Visual Fields Flashcards
The entire area that can be seen when the eye is directed forward, including that which is seen with peripheral vision.
Or
The entire expanse of space visible at a given instant without moving the eyes.
Visual Field
Visual Acuity
The ability to resolve something
Visual Field Tests that are used:
- Conformation
- Tangent screen
- Amsler Grid (wavy line?)
- Automated Perimetry
Visual Field Test
A test that measures the extend and distribution of the field of vision
What are the diseases that can adversely affect the visual field?
- glaucoma
- strokes (CVA)
- tumor
What medications can affect the visual field?
Hydroxychloroquine (Plaquenil) toxicity
Why do we do VF testing?
- Many diseases can affect VF
- Medications can affect VF
- Occupational safety standards
- Determination of functional loss
Give examples of occupational safety standards that are determined by VF’s
- Driver’s License qualification
- Pilots (private, commercial, military)
Give reasonings for why we do vision field testing for the determination of functional loss:
- benefits for loss of VA
- insurance reimbursements (cosmetic vs. medically necessary)
Name the different levels of Visual Field Testing
- Visual Field Screening
- Qualitative or Diagnostic Field Testing
- Quantitative Visual Field Testing
Describe VF screening
- generally done when VF loss is unlikely but possible
- should be quick, easy and capable of eliciting a wide variety of defects
Describe Qualitative or Diagnostic Field Testing
Designed to determine the characteristics of a VF defect (location, borders, size, shape, etc)
Examples: special DL testing, ptosis functional loss assessment, etc
Describe Quantitative Visual Field Testing:
-Most sophisticated Fully quantifies a known or suspended defect, so future changes detectable Requires automated (full threshold) perimetry
Incidence of VF loss is about ____
3-5%
over the age 65: 10-15%
One study (n=1500) found ___ of those appearing for first optometric eye exam had VF defects and in half the cause was sight- or life-threatening
4.4% (1 in 20-25 people)
VF defects are often _____ and may be the only detectable evidence of a disease/disorder
asymptomatic
Should VF screening be done at all comprehensive eye exams?
Yes, with more extensive VF screening indicated whenever possible VF loss arises
Describe Confrontation Visual Fields Tests.
- Can be done in multiple ways
- A quick, simple way to screen for gross VF loss
- Does not require special equipment and can easily be done with homebound or bedridden patients
- Sensitivity is not very high (better for posterior visual pathway lesions rather than anterior pathway lesions)
Describe the technique for Confrontation VF’s
(counting fingers)
- Have them take off their glasses if they have them. Contacts are ok
- Examiner sits facing the patient (about 1 meter away)
- Patient covers 1 eye (test is done on each eye separately)
- Have patient look straight ahead into appropriate eye of the examiner
- Examiner introduces fingers (one, two or four) in each quadrant while making sure patient maintains fixation straight ahead (into their eye)
True/False: A patient may come to you with no visual complaints, 20/20 VA, yet may have loss in VF.
True!
True/False: Asymptomatic field loss may be the only detectable evidence of a serious medical condition.
True!
True/False: Confrontation visual field examination, when done properly, can uncover otherwise undetectable pathology and potentially save a life.
True
Common methods for assessing Central Visual Field?
- Amsler Grid testing
- specialized automated VF test strategies
When should you test Central Visual Fields?
When macular disorders are suspected
Unlike peripheral VF’s, ____ is not routinely screened for.
Central VF’s
Describe Amsler Grid testing.
- Simple, quick way to check for defects within the central portion of the VF
- Assesses roughly the central 10 degress of the VF
- qualitative assessment of macular function
What is the macula?
Portion of retina responsible for central vision
This test should be:
- done to detect gross abnormalities that may be caused by suspected disorders of the macula (e.g. AMD, etc)
- may be given to patients with instructions on how to use themselves at home to monitor such conditions themselves
Amsler Grid Testing
This defect within a field of vision is a distortion that can be found using an Amsler Grid testing.
Scotoma
What is the normal response for an Amsler Grid Test?
- Dot at center is seen when looking directly at it
- All four corners seen when looking at the dot
- No areas of the grid are missing
- No areas of the grid are distorted (no wavy lines)
Abnormalities within Amsler Grid Testing may detect a defect at the _____.
What can this indicate?
central VF
This may confirm macular dysfunction in someone suspected of macular disorder
____ may be used to monitor change for those with known Central VF defects.
Amsler Grid
Describe Normal Visual Fields
- Full in extent (up, down, left and right) in both eyes
- Free of “blind spots” (within visual field)
- Free of areas of distortion (within visual field)
