Free CPO Visual Field Testing (Perimetry) Questions and Answers 1 — Questions and Answers
Question 1: What is the primary purpose of visual field testing (perimetry)?
- To measure the refractive error of the eye
- To assess the health of the cornea
- To map a patient's peripheral and central vision (Correct answer)
- To determine the intraocular pressure
Correct answer: To map a patient's peripheral and central vision
Perimetry is a diagnostic test that systematically maps the full extent of a patient's vision, including central and peripheral fields. It is crucial for detecting, diagnosing, and monitoring diseases that affect the optic nerve and visual pathways, such as glaucoma, strokes, and brain tumors.
Question 2: During automated perimetry, what is the most common method the machine uses to ensure the patient is maintaining steady fixation?
- Asking the patient periodically if they are looking at the target
- Using a chin strap to hold the head still
- Presenting stimuli in the physiological blind spot (Correct answer)
- Tracking the pupil with a video camera
Correct answer: Presenting stimuli in the physiological blind spot
The perimeter periodically projects a light stimulus into the location of the patient's physiological blind spot, which corresponds to the optic nerve head. If the patient sees and responds to this stimulus, it indicates they have moved their eye and are no longer fixating on the central target. This is known as the Heijl-Krakau method.
Question 3: A visual field test where the stimulus light is stationary but varies in brightness to find the dimmest light a patient can see at each location is known as:
- Kinetic perimetry
- Static perimetry (Correct answer)
- Confrontation visual field testing
- Amsler grid testing
Correct answer: Static perimetry
Static automated perimetry is the most common type of visual field testing today. It involves presenting light stimuli of varying intensities at fixed locations throughout the visual field to determine the threshold of vision at each point. Kinetic perimetry, in contrast, uses a moving stimulus of a fixed brightness.
Question 4: Which of the following visual field defects is most characteristically associated with early to moderate glaucoma?
- Bitemporal hemianopia
- Central scotoma
- Arcuate scotoma (Correct answer)
- Altitudinal defect
Correct answer: Arcuate scotoma
Glaucoma typically damages the retinal nerve fibers that arch from the optic nerve superiorly and inferiorly around the macula. This damage results in an arc-shaped (arcuate) scotoma, or blind spot, in the visual field that respects the horizontal midline.
Question 5: What is the most critical instruction to give a patient before starting an automated visual field test?
- 'Try not to blink during the entire test.'
- 'Press the button for every light you see, no matter how dim, while always looking at the central light.' (Correct answer)
- 'Try to find the lights by looking around the bowl.'
- 'Only press the button for the very bright lights.'
Correct answer: 'Press the button for every light you see, no matter how dim, while always looking at the central light.'
Maintaining steady fixation on the central target is paramount for an accurate and reliable visual field test. If the patient looks around for the lights, the test will not be mapping their peripheral vision correctly, rendering the results invalid. Blinking is normal and encouraged to keep the eye moist.
Question 6: On a Humphrey Visual Field printout, a high number of 'False Positives' indicates that the patient was:
- Not paying attention
- Moving their eye off the fixation target
- Pressing the response button too often or randomly (Correct answer)
- Failing to see bright stimuli they should have seen
Correct answer: Pressing the response button too often or randomly
A false positive error is recorded when the patient presses the response button during a period when no stimulus was presented. A high number of these errors often indicates the patient is anxious or 'trigger-happy,' pressing the button in anticipation of a light, which can make the test results appear better than they actually are.
Free CPO Visual Field Testing (Perimetry) Questions and Answers 1
What is the primary purpose of visual field testing (perimetry)?