Patent ID: 8535114

Claim:
A method for manufacturing a precursor lens for a rim-shaped lens, the precursor lens having a circular or elliptical external shape, the precursor lens being processed into a rim-shaped lens by cutting off a peripheral edge thereof so as to be fitted in a predetermined spectacle rim, the precursor lens being provided with rotationally asymmetric lens characteristics corresponding to a prescription of a user, the method comprising: a processing data input step of inputting data to specify at least a shape of the rim-shaped lens, and a precursor lens manufacturing step of manufacturing the precursor lens by processing a material block by a processing means based on processing data of the rim-shaped lens, wherein an upper borderline and a lower borderline are imaginarily set to be extended in a rightward/leftward direction with a predetermined interval therebetween in an upper part and a lower part, respectively, of a rim shape of the rim-shaped lens, wherein processing is performed while reflecting the processing data until the upper and lower borderlines are reached, and wherein parts outside the upper and lower borderlines are processed while correcting the processing data so that an edge thickness of the manufactured precursor lens securely becomes larger than a predetermined thickness.