Disembodied spirits phasing into this reality do receive photon light emissions from our environment as they themselves emit electromagnetic radiation. Their consciousness interacts with incoming electromagnetic waves of light and translates them into equivalent objects they were familiar with in their life. Basically ghosts take the middle man, aka the human eye, out of the equation. Their metaphysical mind does all the work. Naturally the biological brain that ultimately interfaces with the human soul is removed from the sight formula as well. However the bombardment of so many electromagnetic waves can be disorienting, and takes some time to decipher for a new ghost. In addition our world will never look the same as it did through biological human eyes.
In addition their sight can be called surround sight since the photon emissions are coming at them from every angle. They view the physical world in a 360 degree holographic manner rather than from one narrow 3-D two eye perspective. In other words if a ghost appears you have no hope of sneaking up behind it. It saw you the minute you entered the room. As four dimensional beings they also have 4-D vision which means they can see through your body, walls, or any other physical obstruction. If they are strong willed they will soon realize they can see through time as well straight into the past, and future.