Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
  • G02C7/06—Lenses; Lens systems ; Methods of designing lenses bifocal; multifocal ; progressive
  • G02C7/061—Spectacle lenses with progressively varying focal power
  • G02C7/063—Shape of the progressive surface
  • G02C7/065—Properties on the principal line
• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
  • G02C7/06—Lenses; Lens systems ; Methods of designing lenses bifocal; multifocal ; progressive
  • G02C7/061—Spectacle lenses with progressively varying focal power

Definitions

• the present invention relates to a progressive ophthalmic lens, which has an additional zone of intermediate vision.
• Progressive lenses of ophthalmic spectacles are widely used, in particular to correct visual defects of presbyopia of wearers of these glasses.
• a progressive lens has an optical power which varies between different points thereof, so that the correction of the visual defect which is brought by the lens is adapted as a function of the distance of an object which is observed by the wearer.
• a far vision zone is formed in the upper part of the lens, which is dedicated to the observation of distant objects, that is to say objects that are located at a distance of 1 , 5 meters or more from the wearer.
• a near vision zone is formed in the lower part of the lens, which is dedicated to the observation of close objects, located within 1.0 meter of the wearer, in particular about forty centimeters from his eyes.
• the optical power of each progressive lens varies continuously between these near and far vision areas, so that an intermediate zone which is located between them is adapted to observe objects between 1.0 meter and 1, 5 meters from the wearer.
• the intermediate vision zone allows the wearer to clearly perceive an object which is located at a distance between 1.0 and 1.5 meters from his eyes, without moving his head if this object is located in a direction around or slightly inclined below the horizontal.
• progressive lenses with four zones have been proposed several times. Compared to the usual progressive lenses recalled above, they have an additional zone which is located below the near vision zone, and which is adapted for intermediate distance vision. Compared to progressive three-zone lenses, this additional zone of intermediate vision allows the wearer to clearly see an object or obstacle that is located on the ground in front of his feet.
• Such a progressive four-zone lens for ophthalmic spectacles comprises at least one complex surface with variable curvature, a prismatic reference point and a mounting cross, and is adapted to be arranged in front of an eye of the wearer so that a scanning of the The wearer's direction of gaze through the lens defines a meridian line that corresponds to the intersection trace of the gaze direction with this surface.
• This meridian line connects an upper edge and a lower edge of the lens passing successively by a far vision point, the mounting cross, the prismatic reference point and a near vision point.
• the mounting cross is 4 mm above the reference point and may correspond to the direction of horizontal gaze when the wearer is standing
• the optical power along the meridian line corresponds to an ophthalmic correction in far vision in a first segment of this line which is located above the vision point of It then increases to a maximum value that is reached at the near vision point and then decreases from that near vision point over a specified length towards the lower edge.
• the lens thus has an optical power addition between far and near vision points and the additional area of intermediate vision near the lower edge
• An object of the present invention is then to provide a progressive lens having an additional zone of intermediate vision, and which meets this need.
• the invention proposes a progressive lens with additional zone of intermediate vision, located below the zone. near vision, of the type described above, whose optical power addition is greater than or equal to 2.0 diopters, and for which the optical power has a threshold of increase along the meridian line which is substantially located at the mounting cross, away from the prismatic reference point
• the characteristic that the threshold of increase in optical power is located along the meridian line at the mounting cross and away from the prismatic reference point means that a first variation of the optical power calculated between the far vision point and the mounting cross is less than 10% of the addition of optical power, in absolute value. Most often, this first absolute variation is less than 5%.
• a second variation of the optical power which is calculated between the far vision point and the prismatic reference point is greater than 25%, in absolute value, advantageously greater than 30%.
• the invention also relates to a lens as defined above, after the lens has been removed from the frame, without this additional zone of intermediate vision being entirely eliminated during the shaping operation. cut in accordance with the dimensions of a glass housing in a frame
• the lens may have a lower edge after trimming which is at a distance less than 23 mm from the mounting cross,
• the invention is therefore compatible with the use of an eyeglass frame which has a reduced vertical dimension, and in which the lens is intended to be assembled.
• the point of near vision of the lens, where the optical power reaches the maximum value along the meridian line may be less than 15 mm below the mounting cross.
• the near vision point may be between 10 mm and 12 mm. mm below the mounting cross
• the optical power along the meridian line has variations which are less than 0.5 diopter in a second segment of this meridian line, within the additional zone of intermediate vision This second segment is situated below the point of near vision, between a point which is situated at a distance less than or equal to 18 mm from the mounting cross and the lower edge of the lens
• the additional zone of intermediate vision is not a transition channel in which the optical power decreases regularly towards the lower edge It is rather a zone of vision through which the direction of the gaze can vary vertically while fixing objects which are located at almost identical intermediate distances, although at different heights A good comfort of vision through this additional zone results In particular, no visual fatigue is felt, nor the need to raise or lower the head vertically to adjust the height of the glass relative to the viewing distance and the height of an object observed through this additional area
• the optical power along the meridian line may furthermore have variations which are less than 0.25 diopters in a third segment of the meridian line which is located within the second segment. extend between a point which is at a distance of 22 mm or less from the mounting cross and the lower edge of the lens The comfort of use of the lens is then even higher
• the second segment and / or the third segment may have a length greater than 5 mm, or even greater than 10 mm, along the meridian line.
• the lens may have, in lateral parts thereof which are located on either side of the near vision point, an optical power which is lower than the value reached at the point near vision.
• the optical power may be less than half of the near-vision point value at two points of the lens that are horizontally 8 mm apart from and on each side of the near vision point. In this way, the far vision zone can be disengaged laterally, at least with respect to the optical power values, and thus provides the wearer with a wide viewing area that is wide, extending on either side. further down.
• a lens according to the invention can be adapted, in particular, to at least partially correct a presbyopia of the wearer in an area thereof which surrounds the near vision point.
• FIG. 1 is a general profile view of a lens according to FIG. invention
• FIGS. 2a and 2b are diagrams showing tangential and sagittal curvature variations, respectively for a first lens according to the invention which has an addition of 2.0 diopters, and a second lens according to the invention which has an addition of 2.5 diopters;
• FIGS. 3a and 3b are mean sphere and cylinder maps, respectively, for the first lens of FIG. 2a;
• a lens 1 for ophthalmic spectacles has an anterior face, denoted F1 in the figure, and a posterior face, denoted F2 and opposite to the face F1. Between these two faces, it consists of a refractive transparent medium which is usually homogeneous.
• the lens may be a finished spectacle lens, whose two faces F1 and F2 have definite shapes. It can then be a glass that is already cut to the dimensions of a glass housing of a pair of glasses. But the finished glass can also be considered before being cut out.
• the lens may be a semi-finished lens, of which only one face has a definitive shape, and the other face is intended to be machined subsequently according to the prescription of a wearer.
• the optical power of the lens is understood as the optical power of a finished glass that is obtained from the semi-finished glass. Most often, the anterior face of the semi-finished glass is final, and the posterior face is that which is intended to be machined in recovery.
• ophthalmic lens means both a finished glass and a semi-finished glass. When not cut out, the lens has a peripheral edge which is most often circular, for example with a diameter of 60 mm (millimeter).
• the terms "on”, “under”, “above”, “below” and “lateral” are used to qualify portions or points of the lens relative to a reference position of the lens used by the wearer.
• This position which is called the use position of the lens by the wearer, corresponds to a vertical holding of the wearer's head equipped with the frame in which the lens is assembled.
• the F1 and F2 faces of the lens, respectively anterior and posterior are thus designated with respect to their situation when the lens is thus used by the wearer.
• the complex surface of the progressive lens is located on the rear face F2.
• the face F2 has a mean sphere and a cylinder which vary continuously along this face. It is recalled that the mean sphere (Sph) and the cylinder (CyI) of a complex surface, estimated at a point thereof, are respectively given by the following formulas:
• n is the refractive index of the lens material at the point in question
• R1 and R2 respectively denote the maximum and minimum radii of the complex surface at the same point, measured in two perpendicular directions.
• the numerical values which are indicated in FIGS. 2a, 2b, 3a, 3b, 4a and 4b correspond to lenses which consist of the same transparent homogeneous material whose refractive index n is equal to 1. 591.
• the anterior face F1 of the lens 1 may be a series surface obtained during the molding of the lens. In particular, it can be spherical.
• the rear face F2 can be machined so as to confer on the lens the characteristics of the invention, by using one of the precision machining processes which are known to those skilled in the art, in particular a machining method with digital control.
• the addition of constant components of average sphere and cylinder to the local values which are indicated by the maps of FIGS. 3a, 3b, 4a and 4b makes it possible to obtain a lens which corresponds to an ophthalmic prescription established for the wearer.
• the rear face F2 can thus be further adapted so that the lens has, at the far vision point, optical power and astigmatism values which correspond to a prescription established for the wearer.
• the prismatic reference point which is denoted O, and which is associated with a prism value of The lens ;
• CM a mounting cross
• VL a distance vision reference point
• VP a near-vision reference point
• the mounting cross CM corresponds to the direction of horizontal gaze when the wearer is standing.
• the prismatic reference point O generally corresponds to the geometric center of the lens.
• the points O, CM, VL and VP are initially defined on the anterior face F1 of the lens 1. Reference points corresponding to these are defined on the rear face F2. These points of the face F2 may be respectively opposite the points O, CM, VL and VP, or else be shifted with respect thereto along the path of light rays passing through the points O, CM, VL and VP of the F1 side. Alternatively, the reference points of the face F2 can be defined from the points O,
• the posterior face F2 of the lens 1 is then marked by two Cartesian axes expressed in millimeters: X for the horizontal axis and Y for the vertical axis, the latter being positively oriented upwards.
• the near vision point VP is located below O 1 by being laterally offset (parallel to the X axis) with respect to VL. The direction of VP shift is reversed between a right lens and a left lens.
• An LM line which is called the main meridian line, connects the points VL, CM, O and VP. It corresponds to the trace on the lens of the direction of gaze when the wearer observes successively objects that are located in front of him at varying heights and distances.
• FIGS. 2a and 2b illustrate the variations of the tangential and sagittal curvatures along the meridian line LM, the posterior faces of two distinct lenses in accordance with the invention, having, respectively, addition values which are fixed by their posterior faces. , and which are equal to 2.0 and 2.5 diopters.
• the tangential and sagittal curvatures, which are denoted respectively C1 and C2 are equal to the inverse of the radii of curvature R1 and R2 of formulas 1a and 1b recalled above.
• the optical power of a lens denoted OP for "Optical Power"
• OP optical Power
• the optical power for a given viewing direction results from the mean sphere and the cylinder of each of the faces F1 and F2 at the crossing points of these faces by a light ray which corresponds to the viewing direction.
• the addition of the lens 1 is then defined as the difference between the optical power values OP at the points VP and VL:
• Figures 3a and 4a are mean sphere maps of the posterior faces of the two lenses of Figures 2a and 2b, respectively. Each of these maps is limited by the peripheral edge of the corresponding lens, and indicates the value of the average sphere for each point of the posterior face of the lens.
• the lines that are shown on these maps are iso-sphere lines, which connect points of the posterior face of each lens that correspond to the same average sphere value. This value is indicated in diopters for some of these lines.
• Figures 3b and 4b are cylinder mappings.
• the lines which are carried on these are iso-cylinder lines, which connect points of the posterior face of each lens which correspond to the same cylinder value.
• the average sphere value is maximum at the point VP
• the vertical distance between the near vision point VP and the mounting cross CM is then 12 mm, for both lenses
• the average sphere is substantially zero, in particular less than 0.25 diopters in the zone of the glass which is located above the far VL vision point. In particular, it is less than 0.25 diopters in the entire segment of the lens.
• the meridian line LM which extends between the point VL and the upper edge of the lenses This segment is called the first segment of the line LM and denoted S1 in the figures
• the diagrams 2a and 2b, as well as the maps 3a and 4a show that the average sphere increases between the points VL and VP, in the direction of VP, with a threshold of increase which is located substantially at the mounting cross CM
• the mean sphere remains less than 0.25 diopters on the meridian line LM between the point VL and the mounting cross CM, and becomes greater than 0.25 diopters near CM
• the value of average sphere is close to (A -
• the residual decay of the mean sphere to the lower edge is 0.50 diopters in a second segment S2 of the line LM connecting a point E thereof to the lower edge for the first lens ( Figures 2a, 3a, 3b). , addition of 2.0 diopters, as well as for the second lens (FIGS.
• the point E has for vertical coordinate -13 mm II is therefore located at 17 mm in below the mounting cross CM
• the residual decay of the mean sphere to the lower edge is 0.25 diopters in a third segment S3 of the line LM, between a point F of the segment S2 and the edge
• the point F has a vertical coordinate of approximately -15 mm, that is, it is 19 mm below the CM mounting cross.
• the mean sphere On both sides of the near vision point VP, on a horizontal line passing through the point VP, the mean sphere is less than its value at the point VP. Moreover, at the points B and B 'of this line which are distant of the VP point of 8 mm, the average sphere is less than half of its value at the point VP In this way, the mean sphere decreases rapidly in the lateral parts of the lens on both sides of the point VP The posterior face of the present lens then two large lateral extensions of the far vision zone, towards the bottom of the lens, in which the average sphere varies by an amount which is less than a quarter of the addition A, with respect to the sphere value average at far vision point VL
• FIGS. 3b and 4b show that the cylinder has zero values, or less than 0.25 diopters, in a first wide zone located on either side of the first segment S1, corresponding to the distant zone of vision of the lenses, as well as in a second zone located on either side of the second segment S2, corresponding to the additional zone of intermediate vision. These two zones are thus devoid of involuntary astigmatism.
• the invention has been described in detail for lenses whose posterior faces have complex shapes, and the anterior faces of spherical or toric shapes, it is understood that the invention may be similarly made for a lens whose anterior side is complex, and the posterior face is spherical or toric. Likewise, both faces can be complex.
• the variations of the optical power according to the invention then result from the combination of the mean sphere and cylinder variations of the two faces.
• the maps provided in the figures only correspond to two addition values which are given by way of examples, it is understood that the invention can be realized in the same way for any values of addition, greater than or equal to 2.0 diopters. In particular, it can be performed for addition values up to 4.0 diopters.

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• 2007
  • 2007-12-05 FR FR0708499A patent/FR2924824B1/fr active Active
• 2008
  • 2008-12-03 EP EP08862414A patent/EP2223181A2/de not_active Ceased
  • 2008-12-03 JP JP2010536515A patent/JP5535933B2/ja not_active Expired - Fee Related
  • 2008-12-03 US US12/746,190 patent/US8061838B2/en active Active
  • 2008-12-03 WO PCT/FR2008/052195 patent/WO2009077708A2/fr active Application Filing

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