Visual functions in a patient with acquired achromatopsia

We describe an investigation of visual responses in a patient, whose MRI brain scans reveal bilateral lesions affecting the fusiform and lingual gyri. Subjectively, he reports that colours appear abnormal to him and his descriptions of surface colours are similar to those of other patients who suffer cerebral achromatopsia. His colour matching and two colour increment threshold data establish that his cone photoreceptors have normal spectral responses, and his spectral sensitivity measured against a white background exhibits normal colour-opponent characteristics. His colour discriminations are, however, impaired but other visual response characteristics, including lightness discrimination, velocity discrimination, stereoscopic fusion and binocular rivalry are normal. He does, however, suffer from two neurological conditions, prosopagnosia and topographical agnosia, commonly found in association with cerebral achromatopsia.