Card Set Information
What is a measure of the perimeter of the area of visual field within which a test spot of constant luminance and size is visible?
What is a measure of the increment threshold luminance for a spot of constant size at different visual field locations?
What type of perimetry is most often performed with automated perimeters?
Which type of perimetry involves a moving stimulus?
What are the normal limites of the monocular visual field?
60*, 100*, 75*, 60*
Superior, temporal, inferior, nasal
Is the blind spot on the same or oposite side of the visual field as the eye being tested?
Ex: OD blind spot on right or left of visual field?
Or... is the blind spot nasally or temporally located?
Same side (OD blind spot on right); temporally
What part of the visual field is seen by both eyes at once?
The area of VF that are only seen by one eye is called...?
Monocular Temporal Crescents
What are the normal total and binocular visual field limits?
Total: 200* horizontal; 135* vertical
Binocular: 120* horizontal; 135* vertical
Who described the visual vield as an island hill of vision surrounded by a sea of blindness?
Why did he use this discription?
The sensitivity of the VF is different depending on where you are in that field; fovea is extremely sensitive, so that is the peak
How are isopter size and intensity and size of stimulus related?
The isopter increases in size as you increase the intensity and/or the size of a stimulus
What kind of stimulus might be used to get a large isopter?
large and/or bright
What type of perimetry can be used to test for scotomas?
Static or kinetic, depending on expected results
What is the term used for the actual perimeter of the patient's visual field?
The perimeter of VF is measured using: 4
a single stimulus
of a specific size
and a constant, specific luminance
under specified viewing conditions
For a person with a normal VF, what will be the effect on the isopter if we make the stimulus larger but keep the luminance the same?
The isopter will be larger
For a person with a normal VF, what will be the effect on the isopter if we increase the stimulus luminance, but keep the stimulus size the same?
The isopter will be larter
What type of perimetry is used to determine isopters for patients in the Goldmann Bowl Perimeter and who designed it?
What are the characteristics of size and intensity used in the Goldmann Kinetic Perimeter? Which is the highest? How much of a change in intensity for each step?
: 0-V with V being the largest
: 1-4, with 4 being the highest; 0.5 log unit change
: a-e, with e being the highest; 0.1 log unit change
What is the maximum intensity difference for the Goldmann Kinetic Perimeter? Units?
How many combinations of stimulus size and intensity are available for the Goldmann Kinetic Perimeter? How many are actually used/needed?
only a few
What size stimulus gives more accurate results?
Smaller because it will detect edges better
What is the modern version of the Goldmann perimeter called?
What type of perimetry is most commonly used now and why?
It takes less time
What are the two ways isopters can be plotted on a VF graph?
flat circles; like looking down at the isopters
2-D "hill of vision"; shows sensitivity well
What type of perimetry is a Humphrey VF?
What photoreceptors are being tested when using an HVF? Why?
The patient is not dark adapted, so any defect shown will be to the cones, not rods.
What is changed in an HVF?
size is kept constant
How does the HVF test fixation?
It shows a stimulus where the patient's physiological blind spot is located
Normal vision requires that targets presented to the periphery have (more/less) luminance that the central target.
What do the dark spots on an HVF indicate?
The patient needed more luminance in these areas than a normal patient of teh same age would need to see the stimulus
Under photopic conditions, the tests (VF) are ______. They are detecting a change in luminance from the _______ luminance.
increment threshold tests
Under scotopic conditions, the tests (VF) are _____ because the patient is ______ _______ and the background luminance is ______.
simple detection tests
Most current automated perimeters normally use a background luminance of what? Units? In what range is this?
or 31.4 apostilbs (candela/pi*m
Describe the graph of the influence of dark/light adaptation on VF results. Why does it look this way?
The top line (0 asb), looks like the scotopic island and the bottom line (1000 asb) looks like the photopic island, with some transition lines in between
The top line dips down because the fovea does not function under scotopic conditions
The bottom line has a peak because the fovea is most sensitive in potopic conditions
When testing with peripheral targets, the target should be either ____ or ____.
bigger or brighter
What increases with increasing retinal eccentricity and increased dark adaptation?
What increases with increased light adaptation and proximity to the fovea?
Describe the data on the graph of weber's constant vs. size looks like. Axis?
large stimulus + photopic conditions = flat line; because several ganglion receptive fields are stimulated at once
Smaller stimulus + photopic conditions = peak; because fewer ganglion receptive fields are stimulated at once, so it is more sensitive
X= retinal location
Y= log of stimulus luminance/ background luminance
The best static perimetry stimulus duration is (longer/shorter) than the saccadic eye movement latency and (longer/shorter) than the critical duration for complete temporal summation
The tendencyfor the patient to want to look directly at a stimulus that is flashed in the periphery is called what? How long does this take?
Saccadic eye movement latency
What is the stumulus duration used by most commercial automated perimeters?
What do the numbers mean on the printout for an automated static perimetry? Units?
They are measurements of sensitivity called decibels
An _______ is an absolute unit of luminance traditionally used in perimetry to simplify calculations involving circular stimuli
The ________ scale is a relative, inverted logarithmic scal incorporated in perimetry to measure the sensitivity of the hill of vision
Does a sensitivity of zero decibels on a VF mean the patient is blind at that location?
No! Since there is a limit to the amount of brightness the machine will use, the patient was just unable to see the brightest stimulus used.
What kind of scotoma has an increased threshold but is still measurable?
What kind of scotoma coresponds to NLP vision?
Everyone has an absolute scotoma. (T/F)
What kind of scotoma is the patient aware of the loss in sensitivity?
What kind of scotoma is the patient unaware of the loss in sensitivity?
Give an example of a Negative scotoma.
physiological blind spot
What is the phenomenon that allows a negative scotoma or blind spot to go unnoticed?
Perceptual filling in
What is perceptual visual neglect?
failure to attend to, or represent, sensory information from one side of the body or VF
What is motor visual neglect?
failure to execute movements fully in or towards (usually in the contralateral) one half of the VF
Visual neglect is usualy related to contralateral lesions of the ________ extra-striate visual pathways.
List 3 tests for visual neglect.
line bisection task
visual extinction field
This sensory deficit (visual neglect) only emerges when stimuli are presented simultaneously to the left and right sides
On double simultaneous stimulation, the stimulus presented to the area of the visual field ________ to the side of the brain with the lesion goes undetected.
How is a patient's "useful" VF measured?
by requiring the patient to identify an object at fixation and a different object simultaneously presented at different positions within the peripheral VF