Confrontation Visual Fields

What is a visual field?

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

Is it more important to look at the structure or function of the peripheral retina?

structure is important but function is more imporant

probably easier (and perhaps better) to assess the health of the peripheral retina by testing its function (VF), rather than just looking at it (BIO)

How much of the visual pathway is tested by visual field?

the entire pathway (rather than just viewing the most superficial layer)

What is the extent of the visual field temporally?

90-100 degrees

What is the extent of the visual field nasally?

60 degrees

What is the extent of the visual field superiorly?

60 degrees

What is the extent of the visual field inferiorly?

70 to 75 degrees

What is the extent of the visual fields of both eyes together extend approximately

180 degrees from side to side

What is the extent of the visual field that overlaps between the two eyes?

60 degrees on either side of the nose. This combined field is known as the binocular field of vision.

Can a patient have good VAs but a poor visual field?

yes; can have extensive retinal damage close to the fovea or mid-periphery without VA loss

What is static perimetry?

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

What is kinetic perimetry?

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

What is an example of kinetic perimetry test?

Goldmann visual field analyzer

Test different isopters, where

the size, color, and intensity of the stimulus is varied.

If there is a small isopter what does that mean about the stimulus?

the stimulus is hard to detect

What is the central field?

portion of the visual field within 30 degrees of fixation

What is the peripheral field?

from 30 degrees outwards

What is a scotoma?

a localized defect or depression in visual field. the normal blind spot is an absolute scotoma.

What is an absolute defect?

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

What is an example of an absolute defect?

normal blind spot caused by optic nerve

Waht is a relative defect?

a field defect that is present with weaker stimuli but disapears when tested with abrighter stimuli

Where is the greatest sensitivity to light?

fovea
has a low threshold, and therefor can see the weakest stimulus

Where is there less sensitivity to light?

peripheral retina
higher threshold, needs a stronger (or larger) stimulus than the fovea

What is the hill of vision?

a diagram of when sensitvity of vision based on region of the retina

What causes the blind spot?

anatomical structure of the optic nerve head

Where is the optic nerve located compared to the fovea?

nasal to the fovea

Where is the blind spot located compared to fixation?

15.5 degrees temporally and 1.5 degrees inferior

When looking at a visual field plot where will the blind spot be for a right eye?

to the right

What is the size of the blind spot?

7.5 degrees vertically and 5.5 degrees horizontally

What are confrontation visual field tests?

1) finger counting

2) finger wiggle

3) kinetic red

Where should the target be placed during confrontation visual field tests?

half way between patient and doctor

How are confrontation visual fields measured?

comparing the doctors field to the patients

What is extinction phenomenon?

patients may have a normal visual field when a single target is presented, but when multiple targets are presented, one of the two stimuli is not detected/

How is finger wiggle test performed?

two fingers are presented simultaneously on either side of the vertical meridian approximately 20 degrees eccentric to fixation in the super and then inferior quadrants.

the patient is asked to report which of the fingers wiggled

How is kinetic red performed?

5mm diameter red pin is moved inwards from beyond the boundary of each quadrant along a diagnonal line that bisects the horizontal and vertical meridian.

pt is asked to report when the pin is first perceived to be red

What does kinetic red test?

the extent of cone function

Which confrontation visual field test has the most sensitivity and specificity?

kinetic red

Which confrontation visual field test has the worst sensitivity and specificity?

finger counting

What is the purpose of an amsler grid?

test the integrity of the central visual field

How much of the visual field is tested in all directions?

10 degrees away from fixation in all directions

How much of the visual field is represented by each box of the amsler grid?

1 degree (when test distance is 30cm)

What is the test distance for amsler grid?

30cm (13”)

What is the procedure for amsler grid?

-habitual near correction

-uniform illumination

-monocular

What is the total amount of visual field being tested by amsler grid?

central 20 degrees

What are the instructions to the patient for Amsler grid?

1) do you see the dot in the center of the grid?

--look at that dot

2) when looking at the dot are you aware of all four corners of the grid?

3) when looking at the dot are you aware of all the lines going up and down and side to side?

4) are there any lines missing, wavy, or distorted?

5) are any of the lines blurry?

What do you do if the patient cannot see the center dot of the amsler grid?

give patient a grid with two diagonal lines crossing and ask the patient to stare at where these lines would come together

What is metamorphopsia?

portion of the grid may appear smaller of larger than another portion of the grid

or the entire grid may appear larger or smaller when compared to the other eye

What is micropsia?

portion or entire grid looks smaller

What causes micropsia?

fluid that may spread apart the photo receptors, i.e, macular edema

What is macropsia?

portion or entire grid looks larger

What caused macropsia?

abnormal compression on the photoreceptors, i.e. tumor or mass

How do you record for amsler grid with no defects found?

OD/OS: no defects

How do you record for amsler grid with defects found?

record size and the quadrant of the defect and the abnormality

-have patient mark on the grid where they see the defect and write a note in the margin to describe the defect in more detail

How can you test a larger portion of the patients visual field with the amsler grid?

repeat the Amsler grid test but this time have the patient fixate on one corner of the chart at a time

-this will test 20 degrees of the visual field in every direction