Visual Fields Flashcards
Visual field definition
The entire area that can be seen when the eye is directed forward, including peripheral vision.
Visual field vs Visual Acuity
Hmmm
What is a Visual Field Test?
A test that measures the extent and distribution of the field of vision.
Methods of Visual Field Testing
Confrontation visual field testing
Amsler grid
Tangent screen
Automated perimeter
Why do VF testing?
Diseases can adversely affect VF
Medications can affect VF
Occupational safety standards are determined by VF (drivers license, pilot)
Determination of functional loss (loss of vision, whether or not insurance will cover)
Diseases that can adversely affect VF
Glaucoma, strokes (CVA), tumors
Levels of VF Testing
VF Screening,
Qualitative or diagnostic field testing,
Quantitative visual field testing
Visual field screening
Generally done when VF loss unlikely, but possible
Should be quick, easy, and capable of eliciting a wide variety of defects
Qualitative/diagnostic field testing
Designed to determine the characteristics of a V defect (location, borders, shape, size, etc)
Ex:
DL testing, ptosis functional loss assessment
Quantitative visual field testing
Fully quantifies a known or suspected defect, so future changes detectable
Requires automated (full threshold) perimetry
Incidence of VF loss (percentage)
About 3-5 %, 10-15% in 65+
Are VF screenings required at comprehensive eye exams?
Nope, but recommended.
What isn’t included in the binocular visual field?
Left and right monocular temporal crescents
What is Confrontation VF?
Can be done in numerous ways
Quick and simple screening for VF loss
Doesn’t require special equipment
Sensitivity isn’t very high
Counting Fingers technique
Version of Confrontation VF
Examiner faces pt,
Pt covers one eye,
Pt looks straight ahead,
Examiner flashes fingers in each quadrants while making sure pt remains fixated
Should not wear glasses due to frames’ blind spots
Tips for obtaining reliable confrontation VFs:
Make sure target presented to your patient at corresponding at corresponding point in your own VF
Don’t make too hard or too easy
Make sure entire target remains completely within the quadrant
Recognize deceptive responses (feigned sight or malingering) and know how to detect it!
Can patients still have 20/20 VA and VF loss?
Yessss
A symptomatic field loss may be the only detectable evidence of a ____________________
Serious medical condition
Seriously
When should VF screening testing be done?
At every comprehensive exam, and whenever possibility of VF loss arises
Confrontation visual field examination can ruin lives, true or false.
False. Duh. It can save lives. And it can uncover otherwise undetectable pathology.
Central field loss is usually, but not always, associated with:
visual acuity
That’s why central field loss isn’t routinely screened for
Techniques for assessing central VFs
Amsler grid testing
Specialized automated VF test strategies
Amsler Grid Testing
Simple, quick check for defects in central portion of visual field
Assesses central 10 degrees of VF
Qualitative assessment of macular function
What is the macula?
Portion of the retina responsible for central vision
When should Amsler Grid testing be done?
When suspected disorders of macula arise,
Can be given to patients to monitor at home
Normal response of Amsler Grid
Dot at center,
All four corners,
No missing areas of grid,
No areas of grid distorted (no wavy lines)
