Which device is typically used for testing a semicircular arc around the center of vision?

Which device is typically used for testing a semicircular arc around the center of vision?

• A. Harrington Flocks Screener
• B. Arc Perimeter
• C. Amsler Grid
• D. Tangent Screen

Answer: (B)

Testing the semicircular arc around the center of vision relies on perimetry to map sensitivity as you fixate straight ahead. An arc perimeter is built to present light stimuli along a curved path centered on the fixation point, allowing the clinician to sample thresholds at multiple points around that arc efficiently. This setup is especially useful for detecting arcuate or nerve-fiber–bundle patterns of loss that commonly appear in conditions like glaucoma, where defects trace a semicircular pathway around the center. The patient maintains fixation and indicates when they see a stimulus, and the collected responses create a profile of sensitivity along that semicircular arc. This approach differs from the Amsler grid, which screens central vision for metamorphopsia on a flat grid and focuses on a small central area rather than an arc around fixation. The Tangent Screen projects stimuli on a flat plane to map a broader field but does not specifically target a semicircular arc around the center. The Harrington Flocks Screener is a general screening tool and not the arc-focused method used to test along a semicircular arc around the center of vision.

Testing the semicircular arc around the center of vision relies on perimetry to map sensitivity as you fixate straight ahead. An arc perimeter is built to present light stimuli along a curved path centered on the fixation point, allowing the clinician to sample thresholds at multiple points around that arc efficiently. This setup is especially useful for detecting arcuate or nerve-fiber–bundle patterns of loss that commonly appear in conditions like glaucoma, where defects trace a semicircular pathway around the center. The patient maintains fixation and indicates when they see a stimulus, and the collected responses create a profile of sensitivity along that semicircular arc.

This approach differs from the Amsler grid, which screens central vision for metamorphopsia on a flat grid and focuses on a small central area rather than an arc around fixation. The Tangent Screen projects stimuli on a flat plane to map a broader field but does not specifically target a semicircular arc around the center. The Harrington Flocks Screener is a general screening tool and not the arc-focused method used to test along a semicircular arc around the center of vision.