Visual Field Testing (Perimetry) Flashcards

A Humphrey Visual Field (HVF) printout shows a normal total deviation plot but a significant inferior depression on the pattern deviation plot. The Glaucoma Hemifield Test (GHT) is flagged as 'Abnormally high sensitivity' and the mean deviation (MD) is +2.5 dB. What is the most likely cause of these findings?

Answer: The patient was 'trigger-happy,' pressing the response button excessively and randomly.

A 'trigger-happy' or false-positive-prone patient often produces a visual field with abnormally high sensitivity. The normal total deviation with an abnormal pattern deviation, a positive Mean Deviation, and the 'Abnormally high sensitivity' GHT flag are classic indicators of excessive button pressing, not true pathology.

While automated static perimetry is standard for most glaucoma follow-ups, in which of the following scenarios would kinetic perimetry, such as Goldmann, be more clinically useful?

Answer: A patient with severe central vision loss who can only see in the far periphery.

Kinetic perimetry, which uses a moving stimulus of a set size and brightness, is particularly effective for mapping the outer boundaries of the visual field and characterizing the remaining islands of vision in patients with very advanced field loss or only peripheral vision remaining. Static perimetry can be less effective in these cases as the central field it typically tests may be entirely gone.

On a Guided Progression Analysis (GPA) printout for a glaucoma patient, what does a solid, fully-darkened triangle at a specific test point signify?

Answer: The point has shown statistically significant deterioration on three consecutive follow-up tests.

The GPA software uses a system of symbols to indicate potential progression. An open triangle indicates initial deterioration. A half-filled triangle indicates deterioration confirmed on a second consecutive test. A solid, fully-darkened triangle signifies 'likely progression,' meaning the same point has shown statistically significant worsening on three consecutive examinations compared to the baseline.

A patient's visual field report describes a 'relative scotoma' in the superior arcuate region. What does this term mean?

Answer: An area where dimmer or smaller light stimuli cannot be seen, but brighter or larger ones can.

A relative scotoma is an area of reduced sensitivity within the visual field. Unlike an absolute scotoma where nothing can be seen, a relative scotoma is characterized by the inability to see finer or dimmer stimuli, while brighter or larger stimuli are still detectable.

The Visual Field Index (VFI) is a global index used to track glaucoma progression. What is a key feature of how the VFI is calculated?

Answer: It gives greater weight to central points compared to peripheral points.

The Visual Field Index (VFI) is an age-adjusted percentage of visual function, with 100% being normal. A key feature of its calculation is that it gives more weight to the central points of the visual field, reflecting the greater functional importance of central vision for daily activities.

During a visual field test, the technician notes the patient seems to be losing concentration and periodically falling asleep. The resulting printout shows a distinct, four-leaf clover pattern of dense defects. This artifact is most likely caused by:

Answer: Patient fatigue and a delayed response time to stimuli.

The 'cloverleaf' pattern is a classic artifact caused by patient fatigue or inattention. The patient responds to the initial, easily seen stimuli but then loses focus or dozes off, failing to respond to subsequent stimuli in all quadrants. As the test progresses, they may re-engage, creating a pattern that spares the initial test areas but shows dense loss elsewhere.