Edgaras Diržius1,2,3, Viktorija Mickevičiūtė4, Emilija Padervinskytė4, Darius Leskauskas1, Aleksandr Bulatov2
1Lithuanian University of Health Sciences, Psychiatric Clinic, Kaunas, Lithuania
2Lithuanian University of Health Sciences, Institute of Biology Systems and Genetics, Kaunas, Lithuania
3Lithuanian University of Health Sciences, Center for Evidence Based Medicine, Kaunas, Lithuania
4Lithuanian University of Health Sciences Medical Faculty, Kaunas, Lithuania
Introduction: Various studies have reported differences in early visual processing, gain control and integration for patients with schizophrenia spectrum disorders (SSD). We investigated Müller-Lyer (ML) and Oppel-Kundt (OK) illusions to get insight in visual cognitive functions for patients with SSD.
Aim: To investigate the ML and OK illusions manifestation among the people with SSD.
Material and methods: in the prospective study were included 19 patients, diagnosed with SSD and matched comparison group (CG) without any mental, neurological diseases or visual impairment. Stimuli used in experiments consisted of three pairs of the ML wings arranged according to the Brentano pattern and OK figures of white spots presented horizontally against a black background. Using computerized equipment 40 ML stimuli were presented in monitor with various sizes (from 10° to 350°) of the inner corners. Subject’s task was to place the central part of the figure in the middle between the outer ones. In OK figures the subjects were asked to adjust the unfilled part of the stimulus to be equal in length to the referential one. The number of the filling spots in the referential interval varied from 0 to 19. Participants repeated ML and OK experiments for 10 time.
Results: When comparing SSD group with CG for OK we found statistically significant difference when zero or one point were in referential line. For ML figures differences were found for 12 corner values. Patients tended to make larger mistakes for corners <90° and >330°.
Conclusions: Although we found that patients with SSD tended to make smaller mistakes when evaluating OK figures with no illusionary effect and larger susceptibility when one point is involved, but without any manifestation differences with 2 to 19 dots in referential line. For ML figures patients tended to make larger mistakes for more acute and obtuse corners.