Grooves are formed in the inner surface of two rims, and a part of the inner side of each of the grooves is formed as a cutout section. Lenses are removed from the rims while avoiding the interference between a stopper member, which is pivotably provided to a bridge, and inner regions of the rims by pivoting downward the stopper member. Then, new lenses are inserted through the inner regions. After that, the stopper member is rotated upward and fixed to the bridge. As a result, the stopper member interferes with the inner regions of each of the rims to firmly fix the lenses within the rims.
