Visual field testing

Question 1

What is Traquair’s analogy about the visual field?

Answer 1

the VF is an island of vision surrounded by a sea of darkness

Question 2

What is a real-life analogy of the visual field?

Answer 2

three-dimensional hill, the peak of the hill being the fovea

Question 3

To what degrees does the visual field extend in all directions?

Answer 3

superiorly: 50 degrees
nasally: 60 degrees
inferiorly: 70 degrees
temporally: 90 degrees

Question 4

What are the indications for visual field testing?

Answer 4

aids diagnosis and monitors certain ophthalmic (e.g. glaucoma) and neurological disease

Question 4

What are the indications for visual field testing?

Answer 4

aids diagnosis and monitors certain ophthalmic (e.g. glaucoma) and neurological disease

Question 5

What is an absolute vs relative scotoma?

Answer 5

• absolute = total loss of vision where no light can be perceived
• relative = area of partial visual loss where bright lights or larger targets are seen, whereas smaller and dimmer ones cannot be seen

Question 6

What is an absolute vs relative scotoma?

Answer 6

• absolute = total loss of vision where no light can be perceived
• relative = area of partial visual loss where bright lights or larger targets are seen, whereas smaller and dimmer ones cannot be seen

Question 7

What is meant by congruousness with regards to visual fields?

Answer 7

describes the degree to which the field defects match between the two eyes. more congruous = more posterior along visual pathway the lesion is located

Question 8

What is meant by isopter?

Answer 8

a threshold line joining points of equal sensitivity on a VF chart

Question 9

What is a key factor that can cause interpretation problems of all VFs?

Answer 9

refractive status

Question 10

By how much can refractive status influence interpretation problems with VFs?

Answer 10

overcorrection by 1D will cause a reduction in sensitivity of 3.6dB

Question 11

What are 4 things which must be standardised in order to properly compare serial VFs?

Answer 11

1. background luminance
2. stimulus size
3. intensity
4. exposure times

Question 12

What are 4 times of VF assessments?

Answer 12

1. confrontational VFs
2. Amsler grid
3. Kinetic perimetry
4. Static perimetry

Question 13

What are 2 examples of kinetic perimetry?

Answer 13

1. Tangent screen (Bjerrum screen)
2. Goldmann perimetry

Question 14

What is a key type of static perimetry?

Answer 14

Humphrey perimetry

Question 15

What is a key type of static perimetry?

Answer 15

Humphrey perimetry

Question 16

What can be used for confrontation VFs to detect subtle defects?

Answer 16

hat pins (white and red)

Question 17

Which part of the visual field is assessed by the Amsler grid?

Answer 17

central 10 degrees of the visual field

Question 18

What are 2 advantages of the Amsler grid?

Answer 18

1. easy to perform
2. portable

Question 19

What is the Amsler grid used to test for?

Answer 19

used to detect central and paracentral scotomas

Question 20

At what distance is the Amsler grid held?

Answer 20

33cm

Question 21

How much does each square on the Amsler grid subtend?

Answer 21

1 degree of VF

Question 22

What is the overarching principal of kinetic perimetry?

Answer 22

• presents a moving stimulus of known luminance from a non-seeing area to a seeing area
• the target is then presented at various points around the clock and marked when recognised
• points are then joined, producing a line of equal threshold sensitivity which is named the isopter

Question 23

What is another name for the Tangent screen and how frequently is itused in clinical practice?

Answer 23

Bjerrum screen - not commonly used

Question 24

What part of the VF is examined by the Tangent screen?

Answer 24

central 30 degrees of VF

Question 25

At what distance is the Tangent screen performed?

Answer 25

usually 2m (although 1m chart also available)

Question 26

What is the method for performing Tangent screen kinetic perimetry?

Answer 26

• patient sits at 2m (2000mm) away from the screen and wears corrective lens for distance, if required
• the non-tested eye is occluded in turn
• patient fixates at a central spot and informs the operator when they see the targets
• white (w) or red (r) disc targets are used, either 1 or 2mm in diameter

Question 27

How are the results of the Tangent screen kinetic perimetry processed?

Answer 27

• results plotted on charts at the patient sees them
• target size and colour are the numerator (1w, 2w, 1r or 2r) and the denominator is the distance (mm) of the patient from the chart (e.g. 1r/2000)

Question 28

What is the commonest type of kinetic perimetry in clinical practice?

Answer 28

Goldmann perimetry

Question 29

What is the commonest type of kinetic perimetry in clinical practice?

Answer 29

Goldmann perimetry

Question 30

What is the name of the automated Goldmann machine in use?

Answer 30

Haag-Streit

Question 31

What is most automated perimetry based on?

Answer 31

static on-off stimuli of variable luminance presented throughout the potential field