We present a method for manipulating individual sites in a 2-D optical lattice that enables the creation of defects within otherwise periodic light patterns. The modified optical lattice is created by interference of plane waves and spiral phase waves. Spiral phase modulation creates an optical vortex that is well suited for addressing single rows of the optical lattice owing to the localized wrap of the phase front. Local fringes can be split, annihilated, or have their size tuned by controlling the charge and location of the vortex cores. These properties provide a connection between dislocations in crystals, waves, and optical lattices.