Thallium intoxication is characterized by the development of painful peripheral neuropathy, alopecia, mental disorders, and in severe cases, respiratory failure and death. Toxic optic neuropathy is also a feature. Ophthalmologic features of thallium poisoning include optic neuropathy, blepharoptosis, lens opacities, and ophthalmoplegia. A 44-year-old man with criminal sublethal thallium poisoning was examined one month after he was seen in the neurology department with classic systemic features. He was found to have diminished contrast sensitivity, a tritan defect in color vision, and a relative cecocentral scotoma before he developed optic atrophy.