Which statement accurately describes the basic relationship between prism diopters and degrees of visual field used in the material?

Which statement accurately describes the basic relationship between prism diopters and degrees of visual field used in the material?

• A. 2 prism diopters correspond to 1 degree of visual field
• B. 1 prism diopter corresponds to 1 degree
• C. 3 prism diopters correspond to 0.5 degree
• D. 4 prism diopters correspond to 2 degrees

Answer: (A)

Prism diopters quantify angular deviation of light; by definition, 1 prism diopter bends light enough that at a distance of 1 meter the light would shift by 1 centimeter. To translate that into an angular measure, use the small-angle relationship: angle in radians ≈ opposite/adjacent = 1 cm / 100 cm = 0.01 radians. Converting to degrees gives about 0.01 × (180/π) ≈ 0.57 degrees. So about 2 prism diopters produce roughly 1 degree of visual angle. This is the conversion used in the material. The other statements don’t match the approximate conversion: 1 PD is ~0.57 degrees, 3 PD is ~1.7 degrees, and 4 PD is ~2.3 degrees, not the exact values proposed.

Prism diopters quantify angular deviation of light; by definition, 1 prism diopter bends light enough that at a distance of 1 meter the light would shift by 1 centimeter. To translate that into an angular measure, use the small-angle relationship: angle in radians ≈ opposite/adjacent = 1 cm / 100 cm = 0.01 radians. Converting to degrees gives about 0.01 × (180/π) ≈ 0.57 degrees. So about 2 prism diopters produce roughly 1 degree of visual angle. This is the conversion used in the material. The other statements don’t match the approximate conversion: 1 PD is ~0.57 degrees, 3 PD is ~1.7 degrees, and 4 PD is ~2.3 degrees, not the exact values proposed.