You will need a QuickTime plug-in (available free from Apple) to display the movies. Links to the videos in Microsoft AVI format are below
Homonymous hemianopia, the loss of vision in about half the visual field (i.e. on one side and in both eyes), can occur due to stroke, head injury, or surgery to remove tumors. Hemianopic visual field loss causes a range of problems, the most common being mobility and navigation. Patients with hemianopia frequently complain of bumping into obstacles on the side of the field loss, often causing bruised arms and legs. The number of such incidents may decrease with adaptation to the condition, presumably because patients become more cautious and learn to use head and eye scanning techniques to avoid collisions. Despite such improvements in function, many patients continue to suffer from the effects of the limited visual field. Currently we are investigating the utility of novel prism glasses that expand the visual field of patients suffering from hemianopia. For a more detailed explanation please see:
Peli E, Treating Hemianopia Using Prisms to Create Peripheral Diplopia
(1999) Vision '99 The International Conference on Low Vision. In press.
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Here are some simple videos that simulate the vision of patients afflicted with hemianopia. The first video depicts vision without the aid of the prism glasses while the second depicts vision with the aid of the prism glasses.
You will need a QuickTime plug-in (available free from Apple) to display the movies. Links to the videos in Microsoft AVI format are below
This simulation demonstrates the vision of a patient with left homonymous hemianopia scanning a visual scene. To experience vision as would a person with hemianopia, you should look (i.e. fixate) directly at the green dot. The shaded gray area to the left of the fixation point represents the area of visual field loss. The arrow illustrates the direction of eye movements as the person scans across the visual the scene. Note that for simplicity, the scene is static (i.e. the people are not moving).
This simulation demonstrates the vision of a patient with left homonymous hemianopia scanning a visual scene with the aid of the prism glasses. Both upper and lower prism segments are used. To experience vision as would a person with hemianopia, you should look (i.e. fixate) directly at the green dot. The shaded gray area to the left of the fixation point represents the area of visual field loss. The arrow illustrates the direction of eye movements as the person scans across the visual the scene. Note that for simplicity, the scene is static (i.e. the people are not moving). The prism glasses brings into view items that would otherwise not be seen. Also notice that with the prism the instantaneous field of view is wider than it is without the prism. Notice the chromatic fringes on the spatially distorted ghost images created by the prisms. These artifacts provide the patient with needed indications regarding the source of the images and support adap tation and correct spatial localization.
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