After refractive surgeries like LASIK, LASEK, and PRK, some patients report seeing multiple images, sometimes called "shadows" or "ghosts". The technical term is "monocular polyopia," which literally means "one eye, many images." Some patients see only a single additional ghost (monocular diplopia), whereas others see too many to count. Some patient's ghost images are relatively transparent, whereas others are so opaque that it becomes impossible to discern which is the ghost and which is "real image."
Ghosting is more commonly seen at night, but it may occur in all lighting situations. Ghosting may be a result of induced astigmatism, decentered ablation, or large pupils. Patients with large pupils have a multi-focal cornea at night when the pupil dilates, allowing light to pass through both the treated and untreated areas of the cornea.
Some images courtesy VisionSimulations.com