Flicker fusion frequency in amblyopia ex anopsia.
نویسنده
چکیده
Amblyopia ex anopsia is characterized by a defect in visual acuity of one eye, beginning in infancy, often with strabismus. The amblyopia disappears upon occlusion of the dominant eye in children, but not readily in adults. Peripheral acuity and sensation remain normal in field and threshold studies. It is believed that the origin of the amblyopia is in the macular projection of the visual cortex, and that the lesion is of the nature of a suppression or a conditioned reflex. Although visual acuity is defective, other visual sensations in the central retina appear to be normal. This may limit the lesion more definitely to the cortical layers involved in form vision, preserving the more primitive levels, namely, those for light or brightness contrast, dark-adaptation thresholds, color thresholds, and the capacity of the eye to fixate and localize accurately small points of light on the fovea. Wald and Burian suggested that these layers might be outside the cortex, since in monkeys only pattern vision is lost after cortex ablation. Visual acuity tests, as performed in the office, test pattern vision. Visual field tests with small targets and good illumination are chiefly tests of pattern vision. When targets are made larger and less contrasting to the background, or if the illumination is reduced, a different sensation, brightness contrast, is being stimulated. Experiments on the "central" retina in amblyopia may not be exactly central. Wald and Burian found that the amblyopic «ye was slightly less capable of centering on a 1-degree target than the dominant eye, and that the threshold curves showed the effect of rod stimulation, although supposedly only
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Centrally fixed flicker thresholds in amblyopia.
Theories as to the etiology of amblyopia (also called amblyopia ex anopsia, strabis mus amblyopia, and amblyopia without ophthalmoscopic signs) may roughly be divided into two groups depending upon whether the primary defect is postulated in the cere bral cortex or in the retina. Wald and Burian who are among the most lucid ad vocates of the former position described measurements on five cas...
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A Preliminary Report of the More Recent Methods of Treatment of Amblyopia, Especially When Associated with Eccentric Fixation
DURING the last two centuries the treatment of amblyopia ex anopsia in cases of strabismus has made considerable progress. One of the earliest forms of treatment was occlusion of the fixing eye. This was first carried out by Buffon (1743), who also showed the need for correction of the refractive error by means of spectacles. More than a century later, Javal (1896) thought that squint was prima...
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عنوان ژورنال:
- American journal of ophthalmology
دوره 32 Pt. 2 6 شماره
صفحات -
تاریخ انتشار 1949