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The macula corresponds to the central 17 degrees diameter of the visual field; the fovea to the central 5.2 degrees, and the foveola to 1–1.2 degrees diameter. [ 10 ] [ 11 ] [ 12 ] Note that in the clinical literature the fovea can refer to the central 1–1.2 deg, i.e. what is otherwise known as the foveola, and can be referred to as the ...
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.
Amsler grid, Chart 1. There are 7 types of Amsler grid charts. All charts measure 10 cm × 10 cm (3.9 in × 3.9 in), which when viewed at a distance of 33 cm (13 in) from the eye can be used to measure defects in the central 20 degrees of the visual field. [3]
The visual acuity is assigned in the form of a fraction. Visual acuity is recorded as "20/20" (or another fraction like 20/40) when all optotypes (letters or symbols) on a specific line of the eye chart are correctly identified. When an individual correctly identifies additional 2 letters in the next 20/30 lines, then they will be assigned 20/40+2.
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 ...
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 ...
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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.