Download - Visual field
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VISUAL FIELD
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OVisual field testing is most often performed on glaucoma patients.
OGlaucoma affects the peripheral vision before central vision
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OCentral vision:- O located in a small area of the retina
called the macula. O Cones cells are helping in seeing detail
in color and in relatively bright lightO Rest of the retina contains rod cells
which do not see detail.
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OPeripheral vision :- O Make us aware of the location of
objects in visual spaceO Directs central vision toward a
particular object if desired
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O Division of Labour - Central FieldO highly developed area of the retina
responsible for detailed vision,O read, recognise faces, detect colours.
O Peripheral FieldO specialised in the detection of motion
signals,O enables safe navigation around our
environment.
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Visual field testing
OA method by which measure the extent of visual space and sensitivity to it at any given moment
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OBy increasing the intensity of a stimulus to a known area of the retina until the stimulus is seen
OTwo basic types of stimulus presentation: O Static perimetryO Kinetic perimetry
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STATIC PERIMETRY
O The presentation of stimuli to one spot of the retina in increasing levels of intensity until the stimulus is seen
O Time consuming
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O The Goldmann perimeter
O Automated perimeters
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KINETIC PERIMETRY
OPresents moving stimulus of a particular size and intensity
OThe stimulus is moved from a non-seeing area toward the fixation point until it is seen.
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O A boundary is mapped for the particular stimulus size and intensity
O The size and/or intensity of the stimulus is then changed and another boundary is mapped
O Viewed together on a chart, these boundaries give a picture of the overall extent of the visual field
O Give a measure of the sensitivity of the visual field,
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Goldman perimeter
O Light stimulus is moved from outside of bowl towards the centre.
O Manually operated.O Light source can be varied in size and brightness.O Start with I4E brightest and smallest lightO And then reduced brightness of target to I3E and
then I4E – checking sensitivityO If peripheral field reduced – increase size of
target III4E until using the largest target V4EO Result is isopters
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