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The Clinical Significance of Fixation Disparity in Binocular Vision

出版	University of Bradford, 1988
URL	http://books.google.com.hk/books?id=mjEanQEACAAJ&hl=&source=gbs_api

註釋It has been shown that fixation disparity can be produced by prism stress, and it has therefore been suggested that its presence constitutes a sign of stress on binocular vision. Fixation disparity can be present in the absence of any stress, and therefore may be a physiological condition. This study explores the effect of more realistic types of stress, other than those caused by prisms and lenses, on fixation disparity and associated 'phoria. The types of stress included are reading in inadequate illumination, reading at an abnormally close working distance and carrying out normal close work tasks during a working day. It was found that such stresses increased the magnitudes of fixation disparity and associated 'phoria which were accompanied by increasing visual symptoms. It is confirmed that the correlation between heterophoria and fixation disparity' is not very high. A strong relationship was noted between fixation disparity and associated 'phoria. It was found that visual symptoms are more related to fixation disparity or associated 'phoria than heterophoria. This study also explored the importance of a central fusion lock in instrument design. The presence of a central lock subjectively reduced the oscillating movements of the nonius lines. The shapes and the central slopes of the forced vergence fixation disparity curves were not affected by the presence or absence of a central binocular lock.