Visual fields Flashcards
visual fields
Widest temporally
Island of vision
The blind spot is 15 degrees from fixation (corresponding to the displacement of
the optic nerve from the fovea)
normal field extents
90-100 degrees temporally
60 degrees nasally
70-80 degrees inferiorly
50-60 degrees superiorly
kinetic perimetry
GVF
Usually done manually
“Slices” the island of vision into isopters which can be plotted
GVF
Controller on machine allows selection of stimulus size and illumination
Patients sit oppority a white hemipshereical bowel with fixation at 33cm
GVF maximum brightness
1000 apostilbs
GVF roman numerals
I - V
size in diameter, 1/2 each time
II = 1mm2
III = most commonly used
V = biggest target
GVF number
1- 4
brightness of the stimulus
drop = 5dB
GVF letter
a-e
finer calbirations of brightness
drop 1 Db
GVF plot
Armaly Drance technique used to plot:
o Concentrates on nasal horizontal
o Tests pericentral area with a suprathreshold stimulus to exclude central
scotomas
Luminosity range
0.08 to 10,000 apositlibs
Inverted scale
0 to 52 ab
Static threshold perimetry
Measures the “thickness” of the island
Lighter grayscale indicates thicker areas of better vision and darker/black areas
indicate poor vision
Humphrey, Octopus etc.
Finds threshold at
the intensity of light seen 50% of the time
Measured in decibels of attenuation of the light
Light presented for less than 0.5 second
White target on white background: achromatic
maximum brightness
10,000 apostilbs
benefits of HVF
standardised
less user depednant
numerical output
HVF 24-2
evaluates 24 degrees with 54 points
HVF 10-2
evaluates 10 degrees with 68 points
HVF 30-2
evaluates 30 degrees with 76 points
how much of the visual cortext relates to the central visual field
80%
thf central 24 correlates to 30 degrees
central 10 degrees is best for
paracentral scotomas
global indicies
Summary of results condensed into one figure, mainly used to monitor
glaucoma progression
total deviation
Deviation of patient’s result from age-matched controls
mean deviation
Average deviation of sensitivity from age adjusted normal population
pattern standard deviation
Average deviation from the normal hill of vision after correcting for overall
sensitivity differences
corrected PSD
PSD after accounting for short-term fluctuation (an indication of consistency
achieved by testing ten points twice and assessing the difference)
fixation loss in HVF
patient responds to a target presented at their blind spot
false-negative in HVF
atient fails to respond to a suprathreshold target at a location
that is expected to be seeing
false positve in HVF
the machine makes a familiar noise and alters the motorised
light but does not present a target and the patient responds as if seeing one
(trigger-happy
perimetric errors
miotic pupil
cloveleaf deaf - malingering
lens rim arterfact
refractive error
Unilateral central scotoma
Optic nerve pathology: compressive lesions, optic neuritis
Macular pathology: scarring, oedema, etc
Bilateral central scotoma
Optic nerve pathology: toxic/nutritional
Macular pathology: scarring, oedema etc.
Causes of cecocentral scotoma
pathology extending from disc to macular or vice versa).As above, same as the causes of central scotoma, but in addition:
o Optic disc pit with serous detachment
o Inherited optic disc pathology: Leber’s, autosomal dominant optic atrophy etc.
arcuate scotoma
damage to nerve fibre bundles that extend to the blind spot)
o Glaucoma
o Anterior ischemic optic neuropathy
o Branch retinal artery/vein occlusion
o Optic nerve drusen
altituidinal defect
this is a defect that respects horizontal midline and is characterised by damage to the optic disc poles
o Hemiretinal artery/vein occlusion
o Optic neuritis
o Anterior ischemic optic neuropathy
binasal defect
o Glaucoma in most cases
o Compression of the temporal optic nerve/chiasm
o Internal carotid artery aneursym
o Infarction
