CPO FREE CPO Visual Field Testing (Perimetry) Questions and Answers 2

Question 1

A visual field printout shows a dense superior defect that appears arcuate in shape on the pattern deviation plot. However, the grayscale plot shows a distinct 'cloverleaf' or quadrantanopic pattern. What is the most likely cause of this specific artifact?

Accepted Answer

Patient fatigue and inattention, leading to a high number of false negatives.

Answer

The 'cloverleaf' pattern is a classic sign of high false negatives. This occurs when a patient becomes fatigued or inattentive during the test and stops responding. Because the testing algorithm often checks the four central quadrant points first before spiraling outwards, the patient may respond initially but then fail to respond to dimmer or more peripheral stimuli, creating a pattern where only the central points in each quadrant are seen.

Question 2

A patient with a known pituitary adenoma is undergoing visual field testing. Which of the following less common visual field defects would most specifically indicate that the tumor is exerting pressure on the *uncrossed* nasal retinal fibers at the optic chiasm?

Accepted Answer

Binasal Hemianopia

Answer

Binasal hemianopia, the loss of the inner (nasal) halves of the visual field in both eyes, is a rare defect. It can be caused by pressure on the uncrossed temporal nerve fibers in both optic nerves, often from conditions like hydrocephalus or, in some cases, bilateral internal carotid artery aneurysms compressing the nerves from the side. While bitemporal hemianopia is classic for chiasmal compression, binasal defects point to pressure on the lateral, uncrossed fibers.

Question 3

Kinetic perimetry, such as Goldmann perimetry, is preferred over standard automated static perimetry in which of the following clinical scenarios?

Accepted Answer

Mapping the peripheral visual field boundaries in a patient with advanced retinitis pigmentosa.

Answer

Kinetic perimetry, which uses a moving stimulus of a set size and brightness, excels at mapping the outer boundaries (isopters) of the visual field. It is particularly useful for assessing peripheral vision in conditions like advanced retinitis pigmentosa, evaluating complex neuro-ophthalmic defects, or for patients who cannot perform static perimetry well. Static perimetry is more sensitive for detecting and quantifying the depth of scotomas in early glaucoma or for central field defects.

Question 4

When performing perimetry on a patient who is wheelchair-bound and has difficulty maintaining a stable head position in a conventional automated perimeter, which modification is most critical to obtaining a reliable test?

Accepted Answer

Utilizing a virtual reality (VR) headset-based perimeter.

Answer

Conventional perimeters pose significant accessibility challenges for patients with mobility issues or those who cannot maintain the required posture. A virtual reality (VR) headset-based perimeter is an ideal solution as it eliminates the need for a chin/forehead rest, allows the patient to remain in their wheelchair, and can be performed in a reclined or comfortable position, greatly enhancing stability and reliability for this patient population.

Question 5

The Visual Field Index (VFI) is a global index on a Humphrey printout that stages the total amount of visual field loss. How does it primarily differ from the Mean Deviation (MD)?

Accepted Answer

VFI is less affected by generalized depression, such as from a cataract, than MD.

Answer

The Visual Field Index (VFI) is designed to be less sensitive to generalized depressions in the visual field, such as those caused by cataracts. It is a staged percentage (100% is normal, 0% is perimetrically blind) that gives greater weight to central points and is derived from the pattern deviation plot to minimize the effect of media opacity. Mean Deviation (MD), in contrast, reflects the overall mean departure from the age-corrected normal field and is significantly affected by cataracts.

(CPO) Certified Paraoptometric Practice Test

(CPO) Certified Paraoptometric Practice Test

CPO FREE CPO Visual Field Testing (Perimetry) Questions and Answers 2