Furthermore, reading ability may be considerably limited by a hemianopsia or a larger defect of the horizontal visual field, especially to the right side. Pronounced visual field defects render the exploration of the environment difficult, with corresponding consequences for daily work procedures. Visual field defects represent a serious handicap for the affected patients. The requirement to explore the matrix on a row-by-row or column-by-column basis permits testing of the ability to shift the required search strategy, which can be impaired, for example, in the case of frontal brain damage. One reaction key is used for the answer ""present"" and another for the answer ""not present"". In this task, a matrix-like arrangement of 5 x 5 stimuli is used, the aim being to detect whether this arrangement includes a critical stimulus or not. Equally diverse are the causes of a deficit in exploring the environment after brain damage, which in many cases presents an obvious handicap in daily life. It is a complex process for which the intention and prior knowledge of the individual, the ability to plan ahead, an unrestricted visual field, the ability to shift visual attentional focus, and unimpaired eye movements are important. The exploration of the visual environment is one of the most basic abilities subserving the safe movement in space, the search for an object, when regarding an object or picture, or in monitoring and controlling a traffic situation.
The task is administered under two conditions: a "gap" and an "overlap" condition. The subject should respond as quickly as possible by pressing the key as soon as this critical stimulus appears. A critical stimulus appears centrally at irregular intervals. Either a critical or a neutral stimulus is presented to the left or right of a fixation stimulus (an "S" lying on its side) in pseudorandom sequence. In this task, the latency of saccadic eye movement to the left or to the right is assessed in a reaction task. In rehabilitation a deficit in saccadic eye movements can render compensation training of a visual field defect considerably more difficult.
Impaired eye movement can represent a major handicap in road traffic and may result in impaired reading ability, especially when there is a right-sided manifestation. This is a central function, on the basis of which we explore our surroundings and are able to orient ourselves in a given situation. One of the most efficient forms of focusing is to look at something, that is, to change the direction of gaze and fixating on relevant information in the environment.
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