An image sensor with an array of image sensor pixels is provided. Each pixel may include a photodiode and associated pixel circuits formed in a semiconductor substrate. Buried light shields may be formed on the substrate to present pixel circuitry that is formed in the substrate between two adjacent photodiodes from being exposed to incoming light. Metal interconnect muting structures may be formed over the buried light shields. In one embodiment, light blocking structures may be formed to completely seal the interconnect routing structures. The light blocking structures may be formed on top of the buried light shields or on the surface of the substrate. In another embodiment, planar light blocking structures that are parallel to the surface of the substrate may be formed between metal routing layers to help absorb stray light. Light blocking structures formed in these ways can help reduce optical crosstalk and enhance global shutter efficiency.