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Light spot patterns testing the central 24 degrees or 30 degrees of the visual field, are most commonly used. Most perimeters are also capable of testing up to 80 or 90 or even 120 degrees. Another method is for the practitioner to hold up one, two, or five fingers in the four quadrants and center of a patient's visual field (with the other eye ...
Humans have a slightly over 210-degree forward-facing horizontal arc of their visual field (i.e. without eye movements), [4] [5] [6] (with eye movements included it is slightly larger, as you can try for yourself by wiggling a finger on the side), while some birds have a complete or nearly complete 360-degree visual field. The vertical range of ...
The polar angle is considered to be zero degrees when a locus is horizontally to the right of the fixation point and to increase to a maximum of 360 degrees going anticlockwise. Distance from the origin is given in degrees of visual angle; it's a measure of eccentricity. Each polar axis is a meridian of the visual field. For example, the ...
Visual angle is the angle a viewed object subtends at the eye, usually stated in degrees of arc. It also is called the object's angular size . The diagram on the right shows an observer's eye looking at a frontal extent (the vertical arrow) that has a linear size S {\displaystyle S} , located in the distance D {\displaystyle D} from point O ...
An eye that is accompanied by a limitation in the fields of vision such that the widest diameter of the visual field subtends an angle no greater than 20 degrees shall be considered for purposes in this paragraph as having a central visual acuity of 20/200 or less.
At the low end of the range is the absolute threshold of vision for a steady light across a wide field of view, about 10 −6 cd/m 2 (0.000001 candela per square meter). [23] [24] The upper end of the range is given in terms of normal visual performance as 10 8 cd/m 2 (100,000,000 or one hundred million candelas per square meter). [25]
Classical image of the shape and size of the visual field [28]. The outer boundaries of peripheral vision correspond to the boundaries of the visual field as a whole. For a single eye, the extent of the visual field can be (roughly) defined in terms of four angles, each measured from the fixation point, i.e., the point at which one's gaze is directed.
The visual field index (VFI) reflects retinal ganglion cell loss and function, as a percentage, with central points weighted more. [ 21 ] It is expressed as a percentage of visual function; with 100% being a perfect age-adjusted visual field and 0% represents a perimetrically blind field.