „y _and 3,2866 (13)

Y2 - 6.015x2x015, _7&gt;5529y

5.4098 jTyl ± y2)² \ 6,075²

2_ \| 5,4098² + 6,075² - θ, 13 mm exp • exp (14) (15) (16) (17)

If te greater than 0.04 mm, r_exp is always greater than 8,13 If, for example, the calculated t is t '· -0,01 mm: d₅ - 0,0857 + 0,04 - (-0,01) »0,1357 which will be the true JTK to make the center thickness 0,04 mm.Nes, te eso:

Y - 0.484 * 1.1037 + 0.1357 »1.7234 ^γ1-4 x 2,075 - 1.7234 - 3.0927

1,7254 ^γ2 = 6.057 x 2.075 _and 7,3144

1.7234 ta * *?).

5.2035 mm λ *.

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<img file="PT78469B_D0014.tif" />

<img file="PT78469B_D0015.tif" />

Equations (3), (6), (8), (2), (9), (10), (11), (10), (14), (15), (16) and (17) can be solved by hand or programmed on a calculator or computer for paper printing from:

t, χχ, © χ ex_CXp P^{for 11111} given set of r₂, x2 * and Pw.

The examples given above give details of the design and manufacture of simultaneous multifocal soft contact lenses which I use. use the compression, cutting and polishing methods. Once the lens is made in this manner, the lens can be easily duplicated by casting or molding. Another alternative method may be to copy the spherical tablets by casting or molding means and cut the front portion according to the patient's needs. For the purpose of making a mold or die, a suitable metal may be used instead of the lens material to make the reliefs according to the invention.

The same technique can be applied to rigid contact lenses. However, the variable focal length effect is strongly reduced in a rigid contact lens because the liquid space formed between the cornea portion and the posterior aspherical surface functions as a reducer of the optical power gradient. The cornea is aspheric but tends to be spherical in the center and strongly flattened at the extremes. This is quite the opposite of the aspheric surface of the lens created by the pressure drop method. The soft lenses, however, adapt to the surface of the cornea so that the space with tear fluid is negligible. This means that when using soft lenses the posterior lens surface becomes spherical (if the cornea is spherical), becoming the aspheric anterior surface and maintaining the same variable focal length for which the lens was designed.

FIG. 6 shows a circular matte band in the middle of the lens that can represent the band used for distance viewing. This band has an optical power of about -3 diopters. The outer band can be used for close view and has a power of -0.5 diopters.

FIG. 7 shows the same lens as FIG. 6 wherein there is an elliptical band in the optical zone of the lens which can be used for distance vision in astigmatism correction.

example shown in FIG. 7 is for an eye with -2.5 diopter on the vertical meridian and -3.5 diopter on the horizontal meridian. As soon as the lens is analytical (continuous smooth variation) and the power gradient region is within 6mm of the pupil aperture diameter,

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-The lens has the property of simultaneous multifocal vision, with possibility of correcting astigmatism. In the case of greater astigmatism (greater than the lens power range can correct), the anterior surface can be made toric by conventional means used for astigmatism correction on any contact lens for monovision. In a multifocal toric lens, the equipotential contour may not be of concentric circles as shown in FIG. 1, but will be of concentric ellipses.

Therefore, by establishing a malleable contact lens wherein the aspheric properties are concentrated in the central portion of the lens, in a region typically smaller than the normal pupil aperture, a lens having simultaneously multifocal properties is obtained. By establishing the desired distance vision power in the central region and increasing optical power in an asphoric region having a gradually varying power within the normal pupil aperture, a portion of the lens near the central portion will form a sharp image of a distant object over the the retina and another part of the lens in the peripheral zone will form a clear image of nearby objects. Although the central region of the lens forms a blurred image of nearby objects as soon as there is a sharp image of the object on the retina at the same time, the human brain selectively chooses the sharp image of the desired object. Intermediate vision and close vision is readily provided according to the invention. The elliptical bands within the pupil opening form a sharp image for the astigmatised eye. Continuously variable multifocal contact lenses may be prepared by deforming the lens material in a predetermined manner and forming spherical surfaces on the deformed material to form the asphoric region within the normal pupil aperture.

It will be appreciated how the above set of objectives, as evidenced by the descriptions made, have been efficiently achieved, and how certain variations can be made in carrying out the indicated process and in exposing the articles without departing from the spirit and scope of the invention, It should be understood that all the subject matter contained in this description and indicated in the accompanying drawings shall be construed as exemplary and not in the limiting sense,

It will also be understood that the claims are intended to encompass all generic and specific features of the invention described herein and all exposures of the object of the invention which may be

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Any language problems may be included with them.