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E.O. Roberts, F.A. Proudlock, I. Gottlob, M. Reveley; Eye Movements in Schizophrenia and Reading . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2924.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Smooth pursuit and saccadic eye movements are known to be abnormal in schizophrenics. We have previously shown that there are also reading abnormalities; schizophrenics fixate on many more letters and have smaller saccades. We aimed to determine possible mechanisms by which these reading abnormalities occur; abnormalities involving the parafoveal region may be responsible, this was investigated using moving window technique. Methods:11 schizophrenic patients and 12 healthy, age, sex and National Adult Reading Test (NART) matched controls were asked to perform a reading task while using the moving window technique (letters outside the window masked using Xs, spaces and letter size were preserved). Simple text was projected onto a rear projection screen and presented to the subjects, good calibration and drift correction were essential to ensure the moving window would be located precisely where the subjects were looking. Eye movement recordings were carried out using an infrared pupil tracker (Eye Link Sensomotoric Instruments, GmbH, Germany). Subjects asked to read ten pages of text; the size of the window was changed for each page (thus changing the amount of parafoveal information available). The number of letters shown left of fixation was fixed at three and the number of letters shown randomly (twice) to the right of fixation were 2, 4, 8 and 16; a page showing the complete text was also shown (no window present). We looked at the reading velocities of each window size for both groups. Results:We found that the control group had higher reading velocities overall than the schizophrenic group and that there was a significant difference (p = 9x10–7) between the reading velocities with decreasing window sizes for the controls. When shown fewer parafoveal letters to the right controls had a slower reading velocity than when the whole text was shown to them. In contrast we found no significant difference between the reading velocities in the schizophrenics group with decreasing window size (p = 0.2). Conclusions:In normal subjects reduction of parafoveal information reduces reading velocities. However if parafoveal information is disrupted in schizophrenic subjects there is no significant change in reading velocities. A possible explanation is decreased working memory in schizophrenia or inability to suppress fixation of letters.
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