Detects dysfunction in central and peripheral vision which may be caused by medical conditions such as glaucoma, pituitary disease, stroke, brain tumors or other neurological deficits.
Perimetry testing is important in the screening, diagnosing, and monitoring of various eye, retinal, optic nerve and brain disorders.
Performed clinically by keeping the patient’s gaze fixed while presenting objects at various places within their visual field.
Tangent screen
Automated perimetry uses a mobile stimulus moved by a perimetry machine.
The patient indicates whether he sees the light by pushing a button.
It uses a white background and lights of incremental brightness.
The simplest form of perimetry uses a white tangent screen.
White-on-white perimetry is commonly used for early detection of blind spots.
Vision is tested by presenting different sized pins attached to a black wand, which may be moved, against a black background.
The simplest form of perimetry uses a white tangent screen.
This type of perimetry is the most commonly used in clinical practice.
The sensitivity of white-on-white perimetry is low, and the variability is relatively high; as many as 25–50 percent of the photoreceptor cells may be lost before changes in visual field acuity are detected.
Vision is tested by presenting different sized pins attached to a black wand, which may be moved, against a black background.
A computer then shines lights on the inside dome and the patient clicks the button whenever a light is seen, and the computer maps and calculates the patient’s visual field.
The exam may be performed by a technician in one of several ways.
The test may be performed by a technician directly, with the assistance of a machine, or completely by an automated machine.
Machine-based tests aid diagnostics by allowing a detailed printout of the patient’s visual field.
Specialized equipment, called a perimeter allows detailed analysis of the peripheral field.
Perimetry systematically tests the visual field: It is the measurement of differential light sensitivity in the visual field by the detection of the presence of test targets on a defined background.
Automated perimeters are used to diagnose disease, job selection, visual competence, screenings, military selection, and disability classifications.
The Goldmann perimeter is a hollow white spherical bowl positioned a set distance in front of the patient, and is able to test the entire range of peripheral vision.
The Goldmann perimeter has been used to follow vision changes in glaucoma patients.
Presently, automated perimetry is more commonly used.
Automated perimetry uses a mobile stimulus moved by a perimetry machine, and the patient indicates whether he sees the light by pushing a button.
The sensitivity of white-on-white perimetry is low, and the variability is relatively high..
With white on white perimetry as many as 25-50 percent of the photoreceptor cells may be lost before changes in visual field acuity are detected.
This method is commonly used for detection of blind spots.
A microperimeter assesses the macular function in a computerised way.
Static perimetry tests different locations throughout the field by presenting a dim light at a specific location and it is intensified until it the light is recognized defining the sensitivity of that location.
Using the above technique at multiple locations provides a view of the entire visual field.
Threshold static perimetry, using automated equipment, is used for screening and follow up of diseases involving deficits such as scotomas, loss of peripheral vision and more subtle vision loss.
Perimetry testing is indicated in the screening, diagnosing, and monitoring of eye, retinal, optic nerve and brain disorders.
A single test light of constant size and brightness is used, and moved towards the center of vision from the periphery until it is first detected by the patient.
By repeatedly approaching the center of vision from different directions mapping visual field sensitivity boundaries can be achieved.
Kinetic perimetry uses a mobile stimulus and is useful for mapping visual field sensitivity boundaries.
Perimetry is one way to systematically test the visual field.
It is the systematic measurement of differential light sensitivity in the visual field by the detection of the presence of test targets on a defined background.
Perimetry more carefully maps and quantifies the visual field, especially at the extreme periphery of the visual field.
Microperimetry assesses the macular function in a similar way to perimetry.
Microperimetry enables precise structure-function correlation, and allows for examination of patients with unstable fixation.
Fundus imaging is performed at the same time, and allows for fundus tracking to ensure accurate stimulus placement.
The most commonly performed perimetry test uses white stimuli on a bright white background referred to as photopic white-on-white testing.
This tests isolated L- and M-cone function and is applied in the setting of glaucoma.
Following 30 minutes of dark-adaptation, it is possible to selectively test rod function using short-wavelength stimuli on a dark background.