9.12  Automated Visual Fields

• Name
• Age of patient
  • Age determines the likelihood of particular diseases. Results are compared against age-matched normal values
• Right eye or left eye
• Date of exam

i. Fixation monitor

• “Gaze/blindspot” means that both the gaze tracker and the blindspot have been used to detect fixation losses

ii. Fixation target

• “Central” = foveal

iii. Fixation losses

• The blindspot is mapped first. If the patient responds when this area of visual field is re-tested, it means that the patient has moved their eye. Fixation losses exceeding 20% may indicate a compromised test

iv. False Positive Errors

• Number of times the patient responds when no stimulus is present. False positive rates exceeding 15% may indicate a compromised test

v. False Negative Errors

• Number of times a patient fails to respond to a stimulus brighter than previously determined threshold value at that location. A high false negative rate may indicate fatigue, inattention or malingering

vi. Test Duration

• A lengthy test may suggest poor reliability

vii. Gaze Tracker

• Timeline of fixation behaviour. Upward deflection represents eye movements, downward deflection indicates gaze cannot be detected (e.g. blinks). Excessive periods of poor fixation may be associated with reduced reliability

• Usually Goldmann size III, but may be increased in advanced glaucoma

1. White stimulus (standard white-on-white)
2. Red stimulus. There is some evidence that this may be preferable for drug induced maculopathies.
3. Short-wavelength automated perimetry (SWAP) uses a blue stimulus on yellow background. Blue-on-yellow perimetry deficits are an early indicator of glaucomatous damage and may also be useful in detecting neuro-ophthalmologic deficits more readily than standard white-on-white

• Usually 31.5 apostilbs

1. SITA Standard™ (Swedish Interactive Threshold Algorithm). This is a mathematical model that produces a personalized test, allowing for faster testing with minimal compromise in accuracy compared with full threshold testing
2. SITA Fast™. This may be preferred if reliability is compromised by a long test in a slow patient
3. Full threshold

• Miotics may reduce sensitivity of tests

• Spectacle prescription used in the test

• Numeric sensitivity (dB) and gray scale graphical representation of visual field sensitivity with darker areas depicting lower sensitivity. The gray scale is often the least useful plot

• Indicative of a patient’s sensitivity compared to normal age-corrected sensitivities at each location. The numerical scale expresses this in decibels (lower than expected sensitivities are given negative values). The probability plot has progressive stippling representing whether the sensitivity at a particular location is worse than the lowest 0.5%, 1%, 2% and 5% of an age-matched normal population

• This is the most useful of all the plots, except in advanced visual field loss when even the best points are severely depressed. It indicates localized visual field loss by correcting for any generalized depression. A uniformly depressed total deviation and normal pattern deviation may indicate cataract; a normal total deviation and abnormal pattern deviation may indicate a “trigger-happy” patient

Glaucomatous visual field changes usually respect the horizontal midline. The Glaucoma Hemifield Test assesses the probability of glaucoma by comparing the superior and inferior visual fields. It should never be used alone to diagnose glaucoma. The result may be:

1. Outside Normal Limits
   1. If the sensitivity in at least 1 of 5 zones in the superior visual field are significantly different (p < 0.01) to those in the mirror-image inferior visual field
2. Borderline
3. General Depression of Sensitivity or Abnormally High Sensitivity
4. Within Normal Limits

A. Glaucomatous Patterns

1. Paracentral scotomas
2. Arcuate scotomas
3. Nasal steps

B. Neurological Patterns