A method for injection molding of a weld line free minus power lens element comprising a wafer of thermoplastic material made from polycarbonate with a weight average molecular weight of less than 26,000 g/mol, comprising: injecting a melt of thermoplastic material comprising at least one UV absorber at a temperature higher than a glass transition temperature (Tg) of the thermoplastic material and at a speed of not more than 25 mm/s in an initial molding cavity delimited by two facing mold inserts, wherein the thermoplastic material is polycarbonate with a weight average molecular weight of less than 26,000 g/mol and wherein the UV absorber is 2,2'-methylenebis(6-(2H-benzotriazol-2-yl)-4-1,1,3,3-tetramethylbutyl)phenol) and/or 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methyl phenol; during said injecting, moving said two facing mold inserts toward one another at a speed of less than 150 mm/s and at a pressure of not more than 4788 kPa to define a final molding cavity whose volume is less than that of said initial molding cavity; and after cooling and opening of the molding cavity, recovering the weld line free minus power lens element; wherein one of said two facing mold inserts comprises a flat surface facing the initial molding cavity, thereby to form a flat surface on one side of the weld line free minus power lens element, wherein the other of said two facing mold inserts comprises a convex surface facing the initial molding cavity, thereby to form a concave surface on an opposite side of the weld line free minus power lens element, wherein the center distance between said two facing mold inserts when delimiting said initial molding cavity is not more than five times a center thickness of the weld line free minus power lens element, and wherein each of said two facing mold inserts is formed at least in part of borosilicate crown glass, so as to obtain a wafer having a diameter in a range from 55-85 mm and a weld line free minus power lens element that has a power profile within the range of ± 0.06 diopter and a warpage of the flat surface of the weld line free minus power lens element that is within ± 0.06 diopter injecting a melt of thermoplastic material comprising at least one UV absorber at a temperature higher than a glass transition temperature (Tg) of the thermoplastic material and at a speed of not more than 25 mm/s in an initial molding cavity delimited by two facing mold inserts, wherein the thermoplastic material is polycarbonate with a weight average molecular weight of less than 26,000 g/mol and wherein the UV absorber is 2,2'-methylenebis(6-(2H-benzotriazol-2-yl)-4-1,1,3,3-tetramethylbutyl)phenol) and/or 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methyl phenol; during said injecting, moving said two facing mold inserts toward one another at a speed of less than 150 mm/s and at a pressure of not more than 4788 kPa to define a final molding cavity whose volume is less than that of said initial molding cavity; and after cooling and opening of the molding cavity, recovering the weld line free minus power lens element; wherein one of said two facing mold inserts comprises a flat surface facing the initial molding cavity, thereby to form a flat surface on one side of the weld line free minus power lens element, wherein the other of said two facing mold inserts comprises a convex surface facing the initial molding cavity, thereby to form a concave surface on an opposite side of the weld line free minus power lens element, wherein the center distance between said two facing mold inserts when delimiting said initial molding cavity is not more than five times a center thickness of the weld line free minus power lens element, and wherein each of said two facing mold inserts is formed at least in part of borosilicate crown glass, so as to obtain a wafer having a diameter in a range from 55-85 mm and a weld line free minus power lens element that has a power profile within the range of ± 0.06 diopter and a warpage of the flat surface of the weld line free minus power lens element that is within ± 0.06 diopter