Confrontational Visual Fields

Question 1

Define the visual field. What is the best way to test this? What part of the visual pathway does it test?

Answer 1

The total area in which objects can be seen in the side (peripheral) vision as you fixate on a central point

Easier and better to test health by testing function (VF) rather than appearance (BIO)

Visual field tests the entire visual pathway instead of just testing the superficial layer

Question 2

What is the extent of the VF?

Answer 2

60 superiorly and nasally
70 to 75 inferiorly
90-100 temporally

Binocularly extends 180 side to side
Area of vision common to both eyes extends 60 on either side of nose

Question 3

Why is Visual acuity not a good indicator of the retina?

Answer 3

Can have extensive retinal damage close to fovea or mid-periphery without vision acuity loss

Question 4

Define static perimetry.

Answer 4

The position and size of stimulus (target) is held constant while the stimulus intensity (brightness) is varied

Question 5

Define kinetic perimetry.

Answer 5

The intensity and size of the stimulus are held constant while the stimulus is moved from one location to another

Ex: Goldman visual field analyzer

Test different isopters where the size, color, and intensity of the stimulus varied

Ex: bjerrum/tangent screen

Question 6

Compare central and peripheral field.

Answer 6

Central- portion of the visual field within 30 of fixation

Peripheral- from 30 outwards

Question 7

Define scotoma.

Answer 7

A localized defect or depression in the visual field
The normal blind spot is an absolute scotoma

Question 8

Define absolute defect.

Answer 8

A field defect that persists when the maximum stimulus of the testing apparatus is used

Question 9

Define relative defect.

Answer 9

A field defect that is present to weaker stimulus but disappears when tested with a brighter stimulus

Question 10

Compare the sensitivity of the fovea compared to the peripheral retina.

Answer 10

Fovea- greatest sensitivity to light (lowest threshold), can see weakest or smallest stimulus

Peripheral retina- less sensitivity to light (higher threshold) needs stronger stimulus

Question 11

Describe the blind spot on the optic nerve. What is its location?

Answer 11

Insensitive to light (absolute defect)
Optic nerve is nasal to fovea (temporal on VF chart)
Blind spot is on right ride for OD and left side for OS

15.5 temporal to fixation and 1.5 below the horizontal
7.5 and 5.5 (vertical and horizontal dimensions)

Question 12

What 3 methods can be used to measure confrontation visual fields?

Answer 12

Finger counting
Finger wiggle
Kinetic red

Question 13

Describe extinction phenomenon.

Answer 13

Patients may have normal VF when single target is presented but when multiple target are present, one of the two stimuli is not detected

Question 14

Describe finger wiggle to measure CVF.

Answer 14

Two finger are presented on either side of vertical meridian (20 eccentric to fixation in superior and inferior quadrants)
Patient is asked to report which finger wiggled (they should not be oscillated more than 5)
Does have extinction phenomenon

Question 15

Describe kinetic Red.

Answer 15

No extension phenomenon
5mm diameter red pin is moved inwards
Ask when patient first perceives pin as red
No color vision (cones) in periphery

Question 16

Which CVF is best to perform? Which is the worst?

Answer 16

Kinetic red is best

Kinetic red and finger wiggle if performing 2

Finger counting is worst (worst sensitivity and specificity)

Question 17

Where should the target be placed for all CVF tests?

Answer 17

Target should be halfway between practitioner and patient

Question 18

What is the purpose of the amsler grid? To what extent does the grid test?

Answer 18

To test the integrity of the central visual field (macula)

Test at 30cm where each small square corresponds to 1 degree, so card tests 10 degrees away from fixation in all directions

Question 19

What is the procedure for amsler gird?

Answer 19

Habitual near Rx
Uniform illumination
Monocular

Question 20

What do we ask the patient?

Answer 20

Do you see a dot in the center of the grid?
As you look at central dot are you aware of all four corners?
As you look at dot in center, are you aware of all the lines going up and down and side to side?
Are any lines missing, wavy or distorted?
Are any of the lines blurry?

Question 21

What should we do if patient cannot see center dot on amsler grid?

Answer 21

Switch to dark grid with x going across
Ask patient to fixate where they think the center of the X is

Question 22

Define metamorphopsia.

Answer 22

Portion of the grid may appear smaller or larger than another portion of the grid or the entire grid may appear smaller or larger when compared to the other eye

Question 23

Define micropsia.

Answer 23

Portion or entire grid appears smaller
Due to fluid that may spread apart the photoreceptors

Ex: macular edema

Question 24

Define macropsia.

Answer 24

Portion of the grid or entire grid appears larger
Due to abnormal compression on the photoreceptors

Ex: tumor or mass

Question 25

What are the effects of ARMD on the amsler grid?

Answer 25

Distortions
Macropsia

Question 26

What do we record as results for the amsler grid?

Answer 26

No defect noted
If defect found, record size and quadrant, and abnormality
Note any metamotphopsia

Can have patient mark

Question 27

How can we test a larger portion of the central VF using Amsler grid?

Answer 27

Repeat the amsler grid test, with the patient fixating on the bottom right, left and top right and left corners

This tests 20 degrees away from fixation in all directions