PC - Visual Fields - Week 3

Question 1

How can the visual field be represented?

Answer 1

Island of vision in a sea of blindness.

Question 2

What are Amsler grids used for? What is it used to regulate?

Answer 2

Central scotoma/distortions. Used to regulate AMD.

Question 3

Describe what Amsler grids are, and how they work.

Answer 3

Consists of a grid, each square is 5mm, with a focus point in the middle. If the lines appear blurry or are missing, or are black, suggests a disorder.

Question 4

How do metamorphosia, scotoma, and AMD appear on an Amsler grid?

Answer 4

Metamorphosia - a distortion in the lines
Scotoma - blind spot, lines disappear
AMD - distorted lines with a black spot.

Question 5

Under what conditions should Amsler grid testing be conducted?

Answer 5

Fully corrected, and bright conditions. No squinting, and the head/chart must both be straight.

Question 6

What is the best way to know what the patient is seeing when they look at an Amsler chart?

Answer 6

Ask them to draw what they see.

Question 7

If a patient has AMD in one eye, what is the chance of them having it in the other?

Answer 7

40%

Question 8

Can a confrontation test detect glaucoma?

Answer 8

No.

Question 9

Is confrontation done under habitual vision?

Answer 9

Yes.

Question 10

Describe a facial Amsler test.

Answer 10

Ask the patient to look at your face from 75cm away, if your features are blurry etc.

Question 11

Explain what distances are used during a confrontation test.

Answer 11

Heads are held 75cm apart.
Hands are held 50cm away from the patient.
Both heads must be eye level and straight.

Question 12

Describe the confrontation test.

Answer 12

Ask patient to cover their eye entirely with their palms. Ask them to fixate on your corresponding open eye.
Hold up a given number of fingers in the quadrant being tested, and ask them to add them without looking at your fingers. They should be fixating on your open eye.
Test both hemifields twice for confirmation, then repeat for the other eye.

Question 13

Define Neglect and Extinction.

Answer 13

Neglect - when you present fingers in two quadrants, they neglect one quadrant
Extinction - you present fingers in two quadrants, but they get the total wrong, but individual quadrants correct

Question 14

Describe the red cap test.

Answer 14

Hold the cap at 40cm with monocular viewing.
Have the patient tell you the colour of the cap.
Move the cap to the various quadrants, and judge the caps dimness/brightness on a 1-10 scale, assuming when centre-held it is 10.

Question 15

Describe kinetic red cap testing.

Answer 15

Have the patient tell you when the cap changes colour or they can no longer see it.

Question 16

What tests are essential for glaucoma?

Answer 16

kinetic and static perimetry

Question 17

Describe standard automated perimetry.

Answer 17

Is computerised, measuring sensitivity to small white lights presented on a dimly lit background. Performance is compared to a normal curve.

Question 18

Describe the Humphrey notation for perimetry.

Answer 18

Specified as X-Y
X - extent of coverage
Y - 1 if on the midline, 2 if offset from the midline

Question 19

Describe the Medmont notation for perimetry.

Answer 19

Specified as Annn
A can be
-M for macula - 10 degrees
-C for central - 30 degrees
-G for glaucoma - 30 + 50 degrees nasal
-P for peripheral - 50 degrees
nnn is the number of test points.

Question 20

Between Humphrey and Medmont perimetry, which is a grid and which is radial? Does the pattern have any effect?

Answer 20

Humphrey - grid
Medmont - radial
Pattern has no effect.

Question 21

Compare static perimetry screening with static perimetry threshold - advantages.

Answer 21

Screening
Good for the elderly
Cortical defects
Learning/training
Threshold
Confirming a defect
Monitoring for stability

Question 22

Compare static perimetry screening with static perimetry threshold - disadvantages.

Answer 22

Screening
Early subtle defects
Defects
Monitoring disease progression
Threshold
Patients with limited attention spans
Disabled

Question 23

Name the five visual field defects, and damage to the appropriate structure to induce it.

Answer 23

• Total blindness of ipsilateral eye - optic nerve
• Bitemporal homonymous hemianopia - optic chiasm
• Contralateral homonymous hemianopia - optic tract
• Contralateral homonymous superior quadrantonopia - temporal lobe
• Contralateral homonymous inferior quadrantonopia - parietal lobe

Question 24

Describe what the output values are for perimetry, and where they are.

Answer 24

Top left - threshold values
Top right map - greyscale map
Top left map - numerical total deviation map
Middle 2 maps - numerical pattern deviation maps
Under greyscale map - glaucoma hemifield test
Under GHT - VF indices, significant if there is a P value
Bottom 2 maps - total deviation probability maps - most accurate