Visual Fields

Question 1

What are Visual Fields

Answer 1

Visual field: 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

Question 2

What is Visual Field Testing?

Answer 2

Visual field test: A test that measures the extent and distribution of the field of vision.

Question 3

A visual field test may be done via a number of methods, including:

Answer 3

• confrontation visual field testing
• Amsler grid
• tangent screen
• automated perimetry

Question 4

Why do VF testing?

Answer 4

1. Many diseases can adversely affect the visual field, including: • glaucoma • strokes (CVA) • Tumors
2. Medications can also affect the visual field • E.g., hydroxychloroquine (Plaquenil) toxicity
3. Occupational safety standards are determined by VF’s • Driver’s license qualification • Pilots (private, commercial, military)
4. Determination of functional loss • Benefits for loss of vision • Insurance reimbursement (cosmetic vs. medically necessary)

Question 5

Visual field screening

Answer 5

• Generally done when VF loss unlikely, but possible

* Should be quick, easy, and capable of eliciting a wide variety of defect

Question 6

Qualitative or diagnostic field testing

Answer 6

Designed to determine the characteristics of a VF defect (location, borders, shape, size, etc.)
• For example: special DL testing, ptosis functional loss assessment, etc.

Question 7

Quantitative visual field testing

Answer 7

• Fully quantifies a known or suspected defect, so future changes detectable
• Requires automated (full threshold) perimetry

Question 8

The why and when of VF screening?

Answer 8

• Incidence of visual field loss about 3-5% (10-15% in those over age 65).
• One study (n=1500) found 4.4% of those appearing for first optometric eye exam had VF defects and in half the cause was sight- or life-threatening.
• VF defects are often asymptomatic and may be the only detectable evidence of a disease/disorder.

Question 9

Confrontation Visual Fields

Answer 9

• 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 not very high (better for posterior visual pathway lesions than anterior pathway lesions)

Question 10

Technique for Confrontation VF’s (counting fingers)

How far away does the examiner sit in front of the patient?

Answer 10

Examiner sits facing patient (about a meter in front of them)

Question 11

Technique for Confrontation VF’s (counting fingers)

Is this test done with one eye or both?

Answer 11

Patient covers one eye (test is done on each eye separately). Have patient look straight ahead into appropriate eye of examiner.

Question 12

Technique for Confrontation VF’s (counting fingers)

Should they wear their glasses or contact lenses?

Answer 12

No for glasses

Can wear contacts

Question 13

Technique for Confrontation VF’s (counting fingers)

How many fingers should the examiner use?

Answer 13

Examiner introduces fingers (one, two, or four) in each quadrant while making sure patient maintains fixation straight ahead (into their eye)

Question 14

What are tips to obtaining reliable confrontation VF’s?

Answer 14

• Make sure target presented to your patient at corresponding point in your own VF (assumes you have normal fields).
• Don’t make it too hard or too easy!
• Make sure entire target remains completely within the quadrant you intend to assess.
• Recognize deceptive responses (feigned sight or malingering) and know how to detect it.

Question 15

How & when to assess the central VF?

Answer 15

• Central field loss is usually, but not always, associated with reduced visual acuity.
• Therefore, unlike peripheral VF’s, central VF loss is not routinely screened for.
When macular disorders are suspected, function should be assessed via some form of central VF testing:

Question 16

Common methods for assessing central VF’s include:

Answer 16

• Amsler grid testing

* Specialized automated VF test strategies

Question 17

What is Amsler grid testing?

Answer 17

A simple, quick way to check for defects within the central portion of the visual field.

Question 18

How many degrees does the Amsler grid test measure?

Answer 18

Assesses roughly the central 10 degrees of the VF

Question 19

What area of the eye does the Amsler grid assess? Is this a qualitative or quantitative assessment?

Answer 19

A qualitative, rather than quantitative, assessment of macular function (macula = portion of retina responsible for central vision).

Question 20

What are indications for using the Amsler grid?

Answer 20

• 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 .

Question 21

What is a normal response to the Amsler grid?

Answer 21

Normal response is:
• Dot at center seen when looking directly at it.
• All for corners seen when looking at dot.
• No areas of the grid missing
• No areas of the grid distorted (no “wavy lines”)

Question 22

What is an abnormal response to the Amsler grid?

Answer 22

Anything abnormal indicates a defect of the central VF. • This may confirm macular dysfunction in someone suspected of having a macular disorder • Also used to monitor for change in those with known defects

Question 23

Normal visual fields should be:

Answer 23

Normal VF’s:
• Full in extent (up, down, left, and right) both eyes.
• Free of “blind spots” (within visual field).
• Free of areas of distortion (within visual field).