Patent ID: 8876288
Filing Date: 2014-11-04
Classification: G02C

Abstract:
1. A complex surface of a progressive multifocal ophthalmic lens having at every point thereon a value of mean sphere and a value of cylinder, the surface comprising: a far vision region having a reference point for far vision; a near vision region having a reference point for near vision; a surface addition defined as a difference in mean sphere between the reference point for near vision and the reference point for far vision; an intermediate vision region between the far vision region and the near vision region; a main meridian of progression passing through the three regions and dividing the surface into a temporal region and a nasal region, a portion on the meridian passing through the far vision region defining a vertical axis; a fitting cross; a prism reference point in the center of a segment connecting micro-engravings, the prism reference point defining, with the vertical axis of the meridian and a horizontal axis connecting the micro-engravings, a reference frame, the reference frame making it possible to define each of the points on the lens by a value on a y-axis relative to the vertical axis and a value on an x-axis relative to the horizontal axis, the prism reference point having a value of zero on the x-axis and on the y-axis; a disc grouping together all points on the lens having the same value on the x-axis and the same value on the y-axis as points situated within a circle in a plane of the reference frame of 50 mm diameter and centered on the prism reference point; a progression length less than 14.5 mm, the progression length being defined as a difference between a value on the y-axis of the fitting cross and a value on the y-axis of the point on the meridian where variation in mean sphere with respect the value of mean sphere at the reference point for far vision reaches 85% of surface addition; a difference in ratio between value of cylinder and surface addition is less than 0.2 in absolute value for every pair of points on the lens symmetrical with respect to the fitting cross and having the same y-axis value as the fitting cross, and an x-axis value less than 20 millimeters in absolute value; a first specific point having a value of cylinder equal to a maximum cylinder value from among the set of points on the lens located inside the nasal region and within the disc; a second specific point having a value of cylinder equal to a maximum cylinder value from among the set of points on the lens located inside the temporal region and within the disc; a first ratio between a maximum slope of cylinder for points on the lens having the same value on the x-axis and the same value on the y-axis as the points on segments connecting the fitting cross to the first and second specific points and the surface addition which is less than 0.095 per millimeter, and a second ratio between the maximum value of cylinder for the first and second specific points and the surface addition which is less than or equal to 0.85.