Strong modulation of face distortions in prosopometamorphopsia by color

Prosopometamorphopsia (PMO) is a rare perceptual condition in which people see distortions to faces. Individuals with PMO often find the distortions disturbing, so developing interventions that reduce them would be valuable. Here, we report the case of VS, a 58-year-old man with full-face PMO who sees remarkably similar distortions on every face he encounters in daily life. These distortions include severely stretched eyes, ears, and mouths, widened noses, three deep grooves on the cheeks, two on the forehead, and one shallow groove on the chin. Two characteristics of VS’s case make his PMO unique: he does not see distortions on normally colored faces on screens or paper, and his distortions are strongly modulated by color. To visualize his distortions, we asked VS to compare simultaneously presented real-world faces and photos of them taken under the same conditions. Using image editing software and VS’s real-time feedback, we produced the first photorealistic visualizations of PMO distortions. To measure the effect of color on his distortions, VS described and rated, on a scale from zero (“no distortion”) to 10 (“maximum distortion”), what he saw when looking at real-world stimuli with and without Roscolux colored plastic filters in front of his eyes. The intensity and nature of the face distortions were not affected by view (frontal, profile), orientation (0º, 90º, 180º, 270º), or the proportion of the face visible. Distortions were strongly and consistently affected, however, by color, with green filters decreasing (median = 1.50) and red filters increasing (median = 7.00) the distortions relative to the no-filter baseline (median = 5.00). Aside from paragraphs and grid patterns, no other stimuli were perceived as distorted. The results demonstrate that color filters can substantially reduce face distortions in PMO and suggest that color may play a role in the conscious perception of face shape.