Title of Invention	METHODS FOR PRODUCING PROGRESSIVE ADDITION LENSES
Abstract	A PROCESS FOR PRODUCING A PROGRESSIVE ADDITION LENS FOR A LENS WEARER COMPRISING THE STEPS OF : A) PROVIDING AN OPTICAL PERFORM COMPRISING AT LEAST ONE SURFACE HAVING A PREDETERMINED FIRST CYLINDER AXIS, A PREDETERMINED CYLINDER POWER SUCH AS 0.125 TO 6.00 DIOPTERS AND A PREDETERMINED FIRST NEAR VISION ZONE POSITION; B) PROVIDING A MOLD FOR CASTING A SURFACE ONTO THE OPTICAL PERFORM, THE MOLD COMPRISING A SECOND NEAR VISION ZONE THAT IS ALIGNED WITH THE LENS WEARER'S NEAR VIEWING PUPIL LOCATION; AND C) POSITIONING THE PERFORM IN RELATION TO THE MOLD IN ORDER TO PROVIDE THE RESULTING LENS WITH A CYLINDER AXIS DESIRED FOR THE LENS WEARER.

Title of Invention

METHODS FOR PRODUCING PROGRESSIVE ADDITION LENSES

Abstract

A PROCESS FOR PRODUCING A PROGRESSIVE ADDITION LENS FOR A LENS WEARER COMPRISING THE STEPS OF : A) PROVIDING AN OPTICAL PERFORM COMPRISING AT LEAST ONE SURFACE HAVING A PREDETERMINED FIRST CYLINDER AXIS, A PREDETERMINED CYLINDER POWER SUCH AS 0.125 TO 6.00 DIOPTERS AND A PREDETERMINED FIRST NEAR VISION ZONE POSITION; B) PROVIDING A MOLD FOR CASTING A SURFACE ONTO THE OPTICAL PERFORM, THE MOLD COMPRISING A SECOND NEAR VISION ZONE THAT IS ALIGNED WITH THE LENS WEARER'S NEAR VIEWING PUPIL LOCATION; AND C) POSITIONING THE PERFORM IN RELATION TO THE MOLD IN ORDER TO PROVIDE THE RESULTING LENS WITH A CYLINDER AXIS DESIRED FOR THE LENS WEARER.

Full Text	METHODS FOR PRODUCING PROGRESSIVE ADDITION LENSES Field of the Invention The present invention relates to multifocal ophthalmic lenses. In particular, the invention provides progressive addition lenses in which unwanted legs astigmatism is reduced without functional compromise of the distance and channel widths through the intermediate and near vision zones, as compared to conventional progressive addition lenses. Background of the Invention The use of ophthalmic lenses for the correction of ametropia is well known. For example, multifocal lenses, such as progressive addition lenses ("PAL"s"), are used for the treatment of presbyopia. The surface of a PAL provides far, intermediate, and near vision in a gradual, continuous progression of vertically increasing dioptric power from far to near focus, or top to bottom of the lens. PAL"s are appealing to the wearer because PAL"s are free of the visible ledges between the zones of differing dioptric power that are found in other multifocal lenses, such as bifocals and trifocals. However, an inherent disadvantage in PAL"s is unwanted lens astigmatism, or astigmatism introduced or caused by one or more of the lens" surfaces. Generally, the unwanted lens astigmatism is located on either side of the near vision zone of the lens and, at or near its approximate center, reaches a maximum level that corresponds approximately to the near vision dioptric add power of the lens. Generally, a PAL with a 2.00 diopter add power and 15 mm channel length will have about a 2.00 diopter maximum, localized unwanted astigmatism. The channel width of the lens will be approximately 6 mm in which the unwanted astigmatism is less than or equal to a 0.75 diopter threshold value. Any number of lens designs have been tried in attempting to either or both reduce unwanted astigmatism or increase the minimum channel width. However, current state-of-the-art progressive addition lenses provide only minimal decreases in unwanted astigmatism while having large areas in the lenses" peripheries that are unusable due to unwanted astigmatism. Thus, a need exists for a PAL that reduces maximum, localized unwanted astigmatism and, at the same time, provides an increase in the minimum channel width. Brief Description of the accompanying Drawings FIG. la is a side view of a lens of the invention. FIG. lb is an astigmatism map of the lens of FIG. 1a FIG. 2a is a side view of a lens of the invention. FIG. 2b is an astigmatism map of the lens of FIG. 2a. FIG. 3 is a side view of a lens of the invention. FIG. 4a is a side view of the lens of the invention. FIG. 4b is an astigmatism map of the lens of FIG. 4a FIG. 5 a is a side view of a lens of the invention. FIG. 5b is an astigmatism map of a progressive surface of the lens of FIG. 5a. FIG. 5c is an astigmatism map of a progressive surface of the lens of FIG. 5a. FIG. 5d is an astigmatism map of the lens of FIG. 5a. Description of the Invention and its Preferred Embodiments The present invention provides progressive addition lenses, as well as methods for their design and production, in which the maximum, localized unwanted astigmatism that is associated with a given dioptric add power is reduced compared to prior art lenses. Additionally, the distance width, or width about the optical center of the lens that is free of about 0.50 diopters or more of unwanted astigmatism, and minimum channel width of the lens is suitable for use by the lens wearer. For purposes of the invention, by "channel" is meant the corridor of vision that is free of astigmatism of about 0.75 diopters or greater when the wearer"s eye is scanning from the distance zone to the near zone and back. By "lens" or "lenses" is meant any ophthalmic lens including, without limitation, spectacle lenses, contact lenses, intraocular lenses and the like. Preferably, the lens of the invention is a spectacle lens. It is one discovery of the invention that maximum, localized astigmatism may be reduced by combining two or more progressive addition surfaces each providing a dioptric add power that combines with that of the other surface or surfaces to produce a lens of a higher dioptric add power than that of the surfaces individually. By "dioptric add power" is meant the amount of dioptric power difference between the near and far vision zones of a progressive addition surface. The lens of the invention exhibits less maximum, localized unwanted astigmatism and a wider channel than would be expected by producing a lens with the same dioptric add power using only a single progressive addition surface. Further, it is a discovery of the invention that the use of more than one progressive addition surface ensures that the distance dioptric power and the total dioptric add power needed to correct the wearer"s vision are uncompromised. It is yet another discovery of the invention that when the progressive surfaces" dioptric add power areas are misaligned with respect to one another, the resultant total maximum, localized unwanted astigmatism of the lens is less than the sum of the maximum, localized unwanted astigmatism contributed by the individual dioptric add powers of each progressive addition surface. By "progressive addition surface" is meant a continuous, aspheric surface having far and near vision zones and a zone of increasing dioptric power connecting the far and near vision zones. By "maximum, localized unwanted astigmatism" is meant the highest, measurable level of astigmatism in an area of unwanted astigmatism on a lens surface. In one embodiment, the lens of the invention comprises, consists essentially of, and consists of: a.) a first progressive addition surface having one or more areas of maximum, localized unwanted astigmatism and a first dioptric add power; and b.) a second progressive addition surface having one or more areas of maximum, localized unwanted astigmatism and a second dioptric add power, the progressive addition surfaces disposed in relation to each other so that a portion or all of the areas of maximum, localized unwanted astigmatism are misaligned and wherein the dioptric add power of the lens is the sum of the first and second dioptric add powers. In another embodiment, the invention provides a process for producing a lens comprising, consisting essentially of, and consisting of the steps of: a.) providing at least a first and a second progressive addition surface, the first progressive addition surface having one or more areas of maximum, localized unwanted astigmatism and a first dioptric add power and the second progressive addition surface having one or more areas of maximum, localized unwanted astigmatism and a second dioptric add power; and b.) disposing the first and second progressive addition surfaces so that a portion or all of the areas of maximum, localized unwanted astigmatism are misaligned and the dioptric add power of the lens is the sum of the first and second dioptric add powers. By "misaligned" is meant that the surfaces, and thus the areas of unwanted astigmatism, are arranged or disposed in relation to one another so that a portion or all of the areas of maximum, localized unwanted astigmatism of one surface do not substantially coincide with one or more areas of maximum, localized unwanted astigmatism of the other surface. Preferably, the misalignment is such that no area of maximum, localized unwanted astigmatism of a surface substantially coincides with that of the other surface. The progressive addition surfaces used in the lens of the invention may be misaligned by any of a number of methods. For example, the optical centers of the surfaces may be shifted either or both laterally or vertically with respect to each other. By "optical center" is meant the point on a surface intersected by the optical axis of the lens. One ordinarily skilled in the art will recognize that, if the optical centers are shifted laterally, the minimum channel width is reduced by the extent of the shift. Thus, a progressive addition lens design using a lateral shift preferably uses progressive addition surfaces with wider channel widths to compensate for the diminution in channel width caused by the shift. Alternatively, if the optical centers of the surfaces are shifted vertically, the channel length will be increased. By "channel length is meant the distance along the central meridian of the surface between the optical center and the top end of the near vision zone. Thus, a design using such a shift preferably uses progressive addition surfaces with shorter channel lengths in compensation. As yet another alternative, maintaining the optical centers of the progressive surfaces coincident with each other, the centers may be rotated with respect to one another. In a preferred embodiment, each surface is designed so that it is asymmetric about the center line of its channel. In this case, the areas of maximum, localized unwanted astigmatism of the surfaces do not substantially coincide on rotation of the optics about an axis joining the surfaces" optical centers. By "asymmetric" is meant that the power and astigmatism maps of the surface are asymmetric about the center meridian of the surface. The lateral and vertical shifts are done in such a way as to preserve the distance and near vision dioptric powers of the lens. In order to minimize the introduction of lens prism power, the shifts must occur so that the optical center of one progressive addition surface is shifted along a curve that is parallel to the distance curve of the other progressive addition surface. In the case of rotations, the surfaces are rotated about their optical centers so that the distance and near powers are substantially unaffected. One ordinarily skilled in the art will recognize that the rotational misalignment may be in addition to the misalignment carried out for purposes of reducing unwanted astigmatism. The amount of misalignment, or the vertical shift, lateral shift or rotation of optical centers, is an amount sufficient to prevent substantial superposition, or coincidence, of the maximum, localized unwanted astigmatism areas of the progressive addition surfaces. More specifically, it is believed that the misalignment leads to a mismatch of the direction of the astigmatic vectors associated with one surface relative to the corresponding astigmatic vectors of the other surface resulting in the total maximum, localized unwanted astigmatism for the final lens being less than that if the vectors were aligned. The lateral or vertical shift may be about 0.1 mm to about 10 mm, preferably about 1.0 mm to about 8 mm, more preferably about 2.0 mm to about 4.0 mm. Rotational shifts may be about 1 to about 40 degrees, preferably about 5 to about 30 degrees, more preferably about 10 to about 20 degrees. As yet another alternative for misalignment, each surface may be designed so that the channel length of the surfaces are of different lengths. In this embodiment, the areas of maximum, localized, unwanted astigmatism of the surfaces do not align when the optical centers of the surfaces are brought into alignment. As a result, the unwanted astigmatism is reduced compared to a lens of the same total dioptric add power. The greater the difference between the channel lengths, the greater will be the reduction in maximum, localized unwanted astigmatism. However, the channel lengths must not be so large as to produce a mismatch in the near vision zones so that the near vision of the lens wearer is compromised. The lens resulting from this embodiment will have a channel length falling between that of each surface and dependent upon the dioptric add power contributed by each surface to the total dioptric add power of the lens. The channel length difference between the surfaces may be about 0.1 mm to about 10 mm, preferably about 1 mm to about 7 mm, more preferably about 2 mm to about 5 mm. The progressive addition surfaces may each be independently on the convex or concave surface of the lens or in a layer between the outer concave and outer convex surfaces of the lens. Other surfaces, such as spheric and toric surfaces, designed to adapt the lens to the ophthalmic prescription of the lens" wearer may be used in combination with, or in addition to, one or more of the progressive addition surfaces. For example, one of the progressive addition surfaces, preferably a concave surface, may be combined with a toric surface to provide a toric progressive surface having a dioptric add power and a cylinder power at a particular axis. In the case of a concave, toric progressive surface, the convex surface preferably is a non-toric surface. In order to both provide the desired dioptric add power and correct for the lens wearer"s astigmatism, each of the surfaces" near vision zones may be aligned with the wearer"s pupil location during near viewing and the cylinder axis of the toric progressive surface placed so as to correspond to the wearer"s prescription. However, this method necessitates that a toric progressive surface be provided at each of the possible 180 degree cylinder axes orientations to provide a full prescriptive range of lenses. It is yet another discovery of this invention that the dioptric add power decreases slowly moving horizontally away from the center of the near vision zone to the surface"s periphery. Given this fact, a rotational misalignment of the surfaces" near vision zones of about + or - about 1 to about 25, preferably + or - about 1 to about 15, more preferably + or - about 1 to about 13 degrees may be used while achieving the desired lens dioptric add power. This discovery permits limiting the number of cylinder axis and near vision zone positions used so that a toric progressive surface need not be provided at each cylinder axis degree. More specifically, a preferred process for producing a lens with a toric progressive surface is as follows. An optical preform is selected, the preform having a concave surface with a predetermined cylinder power, predetermined cylinder axis, and predetermined near vision zone location. By "optical preform" or "preform" is meant a shaped, optically transparent article capable of refracting light and possessing a convex and a concave surface, which article is suitable for use in producing a spectacle lens. The cylinder power preferably is the power required by the lens wearer. The predetermined cylinder axis may be any cylinder axis, but preferably is within a set number of degrees of the lens wearer"s required cylinder axis. The preform cylinder axis may be within about 0 to about 25 degrees, preferably about 0 to about 20 degrees, more preferably about 0 about 11 degrees of the required cylinder axis desired for the lens" wearer. Preferably, the cylinder axis orientation selected is one of a group of orientations that is less than the 180 possible orientations, more preferably the axis being one of a group of about 20 orientations, most preferably the orientation is +11.25, +33.75, + 56.25, +78.75, + 101.25, +123.75, +146.25, and +168.75 degrees relative to the three o"clock position on the preform. The preform"s concave surface near vision zone may be provided at any convenient position, but preferably is located so that its center is along the 270 degree axis of the preform. In a more preferred embodiment, preform cylinder axes are provided at+11.25, +33.75, + 56.25, +78.75, + 101.25, +123.75, +146.25, or +168.75 degrees relative to the three o"clock position on the preform and the near vision zone center is located along the 270 degree axis, the six o"clock position. A convex surface is provided for the lens by using a mold suitable for casting the surface onto the preform. Preferably, the mold is suitable for the casting of a progressive surface. The mold near vision zone may be provided at any convenient position but preferably is at a position that is aligned with the near viewing pupil position of the lens wearer. Typically, this position will be on either side of the 270 degree axis, the 6 o"clock position, of the mold depending on whether the left or right lens is being fabricated. Preferably, the position is within about 0 to about 20, more preferably about 5 to about 15, most preferably about 8 to about 10 degrees on either side of the 270 degree axis. The selected preform is positioned, or rotated, in relation to the mold selected so that the cylinder axis of the resulting lens will be that required by the lens wearer. For example, if the lens wearer"s required cylinder axis is 180 degrees for the left eye and the optical preform cylinder power is at the 11.25 degree axis, with the near vision zone at 270 degrees, the preform is rotated so that its cylinder axis falls along the mold"s 180 degree axis. This aligns the cylinder axis of the preform to the wearer"s required cylinder axis. It will be recognized that the rotation of the preform in relation to the mold also produces a rotational misalignment of the preform and mold near vision zones. However, this rotational misalignment is tolerable up to about + or - 25 degrees for purposes of achieving the desired lens dioptric add power. Thus, in yet another embodiment, the invention provides a process for producing a progressive addition lens for a lens wearer, and lenses produced by the process, comprising, consisting essentially of and consisting of: a.) providing an optical preform comprising at least one surface having a predetermined first cylinder axis, a predetermined cylinder power, and a predetermined first near vision zone position; b.) providing a mold for casting a surface onto the optical preform, the mold comprising a second near vision zone position that is aligned with the lens wearer"s near viewing pupil location; and c.) positioning the preform in relation to the mold in order to provide the resulting lens with a cylinder axis desired for the lens wearer. In an alternative embodiment of the process, an optical preform is provided with at least one surface, preferably the convex surface, having a near vision zone, preferably a progressive addition surface. The near vision zone of this surface is aligned with the lens wearer"s near viewing pupil location. A mold suitable for casting a toric surface onto the preform is used, the mold having a predetermined cylinder axis, cylinder power, and near vision zone location as above-described. Thus, in an alternative embodiment, a process is provided for producing a progressive addition lens for a lens wearer, and lenses produced by the process, comprising, consisting essentially of and consisting of: a.) providing an optical preform comprising at least one surface having a first near vision zone position that is aligned with the lens wearer"s near viewing pupil location; b.) providing a mold for casting a surface onto the optical preform, the mold comprising a predetermined first cylinder axis, predetermined a cylinder power, and a predetermined second near vision zone position; and c.) positioning the preform in relation to the mold in order to provide the resulting lens with a cylinder axis desired for the lens wearer. One ordinarily skilled in the art will recognize that any number of a wide variety of predetermined cylinder axes and near vision zone placements may be used. However, it is preferred that the predetermined cylinder axes and near vision zone placements be selected from those shown on Table 1 for the listed lens cylinder axis prescription requirements. For the lenses and processes of the invention, the dioptric add power of each of the progressive addition surfaces used in the invention is selected so that the sum of their dioptric add powers is substantially equal to the value needed to correct the lens wearer"s near vision acuity. Additionally, the dioptric add power of each surface is selected in view of the maximum, localized unwanted astigmatism associated with a given near dioptric power. The dioptric add power of the progressive addition surfaces may be each independently from about + 0.01 diopters to about +3.00 diopters, preferably from about +0.25 diopters to about +2.00 diopters, more preferably about +0.50 to about +1.50 diopters. Similarly, the distance and near dioptric powers for each surface are selected so that the sum of the powers is the value needed to correct the wearer"s distance and near vision. Generally, the distance dioptric power for each surface will be within the range of about 0.25 diopters to about 8.50 diopters. Preferably, the dioptric power of the distance zone of the concave surface may be + or - about 2.00 to about 5.50 diopters and for the convex surface, + or - about 0.5 to about 8.00 diopters. The near vision dioptric power for each of the surfaces will be about 1.00 diopters to about 12.00 diopters. In those embodiments in which a cylinder power is used, the cylinder power may be about -0.125 to about -6.00 diopters, preferably about -0.25 to about -3.00 diopters. The progressive addition surfaces and lenses of the invention may be formed by any convenient method such as, without limitation, thermoforming, molding, grinding, casting or the like. In a preferred method, an optical preform having a progressive addition surface is used and a second progressive addition surface is cast onto the preform. In a more preferred method, a preform the concave surface of which is a progressive addition surface with a base spherical power and a cylinder power is used and a progressive addition surface is formed on the front surface by any convenient method, preferably by casting and more preferably by surface casting. The invention will be clarified further by a consideration of the following, non-limiting examples. Examples Example 1 Referring to FIG. la, lens 10 of the invention is shown having convex progressive addition surface 11 and concave progressive addition surface 12. Surface 11 has distance zone 13 with a curvature of 6.00 diopters and near zone 18 with a curvature of 7.00 diopters. Surface 12 has distance zone 19 with a curvature of 6.00 diopters and near zone 21 with a curvature of 5.00 diopters. The resulting distance power of the lens is 0.00 diopters and the dioptric add power of the lens is 2.00 diopters, 1.00 diopters contributed by each of surfaces 11 and 12. As shown in FIG. la, the convex and concave optical centers 16 and 17, respectively, are shifted with respect to each other by 4.0 mm. FIG. lb is an astigmatism map of lens 10 illustrating the misalignment of the surfaces. Areas 22 and 23 are of the unwanted astigmatism for surfaces 11 and 12, respectively. The locations of the maximum, localized astigmatism 14 and 15 do not overlap and, thus, are not additive. The maximum, localized unwanted astigmatism value of 1.90 D for this lens is shown in Table 1 and is significantly lower than the 2.20 D that is found in a conventional PAL of the same near dioptric power. Example 2 A lens with two progressive addition surfaces is used, the misalignment for which is 8.00 mm. The misalignment results in a reduction of maximum localized u unwanted astigmatism of 0.30 D compared to the prior art Lens of Table 1. Example 3 As shown in FIGs. 2a and 2b, lens 20 with a concave progressive addition surface 25 is seen. Surface 25 has distance and near zone curvatures of 6.00 and 5.00 diopters, respectively. Convex surface 24 with distance and near zone curvatures of 6.00 and 7.00 diopters is also shown. The optical center 27 of surface 25 is rotated by a, an amount of 10 degrees, with respect to that of optical center 26 of convex progressive surface 24. In FIG. 2b, the astigmatism map of lens 20 is shown. Areas 31 and 32 depict the areas of unwanted astigmatism for surfaces 24 and 25, respectively. Maximum, localized unwanted astigmatism areas 28 and 29 for surfaces 24 and 25, respectively, are also shown. Table 2 shows that the resulting lens has a maximum, localized unwanted astigmatism of 1.90 diopters as compared to 2.10 diopters for a prior art lens. Examples 4-6 The concave progressive addition surface of a lens is rotated around its optical center by 20, 30, and 40 degrees with respect to the convex progressive addition surface. The rotations result in maximum, localized unwanted astigmatisms of 1.85, 1.75, and 1.41 diopters, respectively as listed on Table 2. Example 7 FIG. 3 depicts a concave progressive addition surface 34 placed between surfaces 33 and 35 of lens 30. Lens 30 is made of an optical preform 38 having a refractive index of 1.60 and a cast layer 39 having a refractive index of 1.50. Convex surface 33 of preform 38 has optical center 36, a distance curvature of 6.50 diopters and a near curvature of 8.50 diopters. Concave surface 34 of preform 38 has optical center 37, a distance curvature ("DC") of 6.50 diopters and a near curvature ("NC") of 0.50 diopters derived by the formula: wherein n1 is the refractive index of optical preform 38 and n2 is the refractive index of layer 39. Optical center 37 is shifted vertically downwards 4 mm with respect to optical center 36. Concave surface 35 of layer 39 includes a cylindrical power of -2.00 D for correcting the wearer"s astigmatism. Lens 30 has a distance power of 0.00 diopters, a total dioptric add power of 3.00 diopters, arrived at by the 2.00 diopter dioptric add power of surface 33 and the 1.00 diopters dioptric add power of surface 34 combined. The maximum, localized unwanted astigmatism is lower than that of a conventional lens with a 3.00 diopters dioptric add power. Example 8 In FIG. 4a is depicted lens 50 having convex surface 51 and concave surface 52. Surface 51 is a progressive addition surface with optical center 53. Surface 52 is a combination progressive addition-toric surface having optical center 54 shifted vertically downwards 4 mm with respect to optical center 53. FIG. 4b depicts the astigmatism map for lens 50 showing the shift. Areas 55 and 56 are the areas of unwanted astigmatism, 57 and 58 being their respective maximum, localized unwanted astigmatism areas respectively, for surfaces 51 and 52. I-I is the toric axis for surface 52. The overlap of the progressive addition surfaces are such that, although the near and distance vision zones are preserved, the location of the maximum, localized unwanted astigmatisms 57 and 58 of each surface do not coincide and, thus, their effect is not additive. Example 9 Lens 60 is depicted in FIG. 5a in which a left oriented, convex progressive addition surface 61 shown combined with a right oriented, concave progressive addition surface 62. Each surface is depicted individually in FIGs. 5b and 5c, respectively. Optical centers 63 and 64 of each surface are rotated so as to become optically aligned. In FIG. 5d is depicted that the left and right orientation of the surfaces provides misalignment of the unwanted astigmatism areas 65 and 66 of surfaces 61 and 62, respectively. The maximum, localized unwanted astigmatism for lens 60 of 1.70 diopters listed on Table 3. Example 10 An optical preform is produced containing a spherical, convex surface with a curvature of 6.00 diopters. The preform concave surface is a toric-progressive surface with a base spherical curvature of 6.00 diopters, a cylinder power of-2.00 diopters at an axis of 11.25 degrees, and near vision zone with a dioptric add power of 1.00 diopters. The near vision zone is centered along the 270 degree axis of the preform. A progressive addition glass mold for a left lens is provided to surface cast a UV curable resin layer onto the convex surface of the preform using conventional surface casting techniques. The mold has a 6.00 diopter base curvature and a 1.00 dioptric add power with the near vision zone along the 262 degree axis of the mold (8 degrees counterclockwise from the vertical). The preform is rotated counterclockwise, relative to the glass mold 11.25 degrees so that the cylinder axis falls at the mold"s 0 degrees axis, the axis desired for the lens. The rotational misalignment of the concave surface and convex surface near vision zones will be 11.25 - 8 = 3.25 degrees. The resultant lens has a distance power of 0.00 diopters, a cylinder power of-2.00 diopters at 0 degree axis, and a dioptric add power of 2.00 diopters. We Claim: 1. A process for producing a progressive addition lens for a lens wearer comprising the steps of: a) providing an optical preform comprising at least one surface having a predetermined first cylinder axis, a predetermined cylinder power such as 0.125 to 6.00 diopters and a predetermined first near vision zone position; b) providing a mold for casting a surface onto the optical preform, the mold comprising a second near vision zone that is aligned with the lens wearer"s near viewing pupil location; and c) positioning the preform in relation to the mold in order to provide the resulting tens with a cylinder axis desired for the lens wearer. 2. A process for producing a progressive addition lens for a lens wearer comprising the steps of: a) providing an optical preform comprising at least one surface having a first near vision zone position that Is aligned with the lens wearer"s near viewing pupil location; b) providing a mold for casting a surface onto the optical preform, the mold comprising a predetermined first cylinder axis, a predetermined cylinder power, and a predetermined second near vision zone position; and c) positioning the preform in relation to the mold in order to provide the resulting lens with a cylinder axis desired for the lens wearer. 3. The process as claimed in claims 1 or 2, wherein the mold is a mold suitable for casting a progressive addition surface onto the preform. 4. The process as claimed in claim 1, wherein the optical preform cylinder axis Is within about 0 to about 25 degrees of the lens" wearer"s cylinder axis. 5. The process as claimed in claim 1, wherein the optical preform surface Is the concave surface. 6. The process of claim 2, wherein the optical preform surface is the convex surface. 7. The process of claim 1, wherein the optical preform surface"s near vision zone is located so that its center is along the 270 degree axis of the preform. 8. The process of claim 1, wherein the optical preform cylinder axis is provided is one of a group that is less than the 180 possible axis orientations. 9. The process of claim 1, wherein the optical preform cylinder axis is provided at one of+11.25, +33.75, + 56.25, +78.75, + 101.25, +123.75, +146.25, or +168.75 degrees relative to the three o"clock position on the optical preform. 10. The process of claim 8, wherein the optical preform surface"s near vision zone center is located along the 270 degree axis of the optical preform. 11. The process of claim 9, wherein the optical preform surface"s near vision zone center is located along the 270 degree axis of the optical preform. 12. The process of claim 1, wherein the cast layer is cast onto the convex surface of the optical preform. 13. The process of claim 1, wherein the mold near vision zone is at a position that is on either side of the 270 degree axis of the mold. 14. The process of claim 13, wherein the near vision zone position is within about 0 to about 20 degrees of the 270 degree axis. 15. A process for producing a progressive addition lens for a lens wearer comprising the steps of: a.) providing an optical preform comprising a concave surface having a predetermined first cylinder axis, a predetermined cylinder power and a predetermined first near vision zone position; b.) providing a mold for casting a surface onto the optical preform"s convex surface, the mold comprising a second near vision zone that is aligned with the lens wearer"s near viewing pupil location; and c.) positioning the preform in relation to the mold in order to provide the resulting lens with a cylinder axis desired for the lens wearer. 16. The process of claim 15, wherein the mold is a mold suitable for casting a progressive addition surface onto the preform. 17. The process of claim 15, wherein the optical preform cylinder axis is within about 0 to about 25 degrees of the lens" wearer"s cylinder axis. 18. The process of claim 15, wherein the optical preform surface"s near vision zone is located so that its center is along the 270 degree axis of the preform. 19. The process of claim 15, wherein the optical preform cylinder axis is provided is one of a group of about 20 possible axis orientations. 20. The process of claim 15, wherein the optical preform cylinder axis is provided at one of +11.25, +33.75, + 56.25, +78.75, + 101.25, +123.75, +146.25, or +168.75 degrees relative to the three o"clock position on the optical preform. 21. The process of claim 19 or 20, wherein the optical preform surface"s near vision zone center is located along the 270 degree axis of the optical preform. 22. The process of claim 15, wherein the mold near vision zone is at a position that is on either side of the 270 degree axis of the mold. 23. The process of claim 22, wherein the near vision zone position is within about 0 to about 20 degrees of the 270 degree axis. 24. A process for producing a progressive addition lens for a lens wearer comprising the steps of: a.) providing an optical preform comprising a concave surface having a predetermined first cylinder axis that is within about 0 to about 25 degrees of the lens wearer"s cylinder axis, a predetermined cylinder power and a predetermined first near vision zone position that is located so that the center of the near vision zone is along the 270 degree axis of the optical preform; b.) providing a mold for casting a progressive addition surface onto the optical preform"s convex surface, the mold comprising a second near vision zone that is aligned with the lens wearer"s near viewing pupil location; and c.) positioning the preform in relation to the mold in order to provide the resulting lens with a cylinder axis desired for the lens wearer. 25. The process of claim 24, wherein the predetermined first cylinder axis is within about 11 degrees of the lens wearer"s cylinder axis. 26. The process of claim 24, wherein the optical preform cylinder axis is one of +11.25, +33.75, + 56.25, +78.75, + 101.25, +123.75, +146.25, or +168.75 degrees relative to the three o"clock position on the optical preform 27. The process of claim 26, wherein the predetermined first cylinder axis is within about 11 degrees of the lens wearer"s cylinder axis. 28. The process of claim 24, wherein the mold near vision zone is at a position that is on either side of the 270 degree axis of the mold. 29. The process of claim 28, wherein the near vision zone position is within about 0 to about 20 degrees of the 270 degree axis. 30. A progressive addition lens produced by the process of claim 1. 31. A progressive addition lens produced by the process of claim 15. 32. A progressive addition lens produced by the process of claim 24. A process for producing a progressive addition lens for a lens wearer comprising the steps of: a) providing an optical perform comprising at least one surface having a predetermined first cylinder axis, a predetermined cylinder power such as 0.125 to 6.00 diopters and a predetermined first near vision zone position; b) providing a mold for casting a surface onto the optical perform, the mold comprising a second near vision zone that is aligned with the lens wearer"s near viewing pupil location; and c) positioning the perform in relation to the mold in order to provide the resulting lens with a cylinder axis desired for the lens wearer.

Full Text

METHODS FOR PRODUCING PROGRESSIVE ADDITION LENSES
Field of the Invention
The present invention relates to multifocal ophthalmic lenses. In particular,
the invention provides progressive addition lenses in which unwanted legs
astigmatism is reduced without functional compromise of the distance and channel
widths through the intermediate and near vision zones, as compared to conventional
progressive addition lenses.
Background of the Invention
The use of ophthalmic lenses for the correction of ametropia is well known.
For example, multifocal lenses, such as progressive addition lenses ("PAL"s"), are
used for the treatment of presbyopia. The surface of a PAL provides far,
intermediate, and near vision in a gradual, continuous progression of vertically
increasing dioptric power from far to near focus, or top to bottom of the lens.
PAL"s are appealing to the wearer because PAL"s are free of the visible
ledges between the zones of differing dioptric power that are found in other
multifocal lenses, such as bifocals and trifocals. However, an inherent disadvantage
in PAL"s is unwanted lens astigmatism, or astigmatism introduced or caused by one
or more of the lens" surfaces. Generally, the unwanted lens astigmatism is located
on either side of the near vision zone of the lens and, at or near its approximate
center, reaches a maximum level that corresponds approximately to the near vision
dioptric add power of the lens.
Generally, a PAL with a 2.00 diopter add power and 15 mm channel length
will have about a 2.00 diopter maximum, localized unwanted astigmatism. The
channel width of the lens will be approximately 6 mm in which the unwanted
astigmatism is less than or equal to a 0.75 diopter threshold value.
Any number of lens designs have been tried in attempting to either or both
reduce unwanted astigmatism or increase the minimum channel width. However,
current state-of-the-art progressive addition lenses provide only minimal decreases
in unwanted astigmatism while having large areas in the lenses" peripheries that are
unusable due to unwanted astigmatism. Thus, a need exists for a PAL that reduces
maximum, localized unwanted astigmatism and, at the same time, provides an
increase in the minimum channel width.
Brief Description of the accompanying Drawings
FIG. la is a side view of a lens of the invention.
FIG. lb is an astigmatism map of the lens of FIG. 1a
FIG. 2a is a side view of a lens of the invention.
FIG. 2b is an astigmatism map of the lens of FIG. 2a.
FIG. 3 is a side view of a lens of the invention.
FIG. 4a is a side view of the lens of the invention.
FIG. 4b is an astigmatism map of the lens of FIG. 4a
FIG. 5 a is a side view of a lens of the invention.
FIG. 5b is an astigmatism map of a progressive surface of the lens of FIG.
5a.
FIG. 5c is an astigmatism map of a progressive surface of the lens of FIG.
5a.
FIG. 5d is an astigmatism map of the lens of FIG. 5a.
Description of the Invention and its Preferred Embodiments
The present invention provides progressive addition lenses, as well as
methods for their design and production, in which the maximum, localized unwanted
astigmatism that is associated with a given dioptric add power is reduced compared
to prior art lenses. Additionally, the distance width, or width about the optical center
of the lens that is free of about 0.50 diopters or more of unwanted astigmatism, and
minimum channel width of the lens is suitable for use by the lens wearer.
For purposes of the invention, by "channel" is meant the corridor of vision
that is free of astigmatism of about 0.75 diopters or greater when the wearer"s eye is
scanning from the distance zone to the near zone and back. By "lens" or "lenses" is
meant any ophthalmic lens including, without limitation, spectacle lenses, contact
lenses, intraocular lenses and the like. Preferably, the lens of the invention is a
spectacle lens.
It is one discovery of the invention that maximum, localized astigmatism
may be reduced by combining two or more progressive addition surfaces each
providing a dioptric add power that combines with that of the other surface or
surfaces to produce a lens of a higher dioptric add power than that of the surfaces
individually. By "dioptric add power" is meant the amount of dioptric power
difference between the near and far vision zones of a progressive addition surface.
The lens of the invention exhibits less maximum, localized unwanted astigmatism
and a wider channel than would be expected by producing a lens with the same
dioptric add power using only a single progressive addition surface. Further, it is a
discovery of the invention that the use of more than one progressive addition surface
ensures that the distance dioptric power and the total dioptric add power needed to
correct the wearer"s vision are uncompromised. It is yet another discovery of the
invention that when the progressive surfaces" dioptric add power areas are
misaligned with respect to one another, the resultant total maximum, localized
unwanted astigmatism of the lens is less than the sum of the maximum, localized
unwanted astigmatism contributed by the individual dioptric add powers of each
progressive addition surface.
By "progressive addition surface" is meant a continuous, aspheric surface
having far and near vision zones and a zone of increasing dioptric power connecting
the far and near vision zones. By "maximum, localized unwanted astigmatism" is
meant the highest, measurable level of astigmatism in an area of unwanted
astigmatism on a lens surface.
In one embodiment, the lens of the invention comprises, consists essentially
of, and consists of: a.) a first progressive addition surface having one or more areas
of maximum, localized unwanted astigmatism and a first dioptric add power; and
b.) a second progressive addition surface having one or more areas of maximum,
localized unwanted astigmatism and a second dioptric add power, the progressive
addition surfaces disposed in relation to each other so that a portion or all of the
areas of maximum, localized unwanted astigmatism are misaligned and wherein the
dioptric add power of the lens is the sum of the first and second dioptric add powers.
In another embodiment, the invention provides a process for producing a lens
comprising, consisting essentially of, and consisting of the steps of: a.) providing at
least a first and a second progressive addition surface, the first progressive addition
surface having one or more areas of maximum, localized unwanted astigmatism and
a first dioptric add power and the second progressive addition surface having one or
more areas of maximum, localized unwanted astigmatism and a second dioptric add
power; and b.) disposing the first and second progressive addition surfaces so that a
portion or all of the areas of maximum, localized unwanted astigmatism are
misaligned and the dioptric add power of the lens is the sum of the first and second
dioptric add powers.
By "misaligned" is meant that the surfaces, and thus the areas of unwanted
astigmatism, are arranged or disposed in relation to one another so that a portion or
all of the areas of maximum, localized unwanted astigmatism of one surface do not
substantially coincide with one or more areas of maximum, localized unwanted
astigmatism of the other surface. Preferably, the misalignment is such that no area
of maximum, localized unwanted astigmatism of a surface substantially coincides
with that of the other surface.
The progressive addition surfaces used in the lens of the invention may be
misaligned by any of a number of methods. For example, the optical centers of the
surfaces may be shifted either or both laterally or vertically with respect to each
other. By "optical center" is meant the point on a surface intersected by the optical
axis of the lens. One ordinarily skilled in the art will recognize that, if the optical
centers are shifted laterally, the minimum channel width is reduced by the extent of
the shift. Thus, a progressive addition lens design using a lateral shift preferably
uses progressive addition surfaces with wider channel widths to compensate for the
diminution in channel width caused by the shift.
Alternatively, if the optical centers of the surfaces are shifted vertically, the
channel length will be increased. By "channel length is meant the distance along the
central meridian of the surface between the optical center and the top end of the near
vision zone. Thus, a design using such a shift preferably uses progressive addition
surfaces with shorter channel lengths in compensation.
As yet another alternative, maintaining the optical centers of the progressive
surfaces coincident with each other, the centers may be rotated with respect to one
another. In a preferred embodiment, each surface is designed so that it is
asymmetric about the center line of its channel. In this case, the areas of maximum,
localized unwanted astigmatism of the surfaces do not substantially coincide on
rotation of the optics about an axis joining the surfaces" optical centers. By
"asymmetric" is meant that the power and astigmatism maps of the surface are
asymmetric about the center meridian of the surface.
The lateral and vertical shifts are done in such a way as to preserve the
distance and near vision dioptric powers of the lens. In order to minimize the
introduction of lens prism power, the shifts must occur so that the optical center of
one progressive addition surface is shifted along a curve that is parallel to the
distance curve of the other progressive addition surface. In the case of rotations, the
surfaces are rotated about their optical centers so that the distance and near powers
are substantially unaffected. One ordinarily skilled in the art will recognize that the
rotational misalignment may be in addition to the misalignment carried out for
purposes of reducing unwanted astigmatism.
The amount of misalignment, or the vertical shift, lateral shift or rotation of
optical centers, is an amount sufficient to prevent substantial superposition, or
coincidence, of the maximum, localized unwanted astigmatism areas of the
progressive addition surfaces. More specifically, it is believed that the misalignment
leads to a mismatch of the direction of the astigmatic vectors associated with one
surface relative to the corresponding astigmatic vectors of the other surface resulting
in the total maximum, localized unwanted astigmatism for the final lens being less
than that if the vectors were aligned. The lateral or vertical shift may be about 0.1
mm to about 10 mm, preferably about 1.0 mm to about 8 mm, more preferably about
2.0 mm to about 4.0 mm. Rotational shifts may be about 1 to about
40 degrees, preferably about 5 to about 30 degrees, more preferably about 10 to
about 20 degrees.
As yet another alternative for misalignment, each surface may be designed so
that the channel length of the surfaces are of different lengths. In this embodiment,
the areas of maximum, localized, unwanted astigmatism of the surfaces do not align
when the optical centers of the surfaces are brought into alignment. As a result, the
unwanted astigmatism is reduced compared to a lens of the same total dioptric add
power. The greater the difference between the channel lengths, the greater will be
the reduction in maximum, localized unwanted astigmatism. However, the channel
lengths must not be so large as to produce a mismatch in the near vision zones so
that the near vision of the lens wearer is compromised. The lens resulting from this
embodiment will have a channel length falling between that of each surface and
dependent upon the dioptric add power contributed by each surface to the total
dioptric add power of the lens. The channel length difference between the surfaces
may be about 0.1 mm to about 10 mm, preferably about 1 mm to about 7 mm, more
preferably about 2 mm to about 5 mm.
The progressive addition surfaces may each be independently on the convex
or concave surface of the lens or in a layer between the outer concave and outer
convex surfaces of the lens. Other surfaces, such as spheric and toric surfaces,
designed to adapt the lens to the ophthalmic prescription of the lens" wearer may be
used in combination with, or in addition to, one or more of the progressive addition
surfaces.
For example, one of the progressive addition surfaces, preferably a concave
surface, may be combined with a toric surface to provide a toric progressive surface
having a dioptric add power and a cylinder power at a particular axis. In the case of
a concave, toric progressive surface, the convex surface preferably is a non-toric
surface.
In order to both provide the desired dioptric add power and correct for the
lens wearer"s astigmatism, each of the surfaces" near vision zones may be aligned
with the wearer"s pupil location during near viewing and the cylinder axis of the
toric progressive surface placed so as to correspond to the wearer"s prescription.
However, this method necessitates that a toric progressive surface be provided at
each of the possible 180 degree cylinder axes orientations to provide a full
prescriptive range of lenses. It is yet another discovery of this invention that the
dioptric add power decreases slowly moving horizontally away from the center of
the near vision zone to the surface"s periphery. Given this fact, a rotational
misalignment of the surfaces" near vision zones of about + or - about 1 to about 25,
preferably + or - about 1 to about 15, more preferably + or - about 1 to about 13
degrees may be used while achieving the desired lens dioptric add power. This
discovery permits limiting the number of cylinder axis and near vision zone
positions used so that a toric progressive surface need not be provided at each
cylinder axis degree.
More specifically, a preferred process for producing a lens with a
toric progressive surface is as follows. An optical preform is selected, the preform
having a concave surface with a predetermined cylinder power, predetermined
cylinder axis, and predetermined near vision zone location. By "optical preform" or
"preform" is meant a shaped, optically transparent article capable of refracting light
and possessing a convex and a concave surface, which article is suitable for use in
producing a spectacle lens. The cylinder power preferably is the power required by
the lens wearer. The predetermined cylinder axis may be any cylinder axis, but
preferably is within a set number of degrees of the lens wearer"s required cylinder
axis. The preform cylinder axis may be within about 0 to about 25 degrees,
preferably about 0 to about 20 degrees, more preferably about 0 about 11 degrees of
the required cylinder axis desired for the lens" wearer. Preferably, the cylinder axis
orientation selected is one of a group of orientations that is less than the 180 possible
orientations, more preferably the axis being one of a group of about 20 orientations,
most preferably the orientation is +11.25, +33.75, + 56.25, +78.75, + 101.25,
+123.75, +146.25, and +168.75 degrees relative to the three o"clock position on the
preform.
The preform"s concave surface near vision zone may be provided at any
convenient position, but preferably is located so that its center is along the 270
degree axis of the preform. In a more preferred embodiment, preform cylinder axes
are provided at+11.25, +33.75, + 56.25, +78.75, + 101.25, +123.75, +146.25, or
+168.75 degrees relative to the three o"clock position on the preform and the near
vision zone center is located along the 270 degree axis, the six o"clock position.
A convex surface is provided for the lens by using a mold suitable for casting
the surface onto the preform. Preferably, the mold is suitable for the casting of a
progressive surface. The mold near vision zone may be provided at any convenient
position but preferably is at a position that is aligned with the near viewing pupil
position of the lens wearer. Typically, this position will be on either side of the 270
degree axis, the 6 o"clock position, of the mold depending on whether the left or
right lens is being fabricated. Preferably, the position is within about 0 to about 20,
more preferably about 5 to about 15, most preferably about 8 to about 10 degrees on
either side of the 270 degree axis.
The selected preform is positioned, or rotated, in relation to the mold
selected so that the cylinder axis of the resulting lens will be that required by the
lens wearer. For example, if the lens wearer"s required cylinder axis is 180 degrees
for the left eye and the optical preform cylinder power is at the 11.25 degree axis,
with the near vision zone at 270 degrees, the preform is rotated so that its cylinder
axis falls along the mold"s 180 degree axis. This aligns the cylinder axis of the
preform to the wearer"s required cylinder axis. It will be recognized that the rotation
of the preform in relation to the mold also produces a rotational misalignment of the
preform and mold near vision zones. However, this rotational misalignment is
tolerable up to about + or - 25 degrees for purposes of achieving the desired lens
dioptric add power.
Thus, in yet another embodiment, the invention provides a process for
producing a progressive addition lens for a lens wearer, and lenses produced by the
process, comprising, consisting essentially of and consisting of: a.) providing an
optical preform comprising at least one surface having a predetermined first
cylinder axis, a predetermined cylinder power, and a predetermined first near vision
zone position; b.) providing a mold for casting a surface onto the optical preform,
the mold comprising a second near vision zone position that is aligned with the lens
wearer"s near viewing pupil location; and c.) positioning the preform in relation to
the mold in order to provide the resulting lens with a cylinder axis desired for the
lens wearer.
In an alternative embodiment of the process, an optical preform is provided
with at least one surface, preferably the convex surface, having a near vision zone,
preferably a progressive addition surface. The near vision zone of this surface is
aligned with the lens wearer"s near viewing pupil location. A mold suitable for
casting a toric surface onto the preform is used, the mold having a predetermined
cylinder axis, cylinder power, and near vision zone location as above-described.
Thus, in an alternative embodiment, a process is provided for producing a
progressive addition lens for a lens wearer, and lenses produced by the process,
comprising, consisting essentially of and consisting of: a.) providing an optical
preform comprising at least one surface having a first near vision zone position that
is aligned with the lens wearer"s near viewing pupil location; b.) providing a mold
for casting a surface onto the optical preform, the mold comprising a predetermined
first cylinder axis, predetermined a cylinder power, and a predetermined second
near vision zone position; and c.) positioning the preform in relation to the mold in
order to provide the resulting lens with a cylinder axis desired for the lens wearer.

One ordinarily skilled in the art will recognize that any number of a wide
variety of predetermined cylinder axes and near vision zone placements may be
used. However, it is preferred that the predetermined cylinder axes and near vision
zone placements be selected from those shown on Table 1 for the listed lens cylinder
axis prescription requirements.
For the lenses and processes of the invention, the dioptric add power of each
of the progressive addition surfaces used in the invention is selected so that the sum
of their dioptric add powers is substantially equal to the value needed to correct the
lens wearer"s near vision acuity. Additionally, the dioptric add power of each
surface is selected in view of the maximum, localized unwanted astigmatism
associated with a given near dioptric power. The dioptric add power of the
progressive addition surfaces may be each independently from about + 0.01 diopters
to about +3.00 diopters, preferably from about +0.25 diopters to about +2.00
diopters, more preferably about +0.50 to about +1.50 diopters.
Similarly, the distance and near dioptric powers for each surface are selected
so that the sum of the powers is the value needed to correct the wearer"s distance
and near vision. Generally, the distance dioptric power for each surface will be
within the range of about 0.25 diopters to about 8.50 diopters. Preferably, the
dioptric power of the distance zone of the concave surface may be + or - about
2.00 to about 5.50 diopters and for the convex surface, + or - about 0.5 to about 8.00
diopters. The near vision dioptric power for each of the surfaces will be about 1.00
diopters to about 12.00 diopters. In those embodiments in which a cylinder power is
used, the cylinder power may be about -0.125 to about -6.00 diopters, preferably
about -0.25 to about -3.00 diopters.
The progressive addition surfaces and lenses of the invention may be formed
by any convenient method such as, without limitation, thermoforming, molding,
grinding, casting or the like. In a preferred method, an optical preform having a
progressive addition surface is used and a second progressive addition surface is cast
onto the preform. In a more preferred method, a preform the concave surface of
which is a progressive addition surface with a base spherical power and a cylinder
power is used and a progressive addition surface is formed on the front surface by
any convenient method, preferably by casting and more preferably by surface
casting.
The invention will be clarified further by a consideration of the following,
non-limiting examples.
Examples
Example 1
Referring to FIG. la, lens 10 of the invention is shown having convex
progressive addition surface 11 and concave progressive addition surface 12. Surface
11 has distance zone 13 with a curvature of 6.00 diopters and near zone 18 with a
curvature of 7.00 diopters. Surface 12 has distance zone 19 with a curvature of 6.00
diopters and near zone 21 with a curvature of 5.00 diopters. The resulting distance
power of the lens is 0.00 diopters and the dioptric add power of the lens is 2.00
diopters, 1.00 diopters contributed by each of surfaces 11 and 12. As shown in FIG.
la, the convex and concave optical centers 16 and 17, respectively, are shifted with
respect to each other by 4.0 mm.
FIG. lb is an astigmatism map of lens 10 illustrating the misalignment of the
surfaces. Areas 22 and 23 are of the unwanted astigmatism for surfaces 11 and 12,
respectively. The locations of the maximum, localized astigmatism 14 and 15 do not
overlap and, thus, are not additive. The maximum, localized unwanted astigmatism
value of 1.90 D for this lens is shown in Table 1 and is significantly lower than the
2.20 D that is found in a conventional PAL of the same near dioptric power.
Example 2
A lens with two progressive addition surfaces is used, the misalignment for
which is 8.00 mm. The misalignment results in a reduction of maximum localized u
unwanted astigmatism of 0.30 D compared to the prior art Lens of Table 1.
Example 3
As shown in FIGs. 2a and 2b, lens 20 with a concave progressive addition
surface 25 is seen. Surface 25 has distance and near zone curvatures of 6.00 and 5.00
diopters, respectively. Convex surface 24 with distance and near zone curvatures of
6.00 and 7.00 diopters is also shown. The optical center 27 of surface 25 is rotated
by a, an amount of 10 degrees, with respect to that of optical center 26 of convex
progressive surface 24. In FIG. 2b, the astigmatism map of lens 20 is shown. Areas
31 and 32 depict the areas of unwanted astigmatism for surfaces 24 and 25,
respectively. Maximum, localized unwanted astigmatism areas 28 and 29 for
surfaces 24 and 25, respectively, are also shown. Table 2 shows that the resulting
lens has a maximum, localized unwanted astigmatism of 1.90 diopters as compared to
2.10 diopters for a prior art lens.
Examples 4-6
The concave progressive addition surface of a lens is rotated around its
optical center by 20, 30, and 40 degrees with respect to the convex progressive
addition surface. The rotations result in maximum, localized unwanted astigmatisms
of 1.85, 1.75, and 1.41 diopters, respectively as listed on Table 2.
Example 7
FIG. 3 depicts a concave progressive addition surface 34 placed between
surfaces 33 and 35 of lens 30. Lens 30 is made of an optical preform 38 having a
refractive index of 1.60 and a cast layer 39 having a refractive index of 1.50.
Convex surface 33 of preform 38 has optical center 36, a distance curvature of 6.50
diopters and a near curvature of 8.50 diopters. Concave surface 34 of preform 38 has
optical center 37, a distance curvature ("DC") of 6.50 diopters and a near curvature
("NC") of 0.50 diopters derived by the formula:
wherein n1 is the refractive index of optical preform 38 and n2 is the refractive index
of layer 39. Optical center 37 is shifted vertically downwards 4 mm with respect to
optical center 36. Concave surface 35 of layer 39 includes a cylindrical power of
-2.00 D for correcting the wearer"s astigmatism. Lens 30 has a distance power of
0.00 diopters, a total dioptric add power of 3.00 diopters, arrived at by the 2.00
diopter dioptric add power of surface 33 and the 1.00 diopters dioptric add power of
surface 34 combined. The maximum, localized unwanted astigmatism is lower than
that of a conventional lens with a 3.00 diopters dioptric add power.
Example 8
In FIG. 4a is depicted lens 50 having convex surface 51 and concave surface
52. Surface 51 is a progressive addition surface with optical center 53. Surface 52 is
a combination progressive addition-toric surface having optical center 54 shifted
vertically downwards 4 mm with respect to optical center 53. FIG. 4b depicts the
astigmatism map for lens 50 showing the shift. Areas 55 and 56 are the areas of
unwanted astigmatism, 57 and 58 being their respective maximum, localized
unwanted astigmatism areas respectively, for surfaces 51 and 52. I-I is the toric axis
for surface 52. The overlap of the progressive addition surfaces are such that,
although the near and distance vision zones are preserved, the location of the
maximum, localized unwanted astigmatisms 57 and 58 of each surface do not
coincide and, thus, their effect is not additive.
Example 9
Lens 60 is depicted in FIG. 5a in which a left oriented, convex progressive
addition surface 61 shown combined with a right oriented, concave progressive
addition surface 62. Each surface is depicted individually in FIGs. 5b and 5c,
respectively. Optical centers 63 and 64 of each surface are rotated so as to become
optically aligned. In FIG. 5d is depicted that the left and right orientation of the
surfaces provides misalignment of the unwanted astigmatism areas 65 and 66 of
surfaces 61 and 62, respectively. The maximum, localized unwanted astigmatism
for lens 60 of 1.70 diopters listed on Table 3.
Example 10
An optical preform is produced containing a spherical, convex surface with a
curvature of 6.00 diopters. The preform concave surface is a toric-progressive
surface with a base spherical curvature of 6.00 diopters, a cylinder power of-2.00
diopters at an axis of 11.25 degrees, and near vision zone with a dioptric add power
of 1.00 diopters. The near vision zone is centered along the 270 degree axis of the
preform. A progressive addition glass mold for a left lens is provided to surface cast
a UV curable resin layer onto the convex surface of the preform using conventional
surface casting techniques. The mold has a 6.00 diopter base curvature and a 1.00
dioptric add power with the near vision zone along the 262 degree axis of the mold (8
degrees counterclockwise from the vertical). The preform is rotated
counterclockwise, relative to the glass mold 11.25 degrees so that the cylinder axis
falls at the mold"s 0 degrees axis, the axis desired for the lens. The rotational
misalignment of the concave surface and convex surface near vision zones will be
11.25 - 8 = 3.25 degrees. The resultant lens has a distance power of 0.00 diopters, a
cylinder power of-2.00 diopters at 0 degree axis, and a dioptric add power of 2.00
diopters.
We Claim:
1. A process for producing a progressive addition lens for a lens wearer
comprising the steps of: a) providing an optical preform comprising at
least one surface having a predetermined first cylinder axis, a
predetermined cylinder power such as 0.125 to 6.00 diopters and a
predetermined first near vision zone position; b) providing a mold for
casting a surface onto the optical preform, the mold comprising a
second near vision zone that is aligned with the lens wearer"s near
viewing pupil location; and c) positioning the preform in relation to the
mold in order to provide the resulting tens with a cylinder axis desired
for the lens wearer.
2. A process for producing a progressive addition lens for a lens wearer
comprising the steps of: a) providing an optical preform comprising at
least one surface having a first near vision zone position that Is aligned
with the lens wearer"s near viewing pupil location; b) providing a mold
for casting a surface onto the optical preform, the mold comprising a
predetermined first cylinder axis, a predetermined cylinder power, and
a predetermined second near vision zone position; and c) positioning
the preform in relation to the mold in order to provide the resulting lens
with a cylinder axis desired for the lens wearer.
3. The process as claimed in claims 1 or 2, wherein the mold is a mold
suitable for casting a progressive addition surface onto the preform.
4. The process as claimed in claim 1, wherein the optical preform cylinder
axis Is within about 0 to about 25 degrees of the lens" wearer"s cylinder
axis.
5. The process as claimed in claim 1, wherein the optical preform surface
Is the concave surface.
6. The process of claim 2, wherein the optical preform surface is the convex
surface.
7. The process of claim 1, wherein the optical preform surface"s near vision
zone is located so that its center is along the 270 degree axis of the preform.
8. The process of claim 1, wherein the optical preform cylinder axis is provided
is one of a group that is less than the 180 possible axis orientations.
9. The process of claim 1, wherein the optical preform cylinder axis is provided
at one of+11.25, +33.75, + 56.25, +78.75, + 101.25, +123.75, +146.25, or +168.75
degrees relative to the three o"clock position on the optical preform.
10. The process of claim 8, wherein the optical preform surface"s near vision
zone center is located along the 270 degree axis of the optical preform.
11. The process of claim 9, wherein the optical preform surface"s near vision
zone center is located along the 270 degree axis of the optical preform.
12. The process of claim 1, wherein the cast layer is cast onto the convex surface
of the optical preform.
13. The process of claim 1, wherein the mold near vision zone is at a position
that is on either side of the 270 degree axis of the mold.
14. The process of claim 13, wherein the near vision zone position is within
about 0 to about 20 degrees of the 270 degree axis.
15. A process for producing a progressive addition lens for a lens wearer
comprising the steps of: a.) providing an optical preform comprising a concave
surface having a predetermined first cylinder axis, a predetermined cylinder power
and a predetermined first near vision zone position; b.) providing a mold for casting
a surface onto the optical preform"s convex surface, the mold comprising a second
near vision zone that is aligned with the lens wearer"s near viewing pupil location;
and c.) positioning the preform in relation to the mold in order to provide the
resulting lens with a cylinder axis desired for the lens wearer.
16. The process of claim 15, wherein the mold is a mold suitable for casting a
progressive addition surface onto the preform.
17. The process of claim 15, wherein the optical preform cylinder axis is within
about 0 to about 25 degrees of the lens" wearer"s cylinder axis.
18. The process of claim 15, wherein the optical preform surface"s near vision
zone is located so that its center is along the 270 degree axis of the preform.
19. The process of claim 15, wherein the optical preform cylinder axis is
provided is one of a group of about 20 possible axis orientations.
20. The process of claim 15, wherein the optical preform cylinder axis is
provided at one of +11.25, +33.75, + 56.25, +78.75, + 101.25, +123.75, +146.25, or
+168.75 degrees relative to the three o"clock position on the optical preform.
21. The process of claim 19 or 20, wherein the optical preform surface"s near
vision zone center is located along the 270 degree axis of the optical preform.
22. The process of claim 15, wherein the mold near vision zone is at a position
that is on either side of the 270 degree axis of the mold.
23. The process of claim 22, wherein the near vision zone position is within
about 0 to about 20 degrees of the 270 degree axis.
24. A process for producing a progressive addition lens for a lens wearer
comprising the steps of: a.) providing an optical preform comprising a concave
surface having a predetermined first cylinder axis that is within about 0 to about 25
degrees of the lens wearer"s cylinder axis, a predetermined cylinder power and a
predetermined first near vision zone position that is located so that the center of the
near vision zone is along the 270 degree axis of the optical preform; b.) providing a
mold for casting a progressive addition surface onto the optical preform"s convex
surface, the mold comprising a second near vision zone that is aligned with the lens
wearer"s near viewing pupil location; and c.) positioning the preform in relation to
the mold in order to provide the resulting lens with a cylinder axis desired for the
lens wearer.
25. The process of claim 24, wherein the predetermined first cylinder axis is
within about 11 degrees of the lens wearer"s cylinder axis.
26. The process of claim 24, wherein the optical preform cylinder axis is one of
+11.25, +33.75, + 56.25, +78.75, + 101.25, +123.75, +146.25, or +168.75 degrees
relative to the three o"clock position on the optical preform
27. The process of claim 26, wherein the predetermined first cylinder axis is
within about 11 degrees of the lens wearer"s cylinder axis.
28. The process of claim 24, wherein the mold near vision zone is at a position
that is on either side of the 270 degree axis of the mold.
29. The process of claim 28, wherein the near vision zone position is within
about 0 to about 20 degrees of the 270 degree axis.
30. A progressive addition lens produced by the process of claim 1.
31. A progressive addition lens produced by the process of claim 15.
32. A progressive addition lens produced by the process of claim 24.
A process for producing a progressive addition lens for a lens wearer comprising the
steps of: a) providing an optical perform comprising at least one surface having a
predetermined first cylinder axis, a predetermined cylinder power such as 0.125 to
6.00 diopters and a predetermined first near vision zone position; b) providing a
mold for casting a surface onto the optical perform, the mold comprising a second
near vision zone that is aligned with the lens wearer"s near viewing pupil location;
and c) positioning the perform in relation to the mold in order to provide the
resulting lens with a cylinder axis desired for the lens wearer.

Documents:

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Patent Number

216900

Indian Patent Application Number

853/CAL/1999

PG Journal Number

12/2008

Publication Date

21-Mar-2008

Grant Date

19-Mar-2008

Date of Filing

22-Oct-1999

Name of Patentee

ESSILOR INTERNATIONAL (COMPAGNIE GENERALE D'OPTIQUE)

Applicant Address

147 RUE DE PARIS, F-94220 CHARENTON-LE-PONT,

Inventors:

#	Inventor's Name	Inventor's Address
1	MENEZES EDGAR V.	6558 HIDDEN WOODS DEIVE ROANOKE, VA 24018
2	MERRITT JAMES S.	10557 ;OTT;E CATAWBA CREEL RPAD, TROUTVILLE, VA 24175
3	KOKONASKI WILLIAM	6173 BURNHAM ROAD, ROANOKE, VA 24018

PCT International Classification Number

A61B 8/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	09/315477	1999-05-20	U.S.A.