Visual Field Testing

What are the stimulus options for Goldmann VF testing?

Size: 0 to V

Brightness: 1-4, a-e

Goldmann stimuli 1-4 increase by increments of…

0.5 log units (3.2x brighter as increase)

Goldmann stimuli a-e increase by increments of…

0.1 log units (1.25x brighter as increase)

How is dB related to log?

1 dB = 1/10 of a log unit

dB to log conversions to know

1 dB = 0.1 LU = 0.8x

3 dB = 0.3 LU = 0.5x

10 dB = 1 LU = 0.1x

How does blur affect a VF?

Every D of refractive blur = 1 dB sensitivity loss (at standard size III stimulus)

How do you run a VF for a patient who wears glasses? (Humphrey)

Trial lens with their Rx - presbyopes must add +3.25 to the RE since test distance is 33 cm

If cyl is over 1.00 D must also add cyl lens (instead of SE)

What is kinetic perimetry useful for?

Quick testing of peripheral VF

Driving tests

Disability determination

Post-stroke testing

Substantial VF loss (ex. RP)

Kids or patients who aren’t good at static perimetry

What are the different SCREENING strategies for static perimetry?

Single intensity

Threshold strategy

3 zone strategy

Quantify defects strategy

How does threshold strategy work?

Records either “hit” or “miss” but doesn’t truly quantify the depth of the defect

Starts 6 dB brighter than expected sensitivity

How does 3 zone strategy work?

Sorts responses into “no defect,” “relative defect,” or “absolute defect”

How does quantify defects strategy work?

Missed stimuli are thresholded

When might a threshold strategy be used on VF?

Missed 2+ adjacent points

Any misses w/in 20 degrees of fixation

When peak sensitivity (also called central reference level) is 26 dB or less

What is threshold PATTERN?

The “map” of the points to be shown (ex. 24-2 vs 10-2)

Which VF testing patterns are most common?

24-2 and 30-2

24-2 is smaller and less points

How does 24-2C differ from regular 24-2?

More macular points

What is 10-2 used for?

Suspected small central scotoma or if specific macular testing is desired

What is G Pattern?

W/in the central 30 degrees - the Octopus version of HFA’s 24-2C

What is M pattern?

The Octopus version of the HFA 10-2, but puts more emphasis near the fovea

What are the threshold patterns options for HFA?

24-2, 30-2, 24-2C, 10-2

What are the threshold pattern options for Octopus?

G Pattern, M pattern

What is the Octopus equivalent of the Humphrey Full Threshold?

Octopus Normal Strategy

Humphrey Full Threshold/Octopus Normal Strategy threshold strategy is…

4 dB staircase followed by 2 dB staircase

What is the Octopus equivalent of the SITA?

Octopus Dynamic

SITA/Octopus Dynamic threshold strategy is…

Reduces the number of points shown without a reduction in data quality

4 dB then 2 dB staircase just like Humphrey Full/Octopus Normal

How do SITA and Octopus Dynamic reduce the time/no. of points shown without sacrificing quality?

Starts closer to threshold and uses “maximum likelihood” procedure combined with the staircase

Adjusts pace based on reaction time and automatically stops when uncertainty hits a certain level

Recalculates all threshold values after the test ends

What is the Octopus equivalent of the SITA fast?

Octopus TOP

What strategies are used to make SITA Fast/Faster faster than other test strategies?

Uses 4 dB staircase for most points instead of 4 dB and 2 dB

Does sacrifice some reliability from test to test for the sake of decreasing testing time by 1/3

What are the average times for SITA, SITA Fast, and SITA Faster?

SITA: 4-8 mins

SITA Fast: 2-6 mins

SITA Faster: 1-4 mins

What VF strategy and pattern do we use at OSU? What is its outside-of-OSU equivalent?

24-2 TOP with HFA output

Equivalent to 24-2 SITA Fast

What percentages of false positives, false negatives, and fixation loss would indicate a VF may not be reliable?

False (+) = more than 33% (“trigger happy”)

False (-) = more than 33%

Fixation Loss = more than 20%

How do reliability indices affect VF results?

Just because a reliability indice is a little off doesn’t necessarily mean you should discount/throw out the entire field—could still have valuable information

Fixation loss and gaze tracking are only available on which type of VF?

HFA

…because Octopus pauses the test if it detects the patient not fixating

What does the HFA Total Deviation Plot show?

Decibel difference between the patient’s test results and the age-match norms using numbers and symbols

• Negative numbers = worse than normal

• Symbols represent the probability of a data point being normal (darker symbol = less likely normal)

What does the HFA Pattern Deviation Plot show?

Similar to total deviation, but adjusted for a change in the overall sensitivity (cataract)

What are global indices of field loss?

These are 1-number summaries of function and loss on a VF

ex. Mean deviation, pattern standard deviation, visual field index

What is mean deviation?

Numerical value representation of the total deviation plot, with more weight given to central points

What mean deviation values would be given for normal field, legal blindness, and extreme field loss?

Normal field: 0 or near 0

Legal blindness: -22 dB

Extreme field loss: -30 dB to -35 dB

What is the pattern standard deviation?

Reflects the extent of the localized defects and how much the SHAPE of the field departs from normal

Close to 0 for both normal fields and also fields approaching blindness

Pattern standard deviation CANNOT be used for…

Staging disease (because approaches 0 in health and in severe disease)

What is the Octopus equivalent of the pattern standard deviation?

Corrected Comparison and Corrected Probabilities

What is the glaucoma hemifield test?

Splits the superior and inferior fields each into 5 zones and compares pattern deviations between superior and inferior (b/c in glaucoma will often see a difference in superior vs inferior field)

How is glaucoma hemifield test staged?

Within normal limits (WNL)

Outside normal limits

Borderline

Overall reduction/overall abnormally sensitive

What designates “outside normal limits” for glaucoma hemifield?

When <1% of patients with the given difference b/n superior and inferior were found to be normal

What is visual field index?

Like the mean deviation, but taken from the pattern deviation plot instead of total deviation plot (still puts more weight at the central points)

Measured as a PERCENTAGE where 100% is normal and approaches 0% with blindness

What global indice of field loss is used to indicate progression on the guided progression analysis?

Visual field index (VFI)

What is the guided progression analysis (GPA)?

Measures change in VFs over time using…

• Event Analysis

• Trend Analysis

Event analysis in the GPA shows…

Shows if the VF is significantly worse than baseline or not to indicate the likelihood of progression