1. A method comprising steps of: (a) receiving as input an optical proximity corrected mask design for an integrated circuit; (b) searching the corrected mask design to find a critical edge of a polygon that is closer than a selected minimum distance from a polygon edge opposite the critical edge; (c) constructing a critical region bounded by the critical edge and the polygon edge opposite the critical edge; (d) comparing the critical region to a potential defect criterion; and (e) generating as output a location of the critical region when the critical region satisfies the potential defect criterion.