Total prismatic effect calculation requires information from how many eyes?

Total prismatic effect calculation requires information from how many eyes?

• A. 2 eyes
• B. 1 eye
• C. Both eyes
• D. Invalid

Answer: (B)

Prismatic effect is the angular deviation light undergoes when it passes through a prism. When you’re calculating the total prismatic effect for a given viewing condition, you’re evaluating the effect within the optical path of one eye. The standard calculation is done eye by eye, so the data you need is from a single eye—the prism power and direction at that eye determine the total prismatic effect for that path. The other eye would have its own potential prismatic input, and binocular summation would require combining both eyes’ effects separately, but for this calculation you rely on information from one eye.

Prismatic effect is the angular deviation light undergoes when it passes through a prism. When you’re calculating the total prismatic effect for a given viewing condition, you’re evaluating the effect within the optical path of one eye. The standard calculation is done eye by eye, so the data you need is from a single eye—the prism power and direction at that eye determine the total prismatic effect for that path. The other eye would have its own potential prismatic input, and binocular summation would require combining both eyes’ effects separately, but for this calculation you rely on information from one eye.