April 5, 2024 – For more than two years a 58-year-old man has seen “demonic”-looking human faces whenever he looks at another person.
Now, researchers have for the first time used computer software to depict accurate representations of the facial distortions that patients like this see thanks to a rare visual disorder called prosopometamorphopsia, or PMO, which is often mistaken for mental illness.
PMO is a rare, often misdiagnosed, visual disorder in which human faces appear distorted in shape, texture, position, or color. Most patients with PMO see these distorted facial features all the time, whether they are looking at an actual person, on a screen, or paper.
But the man involved in this new study published in March, said he only sees the distortions only when encountering someone in person but not on a screen or on paper.
This allowed researchers to use editing software to create an image on a computer screen that matched the patient's distorted view.
"This new information should help healthcare professionals grasp the intensity of facial distortions experienced by people with PMO," study investigator Brad Duchaine, PhD, professo in the Department of Psychological and Brain Sciences at Dartmouth College in Hanover, NH, said.
"A substantial number of people we have worked with have been misdiagnosed, often with schizophrenia or some sort of psychotic episode, and some have been put on antipsychotics despite the fact they've just had some little tweak in their visual system," he said.
Prevalence Underestimated?
Although fewer than 100 cases of PMO have been reported in the literature, Duchaine said this is likely an underestimate. Based on a response to a website his team created to recruit affected patients, he said he believes "there are far more cases out there that we realize."
PMO might be caused by a neurologic event that leads to a lesion in the right temporal lobe, near areas of facial processing, but in many cases, the cause is unclear.
PMO can occur in the context of head trauma, as well as stroke, epilepsy, migraine, and hallucinogen-persisting perception disorder, researchers noted. The condition can also occur without detectable structural brain changes.
"We're hearing from a lot of people through our website who haven't had, or aren't aware of having had, a neurologic event that coincided with the onset of face distortions," Duchaine noted.
The patient in this study had a significant head injury at age 43 that led to hospitalization. He was exposed to high levels of carbon monoxide about 4 months before his symptoms began, but it's not clear if the exposure is related to his PMO.
He was not prescribed any medications and reported no history of illegal drug use.
The patient also had a history of bipolar affective disorder and posttraumatic stress disorder. While he sees visions of distorted faces, he did not have delusional beliefs about the people he encountered, the investigators wrote.
Neuropsychological tests were normal, and there were no problems with his eye sight. Computer-based face perception tests showed mild problems in recognition of facial identity but normal recognition of facial expression.
The patient did not typically see distortions when looking at objects, such as a coffee mug or computer. However, said Duchaine, "if you get enough text together, the text will start to swirl for him."
Eye-Opening Findings
The patient described the visual facial distortions as "severely stretched features, with deep grooves on the forehead, cheeks, and chin." Even though these faces were distorted, he was able to recognize the people he saw.
Because the patient reported no distortion when viewing facial images on a screen, researchers asked him to compare what he saw when he looked at the face of a person in the room to a photograph of the same person on a computer screen.
The patient alternated between looking at the actual person, which he perceived as distorted, and the photo on the screen, which he perceived as normal.
Researchers used real-time feedback from the patient and photo-editing software to manipulate the photo on the screen until the photo and the patient's visual perception of the person in the room matched.
"This is the first time we have actually been able to have a visualization where we are really confident that that's what someone with PMO is experiencing," said Duchaine. "If he were a typical PMO case, he would look at the face in real life and look at the face on the screen and the face on the screen would be distorting as well."
The researchers discovered that the patient's distortions are influenced by color; if he looks at faces through a red filter, the distortions are greatly intensified, but if he looks at them through a green filter, the distortions are greatly reduced. He now wears green-filtered glasses in certain situations.
Duchaine hopes this case will open the eyes of clinicians. "These sorts of visual distortions that your patient is telling you about are probably real, and they're not a sign of broader mental illness; it's a problem limited to the visual system," he said.
