American Board of Opticianry (ABO) Practice Test

What is the function of Prentice's Rule?

1. Calculate prismatic effect

2. Characteristic of a minus lens

3. Power times 0.5

4. Measures vertex distance

The correct answer is: Calculate prismatic effect

Prentice's Rule is a mathematical formula used to calculate the prismatic effect, or the displacement of light, caused by lenses in eyewear. It takes into account the power of the lens and the distance between the optical center and the patient's pupil. This rule is used to determine the correct lens strength and placement to correct for conditions such as double vision. Options B, C, and D are incorrect as they do not relate to the function of Prentice's Rule. While a minus lens is a characteristic of Prentice's Rule, it is not the intended function. Option C is also incorrect as the formula does not include multiplying the power by 0.5. And finally, Prentice's Rule does not measure vertex distance, which is the distance from the back surface of the lens to the front surface of the eye.