Method for designing and machining an ophthalmic lens, method for manufacturing a bevelled lens and corresponding lenses

Method for designing an ophthalmic lens, which has one concave face and one convex face and an external perimeter, where said external perimeter has a thickness within a pre-established range, comprising:

• (a.i) taking physiological data and prescription data of a user's optical correction;
• (a.ii) selecting a frame, taking data of said frame, including the data of a perimeter of said frame, and taking data of positioning of the lens with respect to a user's eye, taking into account the selected frame;
• (b) defining a central area that has a central perimeter that coincides with the perimeter of said selected frame;
• (c) defining a temporal line that divides the central area into a nasal area and a temporal area, where the temporal line is outside an intersection between the convex face and a cone with an opening angle of at least 30°, an apex of which is in a center of rotation of the user's eye and which axis corresponds to an optical axis;
• (d) defining a useful perimeter formed by a combination of the nasal area of said central perimeter and said temporal line, and a useful area delimited by said useful perimeter;
• (e) establishing permissible thickness values for said central perimeter;
• (f) defining a surface to be machined on one of said concave and convex faces, so that said concave face and said convex face, together, comply with a certain, pre-established ophthalmic prescription in said useful area;
• (g) positioning said surface to be machined, provided on one of said concave and convex faces, with respect to the other of said concave and convex faces, so that said surface to be machined and its positioning with respect to the other of said concave and convex faces determines the thickness of the lens along said useful perimeter of said useful area, where each and every one of points in the nasal area of said central perimeter has a thickness that complies with the permissible thickness values;
• and
• (h) defining a transition area with a transition surface that extends between said useful perimeter of said useful area and said external perimeter, where said transition surface extends as a continuation of said surface to be machined and extends as far as said external perimeter, and where said transition surface is continual and its derivative is continuous on all points, including a joining line between said transition surface and said surface to be machined, and where said transition surface complies with the permissible thickness values in step (e) on a point of the temporal part of the central perimeter.