Visual Fields - Clinical

Question 1

what is the clinical visual field?

Answer 1

all the space an eye can see at a given time

Question 2

what field does light hit coming from
-the nasal field
-the inferior field

Answer 2

-temporal field
-superior field

Question 3

what causes the blindspot on every visual field?

Answer 3

the optic nerve but as a result of binocular vision we are not aware of it

Question 4

what does the hill of vision demonstrate?

Answer 4

how the sensitivity of the eye to light varies

Question 5

how can you see a visual defect using hill of vision and give an example of what can cause this

Answer 5

a visual defect is shown by any change from the normal topography of the hill of vision. cataract can cause this

Question 6

what are the two types of perimetry visual fields?

Answer 6

kinetic and static

Question 7

what is the most common form of kinetic perimetry compared to what?

Answer 7

goldmann which is where the target is moved manually compared to octopus where the target is automated

Question 8

what are the advatanges of kinetic perimetry?

Answer 8

-not confined to testing algorithms
-can be used on people who cant use a visual field machine

Question 9

what are the limitations of kinetic perimetry?

Answer 9

-needs an experienced practitioner
-Spatial summation of receptive fields results in us being able to see a moving target in the periphery better than a static one
* This means we could miss a damaged area if areas around it are healthy
* Results are dependent on the patient’s reaction time
* We could record the field as being worse than it is

Question 10

what are the two features of automated static perimetry?

Answer 10

-light stimuli are fixed in position within the visual field
-the size of the light stays the same but brightness is varied

Question 11

what are the two types of automated static perimetry?

Answer 11

-suprathreshold
-full threshold

Question 12

what are the advantages of automated static perimetry?

Answer 12

-standardised
-highly repeatable
-not reliant on practitioner experience
-quicker than kinetic perimetry

Question 13

what are the disadvantages of automated static perimetry?

Answer 13

-tests pre determined points
-doesn’t test full temporal field

Question 14

what does threshold do? how is it determined using the 4-2db algorithm?

Answer 14

-determines sensitivity individually for each tested location and offers a detailed view of a patients vision but can be time - consuming.
-determined by the maximum light energy required to elicit a visual response with a 50% detection probability

Question 15

what is SITA

Answer 15

A full threshold static visual field test designed to be quicker than 4-2db so 2 mins compared to 15 mins

Question 16

what are the advantages of threshold perimetry?

Answer 16

-maps hill vision with greater precision
-measured thresholds are compared to an age-matched normal

Question 17

what are the limitations of threshold perimetry?

Answer 17

-can take a long time compared to suprathreshold

Question 18

what are fixation losses on visual fields?

Answer 18

where the machine calculates where the blindspot by shining a light in this area and if the patient responds they are not focussing correctly

Question 19

what causes false positive errors?

Answer 19

the patient has pressed the button when no light has been presented

Question 20

what causes false negatives?

Answer 20

when a very bright light is shone in an area the patient has already responded to which suggests patient is not responding to all the stimuli they can see

Question 21

what can high false negatives suggest?

Answer 21

the patient does have a visual defect

Question 22

what does gross visual field testing do?

Answer 22

describes using a handheld target to detect visual field defects so the larger the target the less sensitive the area

Question 23

how does the amsler grid work?

Answer 23

assess the the health of the macula region, pathology presence means patient may report missing squares or lines may look distorted

Question 24

what is the esterman field test?

Answer 24

a binocular visual field test that is used by DVLA to judge whether a patient’s visual field is full enough to drive

Question 25

look at the powerpoint to see artefacts

Answer 25

ok

Question 26

ipsilateral meaning

Answer 26

used to describe features on the same side of the body

Question 27

contralateral meaning

Answer 27

describes features on the opposite side of the body

Question 28

isopter meaning

Answer 28

a threshold line joining points of equal sensitivity on a visual field chart

Question 29

what is absolute scotoma

Answer 29

no sensitivity to light so the optic nerve is a physiological absolute scotoma

Question 30

what is reduced scotoma?

Answer 30

reduced sensitivity to light compared to the areas around it