Method for providing a personalized spectacle lens optical system for a wearer

Abstract

A method for providing a personalized optical system for a wearer wherein the optical system characterizes a spectacle ophthalmic lens comprising the following steps: a) providing a visual performance level (VPL) value of at least one eye of the wearer; b) providing a set of rules linking at least the visual performance level of step a) with at least one optical criterion chosen among one or both of the two following optical criteria groups consisting of central vision optical criterion (CVOC) group and peripheral vision optical criterion (PVOC) group; c) calculating the physical and geometrical parameters of the personalized optical system or selecting the personalized optical system in an optical systems data base comprising a plurality of optical systems, so that to meet the set of rules of step b) according to the visual performance level data provided in step a).

Claims

1. A method at least partly implemented by computer means for providing a personalized optical system for a wearer wherein the optical system characterizes an ophthalmic lens for said wearer according to his prescription data, the method comprising the steps of: a) providing a visual performance level (VPL) value of at least one eye of the wearer, with the provision that prescription data (Rx) consisting of sphere, cylinder, axis, addition, prism are not defined as a visual performance level; b) providing a set of rules linking at least the visual performance level of step a) with at least one optical criterion chosen from at least one of the two following optical criteria groups: central vision optical criterion (CVOC) group consisting of prismatic deviation in central vision, ocular deviation, object visual field in central vision, image visual field in central vision, and magnification in central vision; peripheral vision optical criterion (PVOC) group consisting of pupil field ray deviation, object visual field in peripheral vision, image visual field in peripheral vision, prismatic deviation in peripheral vision, and magnification in peripheral vision; and c) calculating by computer means the physical and geometrical parameters of the personalized optical system that meets the prescription data of the wearer or selecting the personalized optical system in an optical systems data base comprising a plurality of optical systems that meet the prescription data of the wearer, so that to meet the set of rules of step b), wherein the rules of the set of rules refer to a link between at least a visual performance level and at least one optical criterion, and to a relationship between the said visual performance level and the said optical criterion.

2. The method according to claim 1, wherein rules of the set of rules of step b) are chosen within the list consisting of: providing a desired target value for at least a chosen optical criterion as a function of the value of the visual performance level value of step a); providing an equality or an inequality equation or a relationship between target values of the same optical criteria evaluated over at least two evaluation zones as a function of the value of the visual performance level value of step a); and providing a trend relationship between at least two chosen optical criteria as a function of the value of the visual performance level value of step a).

3. The method according to claim 2, wherein the visual performance level (VPL) of step a) is selected in the list of visual performances levels consisting of a sub-list of visual acuity performances, a sub-list of contrast sensitivity performances, a sub-list of visual space perception performance, a sub-list of reading performance, a sub-list of colour perception performance, a sub-list of self-reported visual performance, or a combination of at least two of said performances.

4. The method according to claim 3, wherein the sub-list of visual acuity performances consists of central visual acuity, peripheral visual acuity, dynamic visual acuity, each of said visual acuity being measured either according to monocular or to binocular vision and to either photopic or mesopic or scotopic vision conditions, or a combination of at least two of said visual acuity performances; and/or wherein the sub-list of contrast sensitivity performances consists of spatial contrast sensitivity, time contrast sensitivity, or a combination of said contrast sensitivity performances measured either according to monocular or to binocular vision and to either photopic or mesopic or scotopic vision conditions; and/or wherein the sub-list of “visual space perception” performances consists of distance perception acuteness, stereo acuity, aniseikonia measurement, moving object speed perception, visual field, being measured either photopic or mesopic or scotopic vision conditions, or a combination of at least two of said space perception performances; and/or wherein the sub-list of “reading performances” consists of reading rate performance, reading comprehension performance, word identification performance, being measured either according to monocular or to binocular vision and to either photopic or mesopic or scotopic vision conditions, or a combination of at least two of said reading performances; and/or wherein the sub-list of “color perception performances” consists of hue discrimination, saturation discrimination, brightness discrimination measured either according to monocular or to binocular vision and to either photopic or mesopic or scotopic vision conditions, or a combination of at least two of said color perception performances; and/or wherein the sub-list of “self-reported visual performances” consists of visual related quality of life questionnaires as national eye institute (NEI) visual functioning questionnaire or developed questionnaire on subjective visual performance during defined activities and/or defined conditions or a unique question about self-reported visual performances.

5. The method according to claim 2, wherein the visual performance levels are selected and wherein a global visual performance scale is defined.

6. The method according to claim 1, wherein the optical system is selected in optical systems data base and wherein all the optical systems of the optical systems data base have been calculating previously taking into account at least a same focalisation criterion over an evaluation zone according to at least a gaze direction.

7. The method according to claim 1 wherein the physical and geometrical parameters of step c) are calculated by computer means with an optimization method wherein at least a focalisation criterion (a) over an evaluation zone according to at least a gaze direction is taken into account to implement the calculation.

8. The method according to claim 6, wherein the focalisation criterion is selected in the list consisting of optical power, astigmatism, high order aberration (HOA), strehl ratio, root means square (RMS), drop in acuity or contrast.

9. The method according to claim 1, wherein the personalized optical system characterizing a progressive addition spectacle lens wherein the front and the back surfaces may be progressive or regressive addition surfaces and wherein the geometrical factor Q=ADDF/ADD is a parameter used to meet the set of rules according to step c), ADDF being the addition of the front surface and ADD being the optical addition of the lens.

10. The method according to claim 1 wherein the personalized optical system characterises a progressive addition spectacle lens and wherein the “base curve” of the spectacle ophthalmic lens is a parameter used to meet the set of rules according to step c).

11. The method according to claim 1, wherein the personalized optical system characterises a progressive addition spectacle lens and wherein refractive index is a physical parameter used to meet the set of rules of step b) according to step c).

12. The method of claim 11, wherein the visual performance level of step a) is chosen in the sub-list of visual acuity performance, wherein an optical criterion of step b) is chosen within the visual field list consisting of object visual field in central vision, image visual field in central vision, object visual field in peripheral vision, image visual field in peripheral vision and another optical criterion of step b) is chosen within the magnification list consisting of magnification in central vision, magnification in peripheral vision, and wherein the rule linking the preceding visual performance level and the two preceding optical criteria is a trend relationship where the higher is the visual acuity performance level of the eye of the wearer, the higher is the value of the optical criterion chosen in the visual field list, and that respectively the lower is the visual acuity performance level of the eye of the wearer, the higher is the value of the optical criterion chosen in the magnification list.

13. A method for manufacturing a spectacle ophthalmic lens for a wearer, the method comprising the steps of: aa) providing the physical and geometrical parameters of a personalized optical system according to claim 1; bb) providing a lens substrate; and cc) manufacturing the spectacle ophthalmic lens according to the parameters of step aa).

14. A non-transitory computer program product comprising one or more stored sequence of instructions that is accessible to a processor and which, when executed by the processor, causes the processor to carry out the step c) of claim 1.

15. A non-transitory computer-readable medium storing one or more sequences of instructions of the non-transitory computer program product of claim 14.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic view of a lens plus eye system.

(2) FIG. 2 shows a ray tracing from the center of rotation of the eye.

(3) FIG. 3 shows a ray tracing from the center of the eye entrance pupil.

(4) FIG. 4 illustrates horizontal object visual field.

(5) FIGS. 5a and b illustrate addition of a surface.

(6) FIGS. 6 to 10 relate to a first embodiment according to the present invention.

(7) FIGS. 11 to 17 relate to a second embodiment according to the present invention.

(8) FIGS. 18 and 19 relate to a third embodiment according to the present invention.

(9) FIG. 20 shows an exemplary embodiment of a rule of step b) linking one visual performance level with one optical criterion, according to the present invention.

(10) FIG. 21 shows an exemplary embodiment of a rule of step b) linking one visual performance level with two optical criteria, according to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(11) Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve the understanding of the embodiments of the present invention. Same reference on different figures refers to the same object.

(12) FIG. 1 illustrates a schematic view of a lens-plus-eye system. The lens 10 has a front face 110 and a rear (or back) face 120. Referring to FIG. 1, an eye position can be defined by the center of rotation of the eye, CRE, and the entrance pupil central point P. PS is the pupil size (not drawn to scale). The distance q′ between the CRE and the lens 10 is generally, but not limited to, set to 25.5 mm, and p′ defines the position of the eye entrance pupil with respect to the CRE.

(13) FIG. 2 illustrates a model for central vision in the purpose of assessing a criterion in a central vision situation by ray tracing. In a central vision situation, the eye rotates about its center of rotation as well as the entrance pupil of the eye. A gaze direction is defined by two angles (α,β) measured with regard to reference axes R=(X,Y,Z) centered on the CRE. For assessing a central vision criterion in a gaze direction (α,β), a gaze ray 1 is built from the CRE in the gaze direction (α,β). 11 is the incident ray after passing through the lens 10.

(14) FIG. 3 illustrates a model for peripheral vision in the purpose of assessing a criterion in a peripheral vision situation through ray tracing. In a peripheral vision situation, a gaze direction (α,β) (not represented here) is fixed, and an object is viewed in a peripheral ray direction different from the gaze direction. A peripheral ray direction is defined by two angles (α′,β′) measured with regard to reference axes R′=(X′,Y′,Z′) centered on the eye entrance pupil and moving along the gaze direction axis given by the fixed direction (α,β) and represented by axis X′ on FIG. 3. For assessing a peripheral vision criterion in a peripheral ray direction (α′,β′), a peripheral ray 2 is built from the center of the pupil P in a peripheral ray direction (α′,β′). 12 is the emergent peripheral ray corresponding to the incident peripheral ray 10.

(15) According to the gaze ray 1 (in central vision) or to the peripheral ray 2 (in peripheral vision), the ray-tracing software computes the corresponding emergent ray, alternatively under reference 11 and 12 on FIGS. 2 and 3. Then, an object point is chosen on the ray in the object space and from this object a pencil of rays is built to calculate the final image. Ray tracing enables then to compute the selected criteria.

(16) FIG. 4 illustrates an example of visual field VF in central vision for two rays 41 and 51 issued from the CRE. The lens 10 is represented as a surface with isoastigmatism lines 101-106. Rays 41 and 51 are defined as the intersection between a predetermined horizontal axis given by a direction α and two predetermined isoastigmatism lines 101 and 104. These intersections enable to trace ray 41 along direction (α,β1) and ray 51 along direction (α,β2). The object visual field VF in central vision is a function of prismatic deviation and can be mathematically expressed for two rays as:
VF(α)=|β1+Dp_H(α,β1)|+|β2+Dp_H(α,β2)| Dp_H(α,β1) represents horizontal prismatic deviation in the gaze direction (α,β1). Horizontal prismatic deviation is the component of the prismatic deviation in a horizontal plane. Dp_H(α,β2) represents horizontal prismatic deviation in the gaze direction (α,β2).

(17) FIGS. 5a and b illustrate addition of respectively the front surface (for example reference 110 of FIG. 1) and of the back surface (120 of FIG. e1) of a progressive addition spectacle ophthalmic lens, where the variation of the sphere value Sph (in diopter) (respectively 210, 220) is represented according to the Y axis.

(18) Zones 211, 221 regard the far vision zones, zones 213, 223 regard the near vision zones and zones 212, 222 regard the intermediate vision zone. Addition, ADD.sub.F, respectively ADD.sub.B, refer to the sphere value difference between the near vision zone and the far vision zone when considering the front surface and respectively to the sphere value difference between the far vision zone and the near vision zone when considering the back surface.

(19) According to the examples of FIGS. 5a and 5b both front and back surfaces are progressive surfaces and the resulting addition of a lens having said both surfaces would be about ADD=ADD.sub.F+ADD.sub.B.

(20) According to the present invention a parameter Q is defined where Q=ADD.sub.F/ADD.

(21) FIGS. 6 to 10 relate to a first example of an embodiment of the method according to the present invention.

(22) According to this example, the visual performance level of step a) of the method of the invention is the central visual acuity measured according to binocular vision and two optical criteria of step b) of the method of the invention are chosen directed to object visual field in central vision and to magnification in central vision.

(23) According to said example, the object visual field in central vision is considered in the near vision zone.

(24) FIGS. 6 and 7 show how said parameter is evaluated; the field to be considered refers to a field which incorporates rays passing through the CRE in directions defined for a given a value and for a β range Δβ.

(25) α is chosen so as the rays passing through the CRE meet the near vision zone. For said example, α=−34°, and Δβ=20° for a central β value of 6° (thus β ranges from −4° to +16°).

(26) The vision field situated between the CRE and lens 10 is the near vision image vision field (NV-IVF), equal to Δβ and the vision field seen after passing through lens 10 is the near vision object vision field (NV-OVF).

(27) For the purpose of the demonstration, one chooses a lens 10 which fits a prescription where the prescribed dioptric power in far vision is −3 diopters, the prescribed astigmatism is 0 in far vision and the addition is +2 diopters.

(28) One further considers the case where Q, the ratio of the repartition of the addition between the front and the back surfaces, is a parameter used to meet a set of rules of step b) according to step c) of the method of the invention.

(29) A plurality of ophthalmic lens optical systems has been evaluated and results are reported on FIGS. 8 to 10 where:

(30) In FIG. 8, curve 80 corresponds to the variation of NV-OVF as a function of Q for NV-IVF constant;

(31) In FIG. 9, curve 90 corresponds to the variation of the near vision magnification, NV-M, as a function of Q.

(32) In FIG. 10, curve 100 corresponds to Q variation as a function of central visual acuity measured according to binocular vision.

(33) Values presented in those figures relate to optical system characteristics that have been calculated by computer means thanks to an optimization method wherein at least a focalisation criterion over an evaluation zone according to at least a gaze direction is taken into account to implement the calculation.

(34) The calculated optical systems of the example have been obtained thanks to following steps: performance definitions of optical system targets where, for each gaze direction within a 40° vision cone, performances are defined regarding focalisation criteria consisting of optical power and astigmatism (meaning that for each gaze direction an optical power and an astigmatism values are attributed); optimization where the generated optical systems have a variable addition between the front and the back faces (Q variation), but are calculated so as the optical performances are substantially the same regarding optical power and astigmatism values; therefore in each gaze direction the calculation is done so that the tolerance regarding optical power value is equal or less than 0.05 diopters and regarding the astigmatism value is equal or less than 0.1 diopters; according to said calculations, the optical power and astigmatism values of the different optical systems are substantially the same, but criteria regarding visual field and magnification may vary from an optical system to another one.

(35) Results of said calculations are presented on FIGS. 8 to 10.

(36) FIG. 8 shows the variation of the calculated near vision object visual field (NV-OVF, in degrees) according to the Q factor.

(37) FIG. 9 shows the variation of the calculated near vision magnification according to the Q factor.

(38) Said curves demonstrate that NV-OVF and NV-M vary according to opposite trends as a function of the Q factor.

(39) FIGS. 8 and 9 demonstrate that one can offer ophthalmic spectacle lens optical systems where the optical performance regarding optical power and astigmatism values are substantially the same, but where visual field and magnification may significantly vary.

(40) Thanks to variation of visual field and magnification for given optical power and astigmatism values, one can provide optical system suitable to meet the needs of a specific wearer.

(41) Said needs can be linked to a visual performance level of the wearer.

(42) Therefore and according to the present invention, one proposes to improve the visual comfort of the wearer thanks to increasing the magnification value (near vision magnification according to the present example) when the wearer's acuity is low so that the wearer can more easily take into account object image details; one also proposes to improve the visual comfort of the wearer thanks to enlarging his vision field (near vision object visual field according to the present example) when the wearer's acuity is high so that the wearer can more easily scan his environment.

(43) According to the present example, said balance between vision field and magnification can be obtained thanks to varying the repartition of the addition between the front and the back surface (Q factor). Thus the Q factor can be chosen as a parameter used to meet the set of rules of step b) according to step c) of the process according to the invention.

(44) An example of a said rule is illustrated in FIG. 10 where the chosen Q factor (ordinate) is determined as a function of the maximal corrected central vision acuity measured according to binocular vision (abscissa).

(45) For wearers which acuity is low (equal or less than 8/10), one suggests to choose a Q factor equal to 2, meaning that, according to FIGS. 8 and 9, a high NV-M value is preferred and according to the present example NV-OVF=21.6° and NV-M=0.95.

(46) For wearers whose acuity is high (equal or more than 14/10), one suggests to choose a Q factor equal to −2 meaning that a high NV-OVF value is preferred, and according to the present example NV-OVF=22.10° and NV-M=0.91.

(47) For wearers whose acuity is medium, one suggests to find a compromise between the two said optical parameters where the Q factor varies linearly between the two preceding values. Thus and according to the present example, one choose Q=−1 for an intermediate acuity equal to 12.5/10 thus NV-OVF=22.0° and NV-M=0.92. According to a second example of the method according to the present invention, one aims to obtain optimized optical systems when considering both far vision and near vision.

(48) Evaluation zones are defined according to FIGS. 11 and 12, both for far vision and near vision zones. According to the present example Δβ.sub.NV=Δβ.sub.FV=20° centered around β=6° for β.sub.NV and centered around β=0° for β.sub.FV.

(49) α values are following: α.sub.NV=34° and α.sub.FV=−8°.

(50) Optimisation process is implemented according to the rules described regarding the preceding example.

(51) For the present example the prescription of the wearer is sphere −3 in far vision, the astigmatism is 0 in far vision and the addition is 2.

(52) FIGS. 13 and 14 show the variation of respectively magnification parameters and object visual field parameters according to the Q factor and to the base curve B of the optical system.

(53) FIG. 13 shows calculated curves regarding magnification parameters as referred in table 1 where the number of the curve is defined according to the base curve B and to the vision zone.

(54) TABLE-US-00001 TABLE 1 Base curve B Near vision NV-M Far vision FV-M (in diopter) (number of the curve) (number of the curve) 1.75 136 135 2.75 132 131 3.75 134 133

(55) FIG. 14 shows calculated curves regarding vision field parameters referred in table 2 where the number of the curve is defined according to the base curve B and to the vision zone.

(56) TABLE-US-00002 TABLE 2 Base curve β Far vision FV-OVF Near vision NV-OVF (in diopter) (number of the curve) (number of the curve) 1.75 145 146 2.75 141 142 3.75 143 144

(57) FIG. 13 teaches that far vision or near vision magnification (respectively FV-M and NV-M) vary according to different trends when considering the Q factor and the base curve value.

(58) FV-M and NV-M increase when the base curve value increases, for a constant Q factor value.

(59) The FV-M(Q) curves are almost parallel one to another when the base curve value varies.

(60) Same applies for NV-M(Q).

(61) NV-M values increase, for a same base curve value when the Q factor increases, where FV-M values are almost constant, for a same base curve value, as a function of the Q factor.

(62) FIG. 14 teaches that far vision or near vision object visual field (respectively FV-OVF and NV-OVF) vary according to different trends when considering the Q factor and the base curve value.

(63) FV-OVF and NV-OVF decrease when the base curve value increases, for a constant Q factor value.

(64) The FV-OVF (Q) curves are almost parallel one to another when the base curve value varies.

(65) Same applies for NV-OVF(Q).

(66) NV-OVF values decreases, for a same base curve value when the Q factor increases, where FV-OVF values are almost constant for a same base curve value, as a function of the Q factor.

(67) Thanks to said curves, one can offer to a wearer an optimized optical system when choosing an adapted base curve value and Q factor value according to his visual acuity.

(68) One can make the assumption that the global visual perception of a wearer which visual acuity is more than 14/10 is only limited by object visual field. For such wearers, an optimized solution would be offering an optical system where object visual fields are the largest, both for near and far visions. Thanks to the teachings of FIGS. 13 and 14, one will choose an optical system where the base curve value is 1.75 and the Q factor is −2.

(69) On the opposite side, one can make the assumption that the global visual perception of a wearer which visual acuity is less than 8/10 is only limited by magnification. For such wearers, an optimized solution would be offering an optical system where magnification is the largest, both for near and far vision.

(70) Thanks to the teaching of FIGS. 13 and 14, one will choose an optical system where the base curve is 3.75 and the Q factor is 2.

(71) For wearers which visual acuity is between 8/10 and 14/10, one will suggest different routes taking into account the here above mentioned parameters.

(72) According to an embodiment, one defines two weighting factors, one directed to magnification F.sub.M and the other one directed to object visual field F.sub.OVF. Each weighing factor, F, varies between 0 and 1.

(73) When considering a range of magnification or object visual field values calculated according to different parameters, such as the base curve value and/or the Q factor value, one will choose an optical system where:
M=M.sub.min+(M.sub.max−M.sub.min)×F.sub.M and
OVF=OVF.sub.min+(OVF.sub.max−OVF.sub.min)×F.sub.OVF

(74) where “max” refers to the highest value calculated for magnification, respectively object visual field when varying the parameter(s) within a chosen range and “min” refers to corresponding lowest value.

(75) For wearers which visual acuity is equal or less than 8/10, one will define F.sub.M=1 and F.sub.OVF=0.

(76) For wearers which visual acuity is equal or more than 14/10, one will define F.sub.M=0 and F.sub.OVF=1

(77) Between said two cases, one will choose a F factor according to FIG. 15 where the abscissa relates to visual acuity and ordinate to the weighing factor F.

(78) Curve 151 represents the variation of F.sub.OVF and curve 152 represents the variation of F.sub.M, according to visual acuity.

(79) Dotted lines regard an example where the wearer's visual acuity is 12. Thanks to FIG. 15 one determines F.sub.M=0.33 and F.sub.OVF=0.67.

(80) Following values are then determined:

(81) FV-M=0.86

(82) NV-M=0.94

(83) FV-OVF=22.63°

(84) NV-OVF=21.71°

(85) Results are reported on the data of FIGS. 13 and 14 as shown on FIGS. 16 and 17, where one can determine that the best optical system for said wearer relates to a base curve value of 2.75 and a Q factor equal to 1.

(86) FIG. 20 shows an exemplary embodiment of a rule of step b) linking a subjective estimation of the total field of view by a wearer (visual performance level) with the field of view (optical criterion) according to the present invention.

(87) FIG. 21 shows an exemplary embodiment of a rule of step b) linking a visual acuity (A) of a wearer with NV-OVF and NV-M, according to the present invention.

(88) This rule is for example set from the graph shown in FIG. 15.

(89) FIGS. 18 and 19 relate to a third example of an embodiment according to the present invention where one aims to offer another approach to the problem addressed according to the first example according to the invention. Then, according to said third example, object visual field in central vision is considered in the near vision zone (as illustrated on FIGS. 6 and 7).

(90) According to said example, one let geometrical parameters of the optical system vary so as to let the Q factor value vary according to visual acuity. Constraints regarding optical power and astigmatism are released to let the optimization according to magnification and object visual field be more efficient.

(91) According to following example, a plurality of wearers have the same prescription, where the prescribed dioptric power in far vision is −3 diopters, the prescribed astigmatism is 0 diopter in far vision, and the addition is 2.

(92) Different optical systems have been evaluated where the Q factor is taken into account according to following steps: optical system target performances are defined where, for each gaze direction within a vision cone of 40°, performances are specified for optical power and for astigmatism; optimization is implemented wherein all the generated optical systems have different addition repartition between front and back surfaces (i.e. different Q factor values); optimization is made in each gaze direction so as the tolerance regarding optical power value is equal or less than 0.3 and regarding the astigmatism value is equal or less to 0.3 (said tolerance values were respectively 0.05 and 0.1 according to the first example).

(93) Other steps are similar to those of the first example.

(94) One will then generate a plurality of optical systems which are in the vicinity of those according to the first example but differ because the weight on focalisation criteria (optical power and astigmatism) compared to the weight of optical criteria (object vision field and/or magnification) is lowered in the present example compared to the first example.

(95) Table 3 reports data used to calculate two examples of optical system and corresponding results according to the first example and the third example of embodiments according to the present invention. The optical system is referred as (x, y) where x corresponds to an optical system example and y corresponds to associated Q factor (which is equal to 2 or −2 according to the present optical system examples).

(96) TABLE-US-00003 TABLE 3 Example of Optical Optical power Astigmatism NV-M NV-OVF embodiment system Target Final value Target Final value final final (°) 1 (1, 2) −0.7 ± 0.05 −0.68 0 ± 0.1 0.06 0.948 21.59 1   (2, −2) −0.7 ± 0.05 −0.74 0 ± 0.1 0.1 0.908 22.10 3 (1, 2) −0.7 ± 0.3  −0.83 0 ± 0.3 0.24 0.941 21.76 3   (2, −2) −0.7 ± 0.3  −0.97 0 ± 0.3 0.26 0.891 22.23

(97) FIGS. 18 and 19 show the results according to the first example of an embodiment (results of FIGS. 8 and 9 are reported) compared to those of the present third example of an embodiment of the invention, where near vision object visual field results as a function of the Q factor are reported on FIG. 18 and results of near vision magnification as a function of the Q factor is reported on FIG. 19.

(98) Thanks to releasing tolerances regarding the optical power value and the astigmatism value, one can offer largest object visual fields or highest M for the wearer for the same Q factor value compared to the first example of an embodiment.

(99) One can than offer to a wearer an optimized optical system based on the set of optical systems determined according to said third example of an embodiment and where the selection is made according to the former teaching of the first example of an embodiment of the present invention.

(100) It is clear that it is possible to employ other methods of optimization, and other ways of representing surfaces differing from the method proposed.

(101) The invention has been described above with the aid of embodiments without limitation of the general inventive concept. In particular the present invention provides a method for calculating by optimization an optical system, the optical system being all kinds of optical lenses, particularly ophthalmic lenses, e.g. single vision (spherical, torical), bi-focal, progressive, aspherical lenses (etc.).