Progressive addition lenses
View Patent ↗The present provides progressive addition lens designs and lenses in which unwanted lens astigmatism is reduced as compared to conventional progressive addition lenses. The lenses of the invention containing at least one surface that is a composite of a progressive surface design and a regressive surface design.
1. A method for designing a progressive addition surface of a progressive addition lens comprising the steps of: a.) designing a progressive surface comprising at least one first area of unwanted astigmatism; b.) designing a regressive surface comprising at least one second area of unwanted astigmatism; and c.) combining the progressive and regressive surface designs to form a composite progressive surface design formed on at least one of the front and back surfaces of the lens, wherein the at least one first and second areas of unwanted astigmatism are substantially aligned.
2. The method of claim 1 , wherein each of the progressive and regressive surface designs is one of a hard design, a soft design, or a combination thereof.
3. The method of claim 1 , wherein each of the progressive and regressive surface designs are hard designs.
4. The method of claim 1 , wherein each of the progressive and regressive surface designs are soft designs.
5. The method of claim 1 , wherein a surface formed from the composite surface design exhibits maximum, localized unwanted astigmatism that is less than about 0.125 diopters than the sum of an absolute value of the maximum, localized unwanted astigmatism of each of the progressive and regressive surfaces.
6. The method of claim 1 , wherein the composite surface design comprises more than one area of maximum, localized unwanted astigmatism on each side of a composite surface's channel.
7. The method of claim 1 , wherein the progressive and regressive surface designs are expressed as sag departures from a base curvature.
8. The method of claim 7 , wherein the base curvature is a concave curvature or a convex curvature.
9. The method of claim 1 , wherein step c.) is carried out by summing a progressive surface and regressive surface design sag values according to the following equation:
Z ( x, y )=Σ a i Z i ( x, y )
wherein Z is the composite surface sag value departure from a base curvature at point (x, y), Z i is the sag departure for the ith surface to be combined at point (x, y) and a i are coefficients.