| 主权项 |
1. A complex surface of a progressive multifocal ophthalmic lens having at every point thereon a value of mean sphere and a cylinder value, 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 nasal region and a temporal 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 circle 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 second circle in a plane of the reference frame of 35 mm diameter and centered on a point located 8.5 mm below the fitting cross and offset horizontally to a nasal side by 1.25 mm; 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 the grouping circle;
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 to the value of mean sphere at the reference point for far vision reaches 85% of surface addition; a difference in ratio between cylinder value and surface addition 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 ratio between a maximum cylinder value or all of the points in the, grouping circle and a surface addition being less than 0.7; and a second ratio between a maximum cylinder value for all the points on the disc and a surface addition being less than or equal to 1.05.
|
