Ophthalmic lens usable for a range of distinct prescription axes

Abstract

The invention relates to an ophthalmic lens (10) having a rotating point and a vertical line (VL) passing through said rotating point, and providing at a far vision point (FVP) at least a non-zero cylindrical power oriented according to a nominal cylinder axis relative to said vertical line and in a near vision area (11) a non-zero addition of spherical power. According to the invention, said ophthalmic lens is suitable for a range of prescriptions of cylinder axis of at least 20° about said nominal cylinder axis.

Description

[0001] OPHTHALMIC LENS USABLE FOR A RANGE OF DISTINCT PRESCRIPTION AXES

[0002] TECHNICAL FIELD

[0003] The present description generally relates to the field of eyeglasses.

[0004] It more particularly deals with reducing waste during ophthalmic lens manufacturing.

[0005] BACKGROUND INFORMATION AND PRIOR ART

[0006] A traditional method for manufacturing an ophthalmic lens can consist in:

[0007] - providing two molding shells at the periphery of which is disposed an annular closure member (such as a tape), which member defines with these shells a molding cavity (the use of this tape being not mandatory),

[0008] - molding a lens blank by filling this molding cavity with a monomer and by polymerizing this polymer,

[0009] - machining one of the surfaces of this blank to obtain a lens that fulfills the optical function for which it has been designed.

[0010] The two molding shells are used to mold several lens blanks and therefore to manufacture lenses of distinct shapes.

[0011] The difference of shapes between the lens blank and the machined lens is generally great. Indeed, the blank must have a sufficiently large thickness so as to be used to manufacture lenses of various shapes.

[0012] In other words, a lot of material is needed to mold lens blanks. And a large amount of material has to be removed during the machining step. It is not uncommon that the weight of the lens blank is 5 times greater than the weight of the finished lens.

[0013] This problem could be avoided with smaller blanks, but this solution would require a large number of molding shells and annular close members of distinct shapes, that would not be, in practice, manageable.

[0014] Moreover, the storing of such blanks would be complicated because of the large number of references.

[0015] SUMMARY

[0016] In this context, the present application provides a solution for manufacturing an ophthalmic lens that enables stocking lenses, that minimizes the required volume of material to manufacture these lenses and that eliminates the need for surfacing the lenses.. The invention relates to an ophthalmic lens:

[0017] - having a vertical line, and

[0018] - providing at a far vision point at least a non-zero cylindrical power oriented according to a nominal cylinder axis relative to said vertical line and in a near vision area located around a near vision point a non-zero addition of spherical power,

[0019] - suitable for a range of prescriptions of cylinder axis of at least 20° about said nominal cylinder axis (i.e. at least 10° on each side of the nominal cylinder axis).

[0020] Thanks to the invention, a single reference of lens can be used for distinct prescriptions of cylinder axes since that lens is shaped so as to be able to be rotated within a defined range of orientations, while fulfilling the optical function for which it has been designed.

[0021] Consequently, the number of references of lenses to store is reduced, so that it becomes possible to stock a limited number of lenses.

[0022] To summarize, it is therefore possible to stock finished ophthalmic lenses that will satisfy a great part of the wearers' prescriptions. As a result, these lenses will be able to be delivered without delay to the optician so that the latter can machine their edge to engage them in the frame rims.

[0023] Ideally, lenses for all possible prescriptions could be stocked. But in practice, only the lenses meeting the most common prescriptions will be stored, the other lenses being manufactured on demand.

[0024] Other preferred features of the invention are the following ones:

[0025] - the cylindrical power provided by the ophthalmic lens being homogeneous within said near vision area, whatever a tilted line passing through said near vision area and tilted about said rotating point relative to said vertical line in angular range of at least 10° on each side of said vertical line, said near vision area has a maximum width on one side of said tilted line that is greater than 10° and preferably greater than 15°;

[0026] - Preferably:

[0027] Wm = tan- 10° V R e [-10°; 10°]

[0028] Wm being the maximum width (in degrees),

[0029] Xvp being the distance between the near vision point and the rotating point measured along an axis orthogonal to the vertical line, Yvp being the distance between the near vision point and the rotating point measured along the vertical line,

[0030] R being the angle between said tilted line and said vertical line, and Cn being a design parameter;

[0031] - Preferably: tan( / ? + R) * Yvp E [0mm; 7mm] V R G [—10°; 10°]

[0032] [3 being the angle between said vertical line and the axis passing through said rotating point and said near vision point,

[0033] R being the angle between said tilted line and said vertical line, and

[0034] Yvp being the distance between the near vision point and the rotating point measured along the vertical line.

[0035] - Preferably: tan( / ? + R) * Yvp E [0mm; 5mm] V R E [—10°; 10°]

[0036] - said angular range is of at least 30°, and preferably of at least 40°;

[0037] - said rotating point is the far vision point or a fitting point or a prism reference point of the ophthalmic lens;

[0038] - a distance between said rotating point of the ophthalmic lens and a point of the near vision area is at most equal to 8 mm and preferably at most equal to 7 mm;

[0039] - the ophthalmic lens comprises at least one marking showing a position of the rotating point;

[0040] - said nominal cylinder axis is inclined relative to a vertical line of the lens of 90° or 180°, within 10°;

[0041] - the ophthalmic lens has a progressive addition of spherical power between the far vision point and the near vision area;

[0042] - said addition is at most equal to 1 dioptre;

[0043] - the ophthalmic lens is bifocal;

[0044] - the ophthalmic lens comprises at least one marking having a shape and / or a position depending on said maximum width;

[0045] - at least two markings locate extremities of said near vision area or the maximum inclination of said tilted line.

[0046] The invention also relates to a method for delivering an ophthalmic lens, comprising:

[0047] - a step of acquiring a prescription defined at least by a non-zero cylindrical power requirement and a cylinder axis requirement,

[0048] - a step of providing an ophthalmic lens giving at a far vision point a cylindrical power equal to said cylindrical power requirement and oriented according to a nominal cylinder axis tilted from said cylinder axis requirement of at least 10°, and

[0049] - a step of centering the ophthalmic lens, comprising the orientation of the ophthalmic lens relative to the cylinder axis according to the cylinder axis requirement.

[0050] In a preferred embodiment, this method comprises, before said steps:

[0051] - a step of designing the shape of the ophthalmic lens with a rotating point and a vertical line passing through said rotating point, and with: n at a far vision point, at least a non-zero cylindrical power oriented according to a cylinder axis, n in a near vision area, a non-zero addition of spherical power, the cylindrical power provided by the ophthalmic lens being homogeneous within said near vision area, whatever a tilted line passing through said near vision area and tilted about said rotating point relative to said vertical line in angular range of at least 10° on each side of said vertical line, said near vision area has a maximum width on one side of said tilted line that is greater than 10° and preferably greater than 15°, and

[0052] - a step of manufacturing the ophthalmic lens.

[0053] In a preferred embodiment, the steps of designing and manufacturing are performed so as to manufacture a stock of ophthalmic lenses, at least two of said ophthalmic lenses having distinct cylinder axes, and before the step of centering, a step of selection is carried out to select an ophthalmic lens having a cylinder axis suitable with the cylinder axis requirement.

[0054] In a preferred embodiment, during the step of designing, a distance is imposed between the near vision area and a rotating point of the ophthalmic lens, said rotating point being for instance the far vision point or a fitting point or a prism reference point of the ophthalmic lens.

[0055] In a preferred embodiment, said distance is at most equal to 9 mm and preferably at most equal to 8 mm.

[0056] DETAILED DESCRIPTION OF EXAMPLE(S)

[0057] The following description with reference to the accompanying drawings, given by way of non-limiting example makes it clear what the invention consists in and how it can be reduced to practice. In the accompanying drawings:

[0058] - Figures 1 to 5 represent mappings of distribution of spherical power (left) and cylindrical power (right) of five ophthalmic lenses according to the art, for prescriptions of - 4.5 diopters of spherical power, 2 diopters of cylindrical power, addition of spherical power of 0.6 diopters and for cylinder angles of respectively 0°, 170°, 10°, 160°, 20°, and

[0059] - Figure 6 is a schematic representation of an ophthalmic lens according to the invention;

[0060] - Figures 7 and 8 are schematic representations of the ophthalmic lens of Figure 6, tilted with two distinct orientations.

[0061] In Figure 6, we have represented an ophthalmic lens 10.

[0062] This lens may be a progressive addition lens, a bifocal lens or an antifatigue lens (which is a kind of progressive addition lens for which the addition is at most equal to 1 dioptre). Here the lens is preferably of the anti-fatigue kind.

[0063] Such an ophthalmic lens 10 has an initial contour of circular shape that is to be machined, so that this lens can be mounted in a rim of an eyeglass frame.

[0064] The optical correcting power of a correcting ophthalmic lens is defined by its spherical, cylindrical, and prismatic properties. It will be understood that such an optical definition is of a scope that is more general than a definition of surfaces only: it defines the overall refringence effect of the lens on an incident light ray, which results from the algebraic sum of the refringences imparted successively by both the front and the rear faces of the lens. It will be understood that such an optical definition covers a plurality, or even an infinity, of combinations of pairs of surfaces producing the same overall optical refringence effect, as explained in the document “Theoretical aspects of concentric varifocal lenses” by W. N. Charman, in Opthal. Physiol. Opt., Vol. 2, No. 1 , pp. 75-86, 1982, published by Pergamon Press for the British College of Ophthalmic Opticians.

[0065] Among these refringence properties, the first to be defined is the “spherical refringence” power of a lens for an incident beam passing through the lens (also known as the total power or refringent power or focusing power or spherical optical power). It is defined as the magnitude that characterizes and quantifies the primary effect of spherical refringence (“magnifying glass” effect) of the lens on the beam under consideration: if it is positive, the lens has a converging effect on the beam; if it is negative, the effect on the beam is diverging. The point of the lens where the magnifying glass effect is zero (i.e., for a lens having optical power that is purely spherical, the point where the incident ray and the transmitted ray have the same axis) is known as the “optical center”.

[0066] The term “cylindrical refringence power” of a lens is defined, for an incident ray passing through the lens (also known as the cylindrical optical power), as being the magnitude that characterizes and quantifies the cylindrical refringence effect exerted by the lens on the ray under consideration, whereby not one but two focal areas are formed that are situated in different planes, which focal areas are generally mutually perpendicular and referred to as the tangential focus and the sagittal focus. This cylindrical power, also known as “astigmatism power” or merely as “astigmatism”, corresponds to the difference between the spherical powers associated with the two focal areas. The two areas are identified by an axis passing through their “optical centers” and commonly referred to as the “nominal cylinder axis” Cyax. In practice, according to the TABO standard, a nominal cylinder axis is defined by an angle a between this cylinder axis Cyax and an horizontal line HL of the lens.

[0067] The horizontal line HL and a vertical line VL are defined relative to the ophthalmic lens 10. These lines HL, VL are axes relative to which the lens will be centered. In other words, the boxing system (that is a rectangle circumscribing the outline along which the lens edge will me machined) will be oriented relative to these horizontal and vertical lines HL, VL. Consequently, when the lens will be fitted in an eyeglass frame and worn, the vertical line VL will be located in a vertical plane (when the head of the wearer will be straight) and the horizontal line HL will be located in a horizontal plane.

[0068] In Figure 6, the nominal cylinder axis Cyaxand the vertical line VL are superimposed. Consequently, the angle of this nominal cylinder axis is of 90°.

[0069] Finally, the “prismatic refringence power” of a lens is defined, for an incident ray passing through the lens (also known as the prismatic optical power), as being the magnitude that characterizes and quantifies the prismatic refringence effect, or more simply the deflection exerted by the lens on the ray under consideration. This prismatic power, also known as “prism”, corresponds to the angle through which the ray is deflected, i.e. the angle formed between the entry and exit portions of the ray. The prism is made up of two components: a horizontal component referred to as the “horizontal prism” corresponding to the angle formed between the protrusions of the incoming and outgoing portions of the ray onto a horizontal plane, and a vertical component, referred to as the “vertical prism” corresponding to the angle formed between the protrusions of the incoming and outgoing portions of the ray onto a vertical plane. In the following, the “prism reference point” PRP will be the point where the prism is defined and can be measured. In practice, it is here the geometrical center of the ophthalmic lens.

[0070] We can also define a far vision point and a near vision point.

[0071] The far vision point FVP refers to the point through which the eye is focused when it is in a relaxed state, typically looking at objects that are far away.

[0072] The near vision point NVP refers to the closest point through which the eye can comfortably focus on an object with clear vision. The distance, measured along the vertical line, between this near vision point NVP and the prism reference point PRP is referenced YVP. The same distance, measured along the horizontal line, is referenced XVP. The angle between the vertical line VL and the axis passing through the near vision point NVP and the prism reference point PRP is referenced [3.

[0073] Consequently, we can write: tan(|3) = XVP I YVP

[0074] The addition is the spherical power difference between the far vision point FVP and the near vision point NVP.

[0075] The fitting point FP is the point on the front surface of the lens defined as reference point for positioning the lens in front of the eye.

[0076] The ophthalmic lens has a rotating point 10. In the following, we will consider that this rotating point coincides with the prism reference point PRP.

[0077] In a variant, the rotating point could be the far vision point FVP or the fitting point FP of the lens or the geometrical center of the lens. In a more general manner, it could be a point marked on the lens and located in the central part of the lens (within a radius of 25% maximum of the lens radius, around the geometric center of the lens).

[0078] We can also define the mean plane of the ophthalmic lens as the plane minimizing the sum of the deviations (according to the least squares method) of the points on the lens front and back surfaces from the plane.

[0079] An ophthalmic lens 10 can be defined by several features, among which:

[0080] - a spherical power Ps at the far vision point FVP,

[0081] - a cylindrical power Pc at the far vision point FVP,

[0082] - a nominal cylinder axis angle a at the far vision point FVP, - an addition Ad of spherical power.

[0083] We also can define a far vision zone as a circular region of the lens centered on the far vision point FVP, extending over a diameter ranging from approximately 8 mm to 10 mm, and in which the spherical power Ps remains substantially constant, exhibiting variations generally less than 0.12 diopters. This is the area within which it is usual to check the optical power of the lens (at least its spherical power) using a focimeter.

[0084] In Figures 1 to 5, we have represented examples of mappings of distribution of spherical power (left view in each figure) and cylindrical power (right view in each figure) of five ophthalmic lenses according to the art. All these lenses have an addition of 0.6 diopter, a spherical power at the far vision point FVP of - 4.5 diopters and a cylindrical power of 2 diopters. They respectively have a cylinder axis angle of O° (Fig.1 ), 170° (Fig.2), 10° (Fig.3), 160° (Fig.4), 20° (Fig.5).

[0085] In each of these figures the curves in solid lines represent the isoline of spherical power (on the left mapping) or the isoline of cylindrical power (on the left mapping).

[0086] The curves in dotted line represent the medians, that is to say the lines corresponding to the middle of the isolines.

[0087] In Figures 1 to 5, it is clearly shown that, in a little area located around the near vision point NVP, the spherical power increases only a little (in a direction oriented from the center toward the edge of the lens) and that the cylindrical power is homogeneous.

[0088] This area is quite stable in power and astigmatism.

[0089] Here, the term homogeneous refers to an area in which the gap between the maximum cylindrical power and the minimum cylindrical power is little and fewer than a predefined value. This value is at most equal to 0.5 diopter. It is here equal to 0.25 diopter.

[0090] In this area, called hereinafter near vision area 11 , the spherical power is preferably also homogeneous in the sense in that the gap between the maximum spherical power and the minimum spherical power is little and fewer than a predefined value. This value is at most equal to 0.5 diopter. It is here equal to 0.25 diopter.

[0091] This near vision area 11 can be associated to the zone of the lens used by the wearer to observe objects at a little distance, for instance to read books. This homogeneous near vision area has a non-null width and height because the wearer eye gaze is not fixed but it moves a little relative to the ophthalmic lens 10.

[0092] Because this near vision area 11 is little in the lenses of the art, these ophthalmic lenses have to be properly centered to ensure the near vision point to be exactly located and the near vision area 11 to be usable by the wearer.

[0093] Indeed, in Figures 1 to 5, we observe very clearly that the cylindrical power distributions are very different even for two lenses having cylinder axes inclined by only 10°. Hence, a lens having a nominal cylinder axis angle a of 20° for example cannot be used for a person having a cylinder axis prescription of 10°.

[0094] On the contrary, the aim of the present application is to design the ophthalmic lens 10 in such a manner that this lens is usable for a range Ra of prescriptions of cylinder axis angle of at least 20°. This range is preferably of at least 30° and more preferably of at least 40°.

[0095] In other words, the ophthalmic lens 10 is designed so that its vertical line VL can be tilted from at least 10° relative to a vertical plane (on both sides of this plane) once mounted in the corresponding frame rim. Therefore, the boxing system will be tilted of at least 10 degrees relative to this vertical line VL.

[0096] Consequently, the ophthalmic lens 10 is designed so that the angle between the cylinder axis prescription arand the nominal cylinder axis angle a of the lens can be equal to at least 10°.

[0097] To this end, the lens will be centered by no longer considering its vertical line VL to orient the boxing system, but rather by considering a tilted line TL inclined relative to this vertical line.

[0098] The angular range Ra delimits the maximum inclination between the prescribed cylinder axis and the nominal cylinder axis Cyax of the lens.

[0099] This inclination will be carried out around the rotating point (here the PRP point), in the mean plane of the lens.

[0100] In Figures 7 and 8, we have represented the lens of Figure 6 oriented no longer relative to the vertical line VL, but relative to a tilted line TL inclined in one direction or the other with respect to the vertical line VL.

[0101] We understand that once the lens is tilted in one direction or the other (in the range Ra), the far vision point FVP of the lens will be slightly offset from the effective point through which the eye will be focused when it is in a relaxed state, typically looking at objects that are far away. But because the distance between the far vision point FVP and the rotating point PRP is little and because the area around the far vision point is quite stable in power, this offset will be small enough to have no impact on the comfort and effectiveness of the lens.

[0102] The same is not true for the near vision point NVP which, for its part, is located at a great distance from the center of rotation (the rotating point PRP) and which is in the state of the art not stable in power and astigmatism.

[0103] Indeed, when tilting the lens, the near vision point NVP and the near vision area 11 move around the rotating point.

[0104] Consequently, when the wearer will read books, the direction of his gaze risks passing through a point out of this area, so that the spherical and cylindrical powers Ps, Pc will no longer be adequate.

[0105] The present application then consists in designing the lens so as to avoid this problem.

[0106] One of the solutions consists in widening the near vision area 11 . The other solution consists in limiting the distance between the center of the rotation (the rotating point PRP) and this zone.

[0107] As shown in Figure 6, to define this near vision area 11 , we could specify its vertical position (YVP) and its total maximum width Wmo.

[0108] This total maximum width Wmo is the length of the near vision area 11 (where the cylindrical power Pc is homogeneous) measured orthoradially to the rotating point or the opening angle of the angular sector centred on the rotating point and delimited between the two lines passing through the centering point and one or the other of the extremities of the near vision area 11 .

[0109] This total maximum width Wmo is preferably greater than 15° and more preferably greater than 20°.

[0110] This value is expressed in degrees around the rotating point but in a variant, it could be expressed in millimeters (taking into account an average distance of 25 mm between the center of rotation of an eye and a lens fitted in an eyeglass frame and worn).

[0111] Here, this definition is completed for the following reason.

[0112] The part of the near vision area 11 that will be used by the wearer is located on only one side of the vertical line VL (by considering that the lens is not tilted relative to the vertical line VL). Indeed, when reading at little distance, the eyes directions of the wearer eyes gazes converge. When looking at far distance, these directions are rather parallel. But they never diverge so that the part of the lens located on the temporal side of the vertical line (the left side for a left lens and the right side for a right lens) are never used when the wearer looks an object at little distance (provided that the object is located in front of the wearer, that is to say in his sagittal plane).

[0113] In the following, the inner side of the lens will be defined as the side relative to the vertical line VL that is to be located on the side of the nose of the wearer (the left side for a right lens and the right side for a left lens).

[0114] So we may characterize the near vision area 11 by a usable maximum width Wm that is the length of the near vision area 11 of the lens:

[0115] - measured about the rotating point,

[0116] - where the cylindrical power Pc is homogeneous, and

[0117] - that is located in the inner side of the lens (relative to the vertical line VL).

[0118] This usable maximum width Wm is preferably greater than 15 °and more preferably greater than 20°.

[0119] But the aim of the present application is to use the lens for prescriptions of cylinder axis angle (named “cylinder axis requirement ar”) distinct from the nominal cylinder axis angle a of the lens (but comprised into the range Ra), by rotating the lens around the rotating point of an angle R (see Figs. 8 & 9).

[0120] Consequently, the definition relative to the vertical line VL can be not sufficient. Indeed, the part of the near vision area 11 that will be used by the wearer is not limited to the inner side of the lens if the lens is tilted.

[0121] That is why we rather have to consider the tilted line TL that passes through the near vision area 11 , that is tilted relative to said vertical line VL and that will become a new vertical line once the lens tilted (the boxing system being oriented relative to this tilted line TL).

[0122] Consequently, another definition of the maximum width Wm functional for any tilted line TL comprised into the range Ra can be established.

[0123] This maximum width Wm is the length of the near vision area 11 (preferably expressed in degrees) that:

[0124] - is measured about the rotating point,

[0125] - where the cylindrical power Pc is homogeneous, and

[0126] - that is located in the nose side of the lens relative to the tilted line TL.

[0127] This maximum width Wm can be expressed by an opening angle of an angular sector centred on the rotating point and delimited between the tilted line TL and the extremity of the near vision area 11 (the one that is located in the nose side of the lens).

[0128] Such a maximum width Wm can be determined for any angle R between the tilted line TL and the vertical line VL within the angular range Ra of at least 20° (10° on each side of the vertical line VL) about said rotating point.

[0129] According to the present description, whatever the tilted line TL, this maximum width Wm is greater than 10° and more preferably greater than 15°.

[0130] Consequently, we can write: 10°

[0131] VR E [— 10°; 10°] and preferably V R E [—15°; 15°] and more preferably V R E [—20°; 20°]

[0132] In this equation, Cn is a design parameter shown in Figure 6, corresponding to the width (in degrees about the rotating point) of the part of the near vision area 11 located on the nose side of the near vision point. The lens has to be shaped so that this parameter fulfils the above equation.

[0133] When the lens is not tilted (with R=0), the near vision point NVP must be located at a limited distance from the vertical line VL. It is the same when the lens is tilted (with R + 0). Consequently, the lens has to be shaped such that the distance 1st between the near vision point NVP and the vertical line VL is such that:

[0134] 1st = tan( / ? + R) * Yvp E [0mm; 7mm]

[0135] V R E [— 10°; 10°] and preferably V R E [—15°; 15°] and more preferably V R E [—20°; 20°]

[0136] In a preferred embodiment, tan( / ? + R) * Yvp E [0mm; 5mm] V R E [— 10°; 10°] and preferably V R E [—15°; 15°] and more preferably V R E [—20°; 20°]

[0137] Advantageously, the distance YVP between the rotating point and the near vision point NVP is less than or equal to 8 mm and preferably is less than or equal to 7 mm. Indeed, the greater this distance is, the more the near vision area 11 will be shifted when rotating the lens. That is why this constraint is given when designing the lens.

[0138] As an example, we can give example values of lens parameters that fulfil the required constraints.

[0139] The practical objective of the application is to allow lenses to be stored so as not to be forced to manufacture them on demand.

[0140] Because before the solution of the present application it was necessary, for each prescription of spherical power, cylindrical power and addition, to store as many lenses as there are possible cylinder axes (typically 180), the number of references to store was too large to be manageable.

[0141] Thanks to the application, if a lens is usable for an angular range of 40°, it is possible to reduce said number of references to be stored at 360740° = 9.

[0142] However, it turns out to be complicated to sock nine lenses for each prescription of spherical power and cylindrical power.

[0143] And the applicant noticed that, in the majority of cases, the cylinder axis requirements arare comprised between 70° and 110°, and between 160° and 20°.

[0144] This is the reason why only two lens references have been designed according to the present description: one reference with a nominal cylinder axis of 0° and another with a nominal cylinder axis of 90° (each reference being able to be used in a range Ra of 40°). Thus, only these two lens references are stored. The others, however, are manufactured on demand with a cylinder axis equal to the cylinder axis requirement.

[0145] Alternatively, four lens references could be designed according to the present application, namely references with nominal cylinder axes of 170°, 10°, 80° and 100° (each reference being able to be used in a range Ra of 20°).

[0146] It is known to make markings on the lenses so as to facilitate their centering, that is to say the positioning on the lens of the boxing system and of the contour according to which the lens has to be cut out so as to be able to be mounted on a spectacle frame.

[0147] These markings can be made in various ways and in different forms; they can thus be engraved on the lens or drawn, using erasable ink.

[0148] We will consider here that the markings are of this second type.

[0149] As a general rule, it is planned to make a dot or a cross at the fitting point FP, as well as points or lines allowing the horizontal line of the lens to be identified (which line is perpendicular to the vertical line VL at the fitting point FP).

[0150] Other markings may be provided, such as a cross indicating the prism reference point PRP.

[0151] In the context of the invention, it is also provided at least one marking having a shape and / or a position depending on said maximum width Wm.

[0152] For instance, one marking could represent the value, in degrees, of the angular range Ra.

[0153] But here, it is provided exactly two markings 12, 13 illustrating this angular range Ra.

[0154] These markings could locate the extremities of the near vision area 11 .

[0155] But here, they are positioned so as to identify the range Ra in which the tilted line TL can be located.

[0156] In practice, these markings are formed by points or lines delimiting in what extent it is possible to rotate the lens about the rotating point PRP.

[0157] The invention also relates to a method for delivering such an ophthalmic lens 10.

[0158] This method is carried out in two main operations.

[0159] The first operation comprises a first step that consists in designing the shape of two ophthalmic lenses 10 as described above, with: n at a far vision point FVP, at least a non-zero cylindrical power Pc oriented according to a nominal cylinder axis angle a, n in a near vision area 11 , a non-zero addition Ad of spherical power Ps, and an homogeneous cylindrical power.

[0160] As explained above, during this step of designing, a maximum width Wm and a distance YVP (between the near vision area 11 and the rotating point of the ophthalmic lens 10) are imposed.

[0161] The two ophthalmic lenses 10 differs only by their nominal cylinder axis angles a. Here, one of them has a cylinder axis oriented at 0° when the other one has a cylinder axis oriented at 90° relative to their vertical line VL.

[0162] In practice, many other couples of lenses are designed, for distinct spherical and cylindrical powers Ps, Pc.

[0163] But in the following, we will consider only this couple of lenses, both of which having the same spherical and cylindrical powers Ps, Pc.

[0164] The first operation comprises a second step of manufacturing the ophthalmic lenses 10.

[0165] Here many lenses are manufactured to be stored.

[0166] The first operation is performed when the future wearers of the lenses are not already known.

[0167] On the contrary, the second operation is carried out when a future wearer of a lens is identified.

[0168] The first step of this second operation consists in acquiring a prescription Pres of the wearer.

[0169] This prescription is generally delivered by an optometrist.

[0170] Here, this prescription Pres is defined by four values:

[0171] - a spherical power requirement Psrat the far vision point FVP,

[0172] - a cylindrical power requirement Pcrat the far vision point FVP,

[0173] - a cylinder axis requirement ar,

[0174] - an addition requirement Adrof spherical power.

[0175] Then, it is searched whether a convenient ophthalmic lens 10 is stored.

[0176] To this end, it is determined if it is stored a lens having:

[0177] - a spherical power Ps equal to the requirement Psrat the far vision point

[0178] FVP,

[0179] - a cylindrical power Pc equal to the requirement Pcrat the far vision point

[0180] FVP,

[0181] - a nominal cylinder axis angle a equal to the requirement ar,

[0182] - an addition Ad equal to the requirement Adrof spherical power.

[0183] If yes, this lens is selected and centered according to a usual method.

[0184] Else, it is determined if it is stored a lens having:

[0185] - a spherical power Ps equal to the requirement Psrat the far vision point

[0186] FVP,

[0187] - a cylindrical power Pc equal to the requirement Pcrat the far vision point FVP,

[0188] - an addition Ad equal to the requirement Adrof spherical power, and

[0189] - an angular range Ra centered on said nominal cylinder axis Cyax such that the requirement aris comprised in it. If not, the manufacture of a new lens is ordered and this lens is then centered according to a usual method.

[0190] Else, this lens is selected and centered according to an unusual method.

[0191] To this end, during this centering step, the outline along which the lens has to be edged is superimposed onto an image of the lens, such that a pupillary point (defined relative to the outline) is located on the fitting point.

[0192] This outline is oriented such that two sides of the boxing system are not parallel to the vertical line VL by inclined relative to this line by an angle equal to the angle between the nominal cylinder axis Cyax and the requirement ar.

[0193] Then, the lens edge is machined along this outline, and the lens is mounted on the wearer’s frame.

[0194] The present invention is in no way limited to the embodiment described and shown.

Claims

CLAIMS1 . An ophthalmic lens (10) having a vertical line (VL) and providing at a far vision point (FVP) at least a non-zero cylindrical power (Pc) oriented according to a nominal cylinder axis (Cyax) relative to said vertical line (VL) and in a near vision area (11 ) located around a near vision point (NVP) a non-zero addition (Ad) of spherical power (Ps), characterized in that said ophthalmic lens (10) is suitable for a range of prescriptions (Pres) of cylinder axis of at least 20° about said nominal cylinder axis (Cyax).

2. The ophthalmic lens (10) according to claim 1 , wherein, the vertical line (VL) passing through a rotating point, the cylindrical power (Pc) provided by the ophthalmic lens (10) being homogeneous within said near vision area (11 ), whatever a tilted line (TL) passing through said near vision area (11 ) and tilted about said rotating point relative to said vertical line (VL) in angular range (Ra) of at least 10° on each side of said vertical line (VL), said near vision area (11 ) has a maximum width (Wm) on one side of said tilted line (TL) that is greater than 10° and preferably greater than 15°.

3. The ophthalmic lens (10) according to claim 2, wherein:Wm = tan- 10° V R e [-10°; 10°]Wm being the maximum widthXvp being the distance between the near vision point (NVP) and the rotating point measured along an axis orthogonal to the vertical line (VL),Yvp being the distance between the near vision point (NVP) and the rotating point measured along the vertical line (VL),R being the angle between said tilted line (TL) and said vertical line (VL), and Cn being a design parameter.

4. The ophthalmic lens (10) according to anyone of claims 2 to 3, wherein: tan( / ? + R) * Yvp E [0mm; 7mm] V R G [—10°; 10°][3 being the angle between said vertical line (VL) and the axis passing through said rotating point and said near vision point (NVP),R being the angle between said tilted line (TL) and said vertical line (VL), and Yvp being the distance between the near vision point (NVP) and the rotating pointmeasured along the vertical line (VL).

5. The ophthalmic lens (10) according to anyone of claims 2 to 4, wherein said angular range (Ra) is of at least 30°, and preferably of at least 40°.

6. The ophthalmic lens (10) according to anyone of claims 2 to 5, wherein said rotating point is the far vision point (FVP) or a fitting point (FP) or a prism reference point (PRP) of the ophthalmic lens (10).

7. The ophthalmic lens (10) according to any one of claims 2 to 6, wherein a distance (YVP) between said rotating point of the ophthalmic lens (10) and the near vision point (NVP) is at most equal to 8 mm and preferably at most equal to 7 mm.

8. The ophthalmic lens (10) according to any one of claims 2 to 7, comprising at least one marking showing a position of the rotating point.

9. The ophthalmic lens (10) according to any one of claims 1 to 8, wherein said nominal cylinder axis (Cyax) is inclined relative to a vertical line (VL) of the lens of 90° or 180°, within 10°.

10. The ophthalmic lens (10) according to any one of claims 1 to 9, comprising at least one marking (12, 13) having a shape and / or a position depending on said maximum width (Wm).11 . The ophthalmic lens (10) according to claims 2 and 10, wherein at least two markings (12, 13) locate extremities of said near vision area (11 ) or the maximum inclination of said tilted line (TL).

12. A method for delivering an ophthalmic lens (10), comprising:- a step of acquiring a prescription (Pres) defined at least by a non-zero cylindrical power requirement (Pcr) and a cylinder axis requirement (ar),- a step of providing an ophthalmic lens (10) giving at a far vision point (FVP) a cylindrical power (Pc) equal to said cylindrical power requirement (Pcr) and oriented according to a nominal cylinder axis (Cyax) tilted from said cylinder axis requirement (ar) of at least 10°, and- a step of rotating the ophthalmic lens (10), comprising the orientation of the ophthalmic lens (10) relative to the cylinder axis (Cyax) according to the cylinder axis requirement (ar).

13. Method according to claim 12, comprising, before said steps:- a step of designing the shape of the ophthalmic lens (10) with a rotating point and a vertical line (VL) passing through said rotating point, and with: n at a far vision point (FVP), at least a non-zero cylindrical power (Pc) orientedaccording to a cylinder axis (CYax), n in a near vision area (11 ), a non-zero addition (Ad) of spherical power (Ps), the cylindrical power provided by the ophthalmic lens (10) being homogeneous within said near vision area (11 ), whatever a tilted line (TL) passing through said near vision area (11 ) and tilted about said rotating point relative to said vertical line (VL) in angular range (Ra) of at least 10° on each side of said vertical line (VL), said near vision area (11 ) has a maximum width (Wm) on one side of said tilted line (TL) that is greater than 10° and preferably greater than 15°, and- a step of manufacturing the ophthalmic lens (10).

14. The method according to claim 12 or 13, wherein:- the steps of designing and manufacturing are performed so as to manufacture a stock of ophthalmic lenses (10), at least two of said ophthalmic lenses (10) having distinct cylinder axes (CYax), and- before the step of rotating, a step of selection is carried out to select an ophthalmic lens (10) having a cylinder axis (CYax) suitable with the cylinder axis requirement (ar).

15. The method according to any one of claims 12 to 14, wherein, during the step of designing, a distance (YVP) is imposed between the near vision area (11 ) and a rotating point of the ophthalmic lens (10), said rotating point being for instance the far vision point (FVP) or a fitting point (FP) or a prism reference point (PRP) of the ophthalmic lens (10).

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