Investigation of visual acuity in conditions of disturbance in mentally healthy people and patients with schizophrenia

Purpose. To approve and propose a method of estimation of visual functions in psychopathology, to receive additional signs of increase in the level of internal noise in schizophrenia with its help. Material and methods: There were examined 41 conditionally mentally healthy examinees and 56 patients of Krasnoyarsk regional psychoneurological clinic with the diagnosis of paranoid schizophrenia. There was registered probability of the right answer during presentation of optotypes without noise and with imposing noise of different quality and quantity. There was used fixed noise, in which the size of elementary disturbance made 4*4 pixels, and percentage, in which the size of elementary disturbance was equaled 25 % of the size of Landolt's ring break. The follow-up was carried out binocularly. Visual acuity of all examinees was nor?mal or corrected up to norm. Results. The most expressed reduction in noise stability in the patients, suffering from schizophrenia, in comparison with the controls, is recorded in presentation of optotypes with imposing 30 % of the noise level with the size of elementary distur?bance 25 % of size of Landolt's ring break. Conclusion. Results of the carried out study allow to make a conclusion of increase of the level of internal noise and accordingly of reduction in noise stability in schizophrenia. Both in the norm and in schizophrenia imposing of stimulus of 30 % and 40 % of disturbance on the image leads to reliable reduction in correct?ness of answers, accordingly to visual acuity in recognition of the site of Landolt's ring break. In increase in the external disturbance up to 40 % external noise is im- posed on the internal one, the signal is muffled and recognition becomes difficult.That is internal noise is fundamental restriction of perception.