Test 1 Material

Question 1

How much does a threshold vary by in normal individuals?

Answer 1

3dB in normal individuals

Can vary more in the presence of disease (6-8dB)

Question 2

What is the range of the Normal Hill of Vision?

Answer 2

90+ degrees temporally
~60 degrees nasally/superiorly
~70 degrees inferiorly
Blindspot is temporal because the nerve is nasal!

Question 3

Why is a 200ms stimulus duration used for visual fields?

Answer 3

200ms is enough time to recognize it but not enough time to change fixation to it

Question 4

What is the standard Goldmann stimulus size?

Answer 4

III (3)

Question 5

What are the two types of Suprathreshold testing? Explain them briefly.

Answer 5

1. Single Intensity screening:
   The stimulus intensity is relatively bright and does not change. This results in a pass/fail criterion that is variable by position. Single intensity screening does not yield quantitative information, making it bad at detecting subtle VF defects.
2. Threshold Related Screening:
   The stimulus varies in intensity based on the expected threshold for each point. This creates a pass/fail criterion that is constant by position. Threshold related screening has increased sensitivity compared to the single intensity but there is still no quantitative information.

Question 6

Explain threshold testing.

Answer 6

Threshold testing is the gold standard for visual fields and glaucoma management. It repeats the sampling point with varying stimuli to bracket around a patient’s threshold. Threshold testing also gives both qualitative and quantitative data that can be used to detect subtle defects in a visual field.

Question 7

Briefly explain the advantages/disadvantages of the Humphrey FDT.

Answer 7

Advantages: 
1. Quick to administer
Disadvantages: 
1. Large, fixed stimulus size (hard to detect subtle defects) 
2. No fixation monitoring 
3. Limited screen size (patient view)

Question 8

Briefly explain how the Humphrey Matrix FDT is an improvement over the Humphrey FDT.

Answer 8

Matrix improvements over original FDT:

1. Smaller stimulus
2. Fixation monitoring ability
3. Larger screen size
4. The matrix can run a full threshold test in addition to a screener!

Question 9

What range of vision does the Humphrey FDT measure?

Answer 9

Central 20 degrees

Question 10

What is the gold standard of visual field testing?

Answer 10

Humphrey Visual Field Analyzer

Question 11

What is a visual field defect?

Answer 11

Any statistically significant reduction of sensitivity compared to a normal hill of vision

Question 12

What is a scotoma? Explain how scotomas are described.

Answer 12

1. Scotomas are areas of decreased sensitivity that are surrounded by a normal/near normal area of vision.
2. Scotomas can be partial/relative (called a depression) or complete/absolute (called a contraction).
3. Scotomas can also be positive or negative. Positive scotomas are areas of decreased sensitivity that the patient is aware of. Negative scotomas occur when the patient is NOT aware of the defect.
4. Scotomas are described on many characteristics like position, shape, size, intensity, uniformity, margins, onset/course, and if it’s unilateral or bilateral.

Question 13

What is a positive scotoma? A negative scotoma? Relative scotoma? Absolute scotoma?

Answer 13

Positive Scotoma: A defect in vision that the patient is aware of
Negative scotoma: A defect in vision that the patient of unaware of
Relative scotoma: A partial deficit in a patient’s sensitivity
Absolute scotoma: A complete deficit in a patient’s sensitivity (total loss of sensitivity)