Amputees often feel eerie sensations from their missing limbs. These "phantom limb" feelings can include pain, itching, tingling, or even a sense of trying to pick something up. Patients who lose an eye may have similar symptoms—with the addition of actual phantoms. Phantom eye syndrome (PES) had been studied in the past, but University of Liverpool psychologist Laura Hope-Stone and her colleagues recently conducted the largest study of PES specifically in patients who'd lost an eye to cancer. The researchers sent surveys to 239 patients who'd been treated for uveal melanoma at the Liverpool Ocular Oncology Centre. All of these patients had had one eye surgically removed. Some of their surgeries were only 4 months in the past; others had taken place almost 4 and a half years earlier. Three-quarters of the patients returned the surveys, sharing details about how they were doing in their new monocular lives.Sixty percent of respondents said they had symptoms of phantom eye syndrome. These symptoms included pain, visual sensations, or the impression of actually seeing with the missing eye. Patients with visual symptoms most often saw simple shapes and colors. But some people reported more distinct images, "for example, resembling wallpaper, a kaleidoscope, or fireworks, or even specific scenes and people," the authors write. Then there were the ghosts. Some people said they had seen strangers haunting their fields of vision, as in these survey responses:

PES patients describe the ghostly images they see with their missing eyes. A survey isn't a perfect way to measure how common PES is overall. But Hope-Stone says there were enough survey responses to produce helpful data for doctors who treat patients with eye cancer. "We can now tell whether certain kinds of patients are more likely to have phantom symptoms," she says. For example, "PES is more common in younger patients, and having pain in the non-existent eye is more likely in patients who are anxious and depressed, although we don’t know why." About a fifth of PES patients, understandably, said they were disturbed by their symptoms. A similar number found them "pleasurable," Hope-Stone says. Doctors aren't sure exactly why phantom eye syndrome occurs. Since different patients have different symptoms, Hope-Stone says, "I suspect that...there may be a range of causes." For that matter, phantom limbs are still mysterious to doctors too. "Human perception is a complex process," Hope-Stone explains. Even when our sensory organs are gone—the vision receptors in our eyes, the pain and touch receptors in our hands—the nerves and brain areas that used to talk to those organs keep working just fine. "Interactions between [these systems] may contribute to phantom sensations," she says, although "the exact mechanisms are unclear." Even if they don't know why it happens, doctors can warn their patients about the kinds of symptoms they're likely to experience—and the ghosts they might see.

Image: by sarcaser (via Flickr)

Hope-Stone L, Brown SL, Heimann H, Damato B, & Salmon P (2015). Phantom Eye Syndrome: Patient Experiences after Enucleation for Uveal Melanoma. Ophthalmology PMID: 26004080