This study investigates the effect of local microscopic constraints on the shrinkage distribution in injection molded product. Flat specimens with and without microstructures were injection molded, and the distribution of in-plane shrinkage was measured using an optical method. An array of point marks was imprinted on the mold surface, which enables the optical measurement of the shrinkage distribution. When microstructures were applied on the specimen surface, the shrinkage is found to be reduced significantly near the microstructures. As discussed previously by other researchers, this would be due to the constraining effect of microstructures, which limit the lateral motion in the mold cavity during the cooling stage. In addition, the effect of packing pressure is studied by observing more details of the shrinkage away from the gate. It was observed that both the magnitude and the anisotropy of the shrinkage tend to decrease as the packing pressure increases. However, when microstructures are applied, such effect of the packing pressure is less visible since the shrinkage level is already at the minimum range.