Visual fields Flashcards
visual fields
the entire area that can be seen when the eye is directed forward, including that which is seen with peripheral vision. The visual field can be tested to measure the extent and distribution of the field of vision
the entire expanse of space visible at a given instant without moving the eyes
visual field or field of vision
How is visual field different than VA?
- more concerned with peripheral vision
- VA is how well you can resolve something when looking directly at it
visual field test
measures the extent and distribution of the field of vision
several methods:
- confrontational field testing
- amsler grid
- tangent screen
- automated perimetry
What are some diseases that can affect VF?
- glaucoma
- strokes (CVA)
- tumors
diseases affect on VF vs VA
It will affect VF long before central vision
Pts can have 20/20 VA and VF loss
what medications can affect VF?
plaquenil (hydroxychloroquine)
VF and occupation
driver’s license
pilots
Vf and determination of functional loss
- benefits for loss of vision
- insurance reimbursement
visual field screening
- finds gross defects, not minute defects, not specific
- done when VF loos unlikely but possible
- quick, easy, capable of eliciting a wide variety of defects
qualitative or diagnostic field testing
- shade, quality, location, borders
- designed to determine the characteristics of a VF defect
- special DL testing, ptosis functional loss assessment, etc
quantitative visual field testing
- sophisticated, measure numerically, specific
- fully quantifies a known or suspected defect, so future changes detectable
- requries automated (full threshold) perimetry (humphrey)
incidence of VF loss
3-5%
how many of those appearing for first eye exam had VF defects?
4.4%
how many of first time VF defects were sight or life threatening?
half
VF symptoms
- asymptomatic
- may be the only detectable evidence of a disease/disorder
when should VF screening be done?
-recommended at all CEE
confrontational VF
- quick, simple to screen for gross VF loss
- does not require special equipment, easy for homebound or bedridden pts
- sensitivity not high
- better for posterior visual pathway lesions than anterior visual pathway lesions
technique for confrontation VF
- 1 meter from pt
- pt covers one eye
- look into appropriate eye of examiner
- no glasses
- dr introduces fingers in each quadrant while making sure pt maintains fixation straight ahead
- compare to own (dr) VF
- know how to pick out problem
what if VF abnormal?
- record in chart
- assess
target for confrontation VF
make sure it remains completely with the quadrant, not between
recognize deceptive responses
asymptomatic field loss
may be the only detectable evidence of a serious medical condition
central VF loss
- usually, but not always associated with reduced VA
- not routinely screened for
macular disorders
- when they are suspected, central VF should be done
- VA reduced, color defects indicative of mac problem
common methods for central VF test
- amslers grid
- specialized automated VF test strategies
amsler grid
- simple, quick
- central VF
- qualitative
- detects gross abnormalities that may be mac problems
scotoma
total black out on amsler grid
metamorphopsia
darker, wavy lines on amsler
amsler grid normal response
- dot at center
- all 4 corners seen when looking at dot
- no areas of grid missing
- no distortion
abnormal amsler
- indicated a defect of central VF
- macular dysfunction
- used to monitor for change in those with known defects
any deviation from normal in VF screen
- recognized
- recorded
- addressed
normal VF’s
- full in extent
- free of blind spots
- free of areas of distortion
