Series of progressive ophthalmic lenses
View Patent ↗A series of progressive ophthalmic lenses is proposed, which is indexed by optical power addition values of eyeglasses of spectacles to be made from these lenses. Each lens of the series determines a further gap between a value of the optical power for the near vision direction and a maximum value of the optical power which is obtained for a direction of gaze pointing below said near vision direction. The lenses of the series are adapted for postures of wearers that may vary as a function of the optical power addition values.
1. Series of progressive ophthalmic lenses, indexed by values of a set of parameters comprising an optical power addition of a spectacle eyeglass which can be produced from each lens of the series, between a far-vision reference direction and a near-vision reference direction through said eyeglass,
the far-vision reference direction being a direction of vision passing through a fitting cross marked on each lens,
the optical power addition value of each lens being inscribed on said lens,
each lens moreover determining a further difference between an optical power value for the near-vision reference direction and a maximum value of the optical power of an eyeglass which is produced from said lens, said maximum value of the optical power being reached for a direction of gaze pointing below the near-vision reference direction for a use position of the eyeglass,
the series of lenses being characterized in that said further difference, in absolute value and expressed in dioptres, is comprised
between 0.025×A 2 +0.055×A+0.01
and 0.0775 A 2 −0.06×A+0.175,
where A is the optical power addition expressed in dioptres, comprised between 0.25 dioptre and 5 dioptres.
2. Series according to claim 1 , in which, for each eyeglass obtained from a lens of the series, the absolute further difference between the maximum value of the optical power and the value of the optical power for the near-vision reference direction, is substantially equal to 0.06×A 2 −0.02×A+0.1.
3. Series according to claim 1 , in which the addition of an eyeglass obtained from a lens of the series, and also the further difference between the maximum value of the optical power of said eyeglass and the value of the optical power for the near-vision reference direction through said eyeglass, are determined by a final shape of a front face and/or of a rear face of the lens, with respect to the use position of the eyeglass.
4. Series according to any claim 1 , in which, for each eyeglass obtained from a lens of the series, the direction of gaze corresponding to the maximum value of the optical power forms an angle Δα with the near-vision reference direction, said angle Δα being comprised
between 2.5×A+2
and 5×A+6,
A being the optical power addition expressed in dioptres, and the angle Δα being expressed in degrees.
5. Series according to claim 4 , in which, for each eyeglass obtained from a lens of the series, the angle Δα between the direction of gaze corresponding to the maximum value of the optical power and the near-vision reference direction, is substantially equal to 3.75×A+3.65, A being the optical power addition expressed in dioptres.
6. Method for producing a progressive spectacle eyeglass intended for an identified wearer, comprising the following steps:
/1/ obtaining a series of progressive ophthalmic lenses according to claim 1 ;
/2/ obtaining an addition value prescribed for said wearer;
/3/ selecting a lens of the series, as a function of the prescribed addition value; and
/4/ producing the spectacle eyeglass from the selected lens.
7. Method according to claim 6 , according to which a far-vision correction prescribed for the wearer is moreover obtained in step /2/, and according to which step /4/ comprises a modification of the lens in a further machining operation, so that the eyeglass has an optical power for the far-vision reference direction through said eyeglass, which corresponds to the prescribed far-vision correction.
8. Method according to claim 7 , according to which the addition of an eyeglass obtained from a lens of the series, and also the further difference between the maximum value of the optical power of said eyeglass and the value of the optical power for the near-vision reference direction through said eyeglass, are determined by a final shape of only one face from a front face and a rear face of the lens, and according which the step /4/ comprises a machining of the other of the said faces.
9. Method according to claim 6 , comprising moreover a prior step according to which, for each lens of the series, the further difference between the maximum value of the optical power and the value of the optical power for the near-vision reference direction, for an eyeglass produced from said lens, is determined from postural values measured for wearers of progressive spectacle eyeglasses having the addition of said lens.
10. Method according to claim 9 , according to which, during the prior step and for each lens of the series, an angle between the direction of gaze corresponding to the maximum value of optical power for an eyeglass produced from said lens on the one hand, and the near-vision reference direction through said eyeglass on the other hand, is determined moreover from the postural values measured for wearers of progressive spectacle eyeglasses having the addition of said lens.
11. Method according to claim 9 , according to which the postural values comprise horopter values, values of a distance between an eye of the wearer and an object examined in near vision, and/or a vertical participation of the head of the wearer in a change of direction of gaze.