visual field

VISUAL FIELD

OVisual field testing is most often performed on glaucoma patients.

OGlaucoma affects the peripheral vision before central vision

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.

OPeripheral vision :- O Make us aware of the location of

objects in visual spaceO Directs central vision toward a

particular object if desired

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.

Visual field testing

OA method by which measure the extent of visual space and sensitivity to it at any given moment

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

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

O The Goldmann perimeter

O Automated perimeters

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. 

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,

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