Field of view
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Your field of view is that part of the observable world that you are able to see at any given moment.
Different animals have different fields of view, depending on the placement of the eyes. Humans have a 180-degree forward-facing field of view, while some birds have a complete 360-degree field of view. In addition the vertical range of the field of view may vary.
The range of visual abilities is not uniform across a field of view, and varies from animal to animal. For example, binocular vision, which is important for depth perception, only covers 140 degrees of the field of vision in humans; the remaining peripheral 40 degrees have no binocular vision (because of the lack of overlap in the images from either eye for those parts of the field of view). The afore-mentioned birds would have a scant 10 or 20 degrees of binocular vision.
Similarly, color vision and the ability to perceive shape and motion vary across the field of view; in humans the former is concentrated in the center of the visual field, while the latter tends to be much stronger in the periphery. This is due to the much higher concentration of color-sensitive cone cells in the macula, the central region of the retina, as compared to the higher concentration of motion-sensitive rod cells in the periphery. Since cone cells require considerably brighter light sources to be activated, the result of this distribution is that peripheral vision is relatively much stronger at night.
Visual fields
Different neurological difficulties cause characteristic forms of visual disturbances. Some are illustrated below. In humans these and other types of visual field loss based in the eye, optic nerve or brain are measured with confrontational testing using objects in various parts of the field of view and perimetry.
Missing image Fullvf.png Paris as seen with full visual fields |
Missing image Bitempvf.png Paris as seen with bitemporal hemianopsia |
Missing image Binasalvf.png Paris as seen with binasal hemianopsia |
Missing image Lhvf.png Paris as seen with left homonymous hemianopsia |
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