WO2001051978A1

WO2001051978A1 - Ophthalmic lens

Info

Publication number: WO2001051978A1
Application number: PCT/FR2001/000006
Authority: WO
Inventors: Nicolas Chateau; Dominique Baude; Bruno Fermigier
Original assignee: Essilor International (Compagnie Generale D'optique)
Priority date: 2000-01-14
Filing date: 2001-01-02
Publication date: 2001-07-19
Also published as: FR2803922B1; FR2803922A1

Abstract

The invention concerns an ophthalmic lens such as a contact lens, whereof one of the surfaces is spherical or aspheric mechanically adapted to the shape of the eye, whereas the other simultaneously provides correction for gradual simultaneous vision presbyopia, astigmatism and optionally for myopia or spherical hypermetropia, the shape of said surface being easily determined from the shape of the first surface and the optical path which said lens should provide.

Description

"Ophthalmic lens"

The invention relates to ophthalmic lenses for correcting the vision provided by an astigmatic eye, possibly myopic or hyperopic.

We know that the correction of astigmatism is obtained thanks to a toric surface whose plane of symmetry must be oriented along a meridian plane of the eye to be corrected, that is to say along a plane containing the axis optics of this eye, the parameters usually used to define the correction to be made, on the one hand, the angular difference between the meridian plane along which the toric surface must be oriented and a reference meridian plane, corresponding to the horizontal meridian plane when the wearer of the lens is standing, this angular difference being generally called the "axis" of the correction, and, on the other hand, by the cylindrical optical power introduced, generally called "cylinder value".

When the ophthalmic lens is an intraocular implant, the toric surface remains correctly positioned relative to the eye simply because it is arranged inside the eye.

On the other hand, when the ophthalmic lens is a contact lens, provision must be made for stabilization so that the lens remains permanently correctly positioned vis-à-vis the eye, and in particular a ballast prism enabling the lens to be kept in position thanks to gravity, or bumps as described in French patent 2,760,853, which use the dynamic effect produced by the blinking of the eyelids so that the lens remains permanently correctly positioned, or even at the top and bottom of the lens, a progressive thinning or lightening along a direction which must correspond to the vertical direction of the eye, as described in American patent 4,095,878, or else a stabilization means comprising a ballast and a reduction in the upper part of the lens, as described in US patent 4,324,461. All these stabilization means, with the exception of the ballast prism, are located outside the corrective portion of the contact lens, located in the center thereof, at the level of the pupil of the eye to be corrected, for example inside the circle of radius 4 mm centered on the optical axis of the lens.

We also know that the correction of myopia or hyperopia is obtained thanks to a spherical surface whose center of curvature must be on the optical axis of the lens, the parameter usually used to define the correction to be made the spherical optical power introduced, generally called "sphere value"; and that in the presence of an eye that is both astigmatic and myopic or hyperopic, the toric surface necessary for the correction of astigmatism and the spherical surface necessary for the correction of myopia or hyperopia are combined.

We also know that the correction of presbyopia is advantageously obtained thanks to a complex surface providing a correction with progressive simultaneous vision, that is to say a correction whose power varies gently (and not suddenly) between the center and the periphery of the corrective zone, so that several images are formed simultaneously on the retina, the useful image being selected by cortical sorting. It is sometimes accepted that correction with progressive simultaneous vision also makes it possible to benefit from a correction of weak astigmatisms, the useful image being selected not according to a circle centered on the optical axis, but according to an ellipse of which the largest dimension is oriented along the axis of the required astigmatism correction.

On the other hand, when the astigmatism values to be corrected are relatively high (for example greater than 1.00 diopter in absolute value), it becomes imperative to combine both a progressive simultaneous vision correction and a toric correction, as in the US Patent 4,580,882, which describes for this purpose a contact lens in which the anterior surface of the corrective portion is toric while the posterior surface provides a correction with progressive simultaneous vision. The invention aims to facilitate the manufacture of an ophthalmic lens capable of correcting astigmatism, in the case where this lens must also correct presbyopia and possibly spherical ametropia, i.e. myopia or hyperopia.

To this end, it proposes an ophthalmic lens comprising a corrective portion for correcting the vision provided by an astigmatic eye, possibly myopic or hyperopic, provided so that a reference meridian of said lens remains aligned with a predetermined meridian of said eye; characterized in that said lens also corrects presbyopia and in that said corrective portion has an anterior surface and a posterior surface one of which, called the first surface, is spherical or aspherical mechanically adapted to the geometry of said eye and the other of which , called the second surface, has a complex shape offering both a correction of presbyopia with progressive simultaneous vision, a correction of astigmatism and possibly a correction of myopia or spherical hyperopia, so that the combination of the first surface and the second surface introduces a varying optical path, as a function of the distance from the optical axis and as a function of the angular deviation from said reference meridian, at least when this distance is between 0.4 mm and 2 , 4 mm, in a distribution falling within an area between a lower envelope surface and an envelope surface s higher, corresponding respectively to the following equations: δ _ιnf (h, θ) = δ ₀ + δ _s (h) + δ _p (h) + δ _A (h, θ) - 0.9 h ² δ _sup (h, θ ) = δ, _nf (h, θ) + 0.18 h ² equations in which:

- δ, _nf (h, θ) and δ _sup (h, θ) are expressed in micrometres (μm);

- h is the distance from the optical axis, expressed in millimeters (mm);

- θ is the angular deviation from said reference meridian, expressed in radian (rad);

- δo is an arbitrary constant; - δ _s (h) is, in the event of spherical correction, the optical path provided for this correction, varying as a function of the distance h relative to the optical axis;

- δ _p (h) is the optical path, varying as a function of the distance h from the optical axis, provided for correction with progressive simultaneous vision; and

- δ _A (h, θ) is the optical path provided for toric correction.

It goes without saying that the terms "optical path" used above, and more generally in the present specification, more precisely designate the difference in optical path introduced by the lens on the rays coming from a light point located at infinity on the optical axis, so that the phase shift φ introduced by the lens is connected to the optical path δ, in the sense of the present specification, by the relation:

2πδ φ = λ where λ is the wavelength of the light ray, the negative values of δ and φ corresponding to a delay introduced on the optical wave and the positive values to an advance.

In practice, φ (h, θ) can be determined by interferometry or by another method of measuring optical phase shift. Of course, this optical path is valid for the wavelengths located in visible light, and in particular for the reference wavelength

550.10 ^"9 m.

It will be observed that the combination, on the second surface, of all the complex forms allowing both the correction with progressive simultaneous vision to compensate for presbyopia, the toric correction to compensate for astigmatism and possibly the spherical correction to compensate for myopia or l 'hyperopia, offers the advantage of facilitating the manufacture of the lens, the difficulties associated with the manufacture of a complex surface only arise for the second surface. It will also be observed that the determination of the geometry of this second surface does not pose any particular problem if the notion of optical path introduced by the lens is used, insofar as the other surface delimiting the corrective portion of the lens , that is to say the first surface, has a known shape, in this case spherical or another shape adapted mechanically to the geometry of the eye, for example, in the case where the ophthalmic lens is a contact lens. contact and that the first surface is the posterior face of the lens coming against the cornea, a shape chosen from a series of predetermined shapes, in order to provide the wearer of the lens with optimum comfort.

According to preferred characteristics, the term Ô _A (h, θ) corresponds to the equation:

δ _A (h, θ) = h ² sin ² (θ- φ)

equation in which: - C is the cylinder power required to correct the astigmatism of said eye, expressed in diopters (D); and

- φ is the angular deviation, relative to said reference meridian, of the axis required to correct the astigmatism of said eye.

In a first preferred embodiment, the lens constitutes an intraocular implant with, preferably, for reasons of simplicity, the first surface which is spherical.

In a second preferred embodiment, the lens constitutes a contact lens.

According to preferred features of this embodiment, the first surface is part of the rear face of the contact lens while said second surface is part of its front face.

Thus, it is the anterior surface of the lens that combines all the complex shapes.

Preferably, in this case, said first surface is spherical or aspherical adapted mechanically to the geometry of the cornea of said eye. This mechanical adjustment, which makes it possible to provide optimal comfort to the wearer of the lens, can be carried out very freely, since it is the anterior surface which combines the complex shapes.

The invention also relates, in a second aspect, to a method of preparing an ophthalmic lens as set out above, characterized in that it comprises: a) a step of determining the optical path to be introduced by the corrective portion of this lens; b) a step of selecting the shape of the posterior surface of said corrective portion, from a series of predetermined shapes, in order to provide the wearer of the lens with optimum comfort; c) a step of determining the shape of the anterior surface of said corrective portion, from said shape selected for the surface posterior to step b) and the optical path determined in step a); and d) a step of manufacturing said lens with said corrective portion which has the anterior surface and the posterior surface thus determined.

The description of the invention will now be continued with the description of an exemplary embodiment, given below by way of illustration and not limitation, with reference to the appended drawings. On these:

- Figure 1 is a sectional view of the lens according to the invention, along its vertical meridian plane;

- Figure 2 is a plan view of this lens; and

FIG. 3 is a partial plan view of this lens, which shows the center thereof, in enlargement with respect to FIG. 2.

The contact lens 1 illustrated in the drawings is, conventionally, centered on an optical axis 2, and has a convex anterior face 3 and a concave posterior face 4.

This last face is spherical while the front face 3 has a complex shape allowing, in combination with the rear face 4, to provide the vision correction required for the wearer, and also to provide stabilization, both at centering and at rotation. , of this lens vis-à-vis the eye, thanks to the dynamic effect regularly caused by blinking of the eyelids.

More specifically, the vision correction is provided by the zone 5 located between the optical axis 2 and the circle located 4 mm from this axis, shown in broken lines in the drawings, while the stabilization means consists of well known manner, by a progressive thinning or lightening, towards the edge, respectively of the upper portion 6 and the lower portion 7 of the lens, in the vertical direction (axis of the blinking of the eyelids), the portions 6 and 7 cooperating respectively with the upper eyelid and with the lower eyelid, so that the axis 2 coincides with the optical axis of the wearer's eye and so that the horizontal meridian plane 8 of the lens 1 coincides with the horizontal meridian plane of l eye of the wearer.

The illustrated lens is intended to operate an astigmatism correction according to a plane of symmetry 9 (FIG. 3) having an angular deviation φ with respect to the horizontal meridian plane 8, to operate a myopia or hyperopia correction as well as to operate a correction of presbyopia with progressive simultaneous vision.

Either at any point on the anterior surface 3 of the lens. Its position is defined by the coordinates h and θ, h being the distance separating point A from the optical axis 2 of the lens and θ the angular difference between the meridian plane containing point A and the reference plane 8.

Because the shape of the posterior surface 4 is known (spherical in the present example), as well as the refractive index of the material of the lens, and if the thickness of the latter is fixed in the center, it is possible to determine in a well-known manner the coordinates of the different points A of the anterior surface 3 from the optical path δ (h, θ), which is chosen here, at least for h located between 0.4 mm and 2.4 mm , as answering the inequality: δ _ιnf (h, θ) ≤ δ (h, θ) ≤ δ _sup (h, θ) δ _ιnf (h, θ) and δ _sup (h, θ) responding respectively to the following equations : δ _ιnf (h, θ) = δ _{û +} δ _s (h) + δ _p (h) + δ _A (h, θ) - 0.9 h ² δ _sup (h, θ) = δ _ιnf (h, θ ) + 0.18 h ² equations in which:

- δ _ιnf (h, θ) and δ _sup (h, θ) are expressed in micrometres (μm);

- h is expressed in millimeters (mm);

- θ is expressed in radian (rad);

- δo is an arbitrary constant;

- δ _s (h) is, in the case of spherical correction, the optical path provided for this correction, corresponding to the equation:

equation in which P _VL is the power required to correct myopia or hyperopia of said eye, expressed in diopters (D); δ _p (h) is the optical path provided for the correction with progressive simultaneous vision, corresponding to the equation:

δ _p (h) = ∑ ^ h- ²

the series of coefficients α ₂ , being defined by a respective of the nine lists SA, SB, SC, MA, MB, MC, LA, LB, LC of coefficients below:

(E and the number following it represent the exponent in power of 10); and δ _A (h, θ) is the optical path provided for the toric correction, corresponding to the equation:

δ _A (h, θ) = | h ² sin ² (θ -φ)

equation in which C is the cylinder power required to correct the astigmatism of said eye, expressed in diopters (D).

The optical path thus defined makes it possible to determine a shape which is suitable for the anterior surface of the corrective portion 5. In another variant, the correction of presbyopia, rather than being carried out as in lens 1 with greater power at the center than at the periphery of the corrective portion 5, is carried out with a variation in the opposite direction, it that is to say with a power which is less important at the center than at the periphery of the corrective portion.

In such a case, the optical path introduced by the correction with progressive simultaneous vision is not that given above, but:

P _ADD being the addition required by the wearer of the lens for near vision, expressed in diopters (D), the series of coefficients α _2l being defined by a respective one of the nine lists SA, SB, SC, MA, MB, MC, LA, LB, LC given above.

In another variant of the lens 1, the posterior face 4, instead of being purely spherical, has an aspherical shape which is mechanically adapted to the geometry of the cornea of the eye intended to receive this lens, this posterior surface being in practice chosen in a series of predetermined shapes, from tests carried out on the eye to be fitted.

In other variants not shown, the reliefs 6 and 7 are replaced by different centering and rotation stabilization means, and in particular by dynamic bumps as described in French patent 2,760,853 or by a ballast prism located in lower part, possibly supplemented by a reduction in the upper part.

It will be observed that the preparation of an ophthalmic lens according to the invention is relatively simple, since it suffices to determine the optical path to be introduced by the corrective portion of the lens according to the optometric examination of the wearer of the lens, to select the shape of the posterior surface which provides the wearer with optimum comfort, to determine from these elements the shape of the anterior surface, then to manufacture the lens, of which only the anterior face is complex. In yet another variant not shown, the lens is not a contact lens, but an intraocular implant, and is therefore not provided with centering and rotation stabilization means.

Many other variants are possible depending on the circumstances, and it is recalled in this regard that the invention is not limited to the examples described and shown.

Claims

1. An ophthalmic lens comprising a corrective portion for correcting the vision provided by an optionally myopic or hyperopic astigmatic eye, provided so that a reference meridian of said lens remains aligned with a predetermined meridian of said eye; characterized in that said lens also corrects presbyopia and in that said corrective portion has an anterior surface and a posterior surface one of which, called the first surface, is spherical or aspherical mechanically adapted to the geometry of said eye and the other of which , called the second surface, has a complex shape 0 offering both a correction of presbyopia with progressive simultaneous vision, a correction of astigmatism and possibly a correction of myopia or spherical hyperopia, so that the combination of the first surface and of the second surface introduces a varying optical path, as a function of the distance from the optical axis and as a function of the angular deviation from said reference meridian, at least when this distance is between 0.4 mm and 2, 4 mm, according to a distribution falling within a zone comprised between a lower envelope surface and an envelope surface upper pe, corresponding respectively to the following equations: _Q δ _ιnf (h, θ) = δ ₀ + δ _s (h) + δ _p (h) + δ _A (h, θ) - 0.9 h ² δ _sup (h , θ) = δ _ιnf (h, θ) + 0.18 h ² equations in which:

- δ, _nf (h, θ) and δ _sup (h, θ) are expressed in micrometres (μm);

- h is the distance from the optical axis, expressed in millimeters (mm); 5 - θ is the angular deviation from said reference meridian, expressed in radian (rad);

- δo is an arbitrary constant;

- δ _s (h) is, in the case of spherical correction, the optical path provided for this correction, varying as a function of the distance h relative to 0 the optical axis; - δ _p (h) is the optical path, varying as a function of the distance h from the optical axis, provided for correction with progressive simultaneous vision; and

- δ _A (h, θ) is the optical path provided for the correction of astigmatism.

2. Lens according to claim 1, characterized in that the term δ _A (h, θ) corresponds to the equation:

δ _A (h, θ) = h ² sin ² (θ - φ)

3. Lens according to any one of claims 1 or 2, characterized in that the term δs (h) corresponds to the equation:

δ _s (h) = ^ h ²

equation in which P _VL is the power required to correct myopia or hyperopia of said eye, expressed in diopters (D).

4. Lens according to any one of claims 1 to 3, characterized in that the term δ _P (h) corresponds to the following equation: ι = 9, _{δ (} h) = y - ^ - h ^{2ι + 2} ^P 1 & 2i + 2 the series of coefficients α ₂ j being defined by a respective one of the nine lists SA, SB, SC, MA, MB, MC, LA, LB, LC of coefficients below:

(E and the number following it represent the exponent in power of 10)

5. Lens according to any one of claims 1 to 3, characterized in that the term δ _P (h) corresponds to the following equation: ADD α-, δ _P (h) = ^h! - ∑ -h 2ι + 2

2 ^ 2i + 2

P _ADD being the addition required by the wearer of said lens for near vision, expressed in diopters (D), the series of coefficients α ₂ , being defined by a respective one of the nine lists SA, SB, SC, MA, MB , MC, LA, LB, LC of coefficients below:

(E and the number following it represent the exponent in power of 10)

6. Lens according to any one of claims 1 to 5, characterized in that it constitutes an intraocular implant.

7. Lens according to claim 6, characterized in that said first surface is spherical.

8. Lens according to any one of claims 1 to 5, characterized in that it constitutes a contact lens.

9. Lens according to claim 8, characterized in that said first surface is spherical.

10. Lens according to claim 8, characterized in that said first surface is part of the rear face of the contact lens while said second surface is part of its front face.

11. Lens according to claim 10, characterized in that said first surface is spherical or aspherical adapted mechanically to the geometry of the cornea of said eye.

12. Lens according to any one of claims 8 to 11, characterized in that it comprises on its anterior face a stabilization means adapted to maintain said reference meridian of said lens aligned with said predetermined meridian of said eye.

13. Lens according to claim 12, characterized in that said stabilization means is with dynamic bumps.

14. Lens according to claim 12, characterized in that said stabilization means is double relief.

15. Lens according to claim 12, characterized in that said stabilization means comprises a ballast.

16. A method of preparing an ophthalmic lens according to any one of claims 1 to 15, characterized in that it comprises: a) a step of determining the optical path to be introduced by the corrective portion of this lens; b) a step of selecting the shape of the posterior surface of said corrective portion, from a series of predetermined shapes, in order to provide the wearer of the lens with optimum comfort; c) a step of determining the shape of the anterior surface of said corrective portion, from said shape selected for the surface posterior to step b) and the optical path determined in step a); and d) a step of manufacturing said lens with said corrective portion which has the anterior surface and the posterior surface thus determined.