We recorded contrast sensitivity in normal and schizophrenic patients. We presented Gabor gratings with sinusoidal distribution of brightness, with the spatial frequency: 0.4 cycles/degree, 3.6 and 17.9 cycles/degree. Taken together patients with schizophrenia compared to the healthy subjects showed a decline of contrast sensitivity at low and medium spatial frequencies. We measured the influence of duration of illness and type of treatment on contrast sensitivity. Patients with schizophrenia less than 10 years, showed a decrease of contrast sensitivity only at low spatial frequencies, while patients suffered with schizophrenia for more than 10 years--at low, medium and high spatial frequencies. Persons with schizophrenia less than 10 years receiving treatment with atypical antipsychotics, show a decrease in contrast sensitivity at low spatial frequencies, while treated with typical antipsychotics--in the low and high spatial frequencies.