ABO NOCE Practice Test

For cylinder power of 0.50-0.75, what is the axis power tolerance?

1. 2°

2. 5°

3. 3°

4. 7°

The correct answer is: 5°

The axis power tolerance for cylinder power within the range of 0.50 to 0.75 typically falls within the 5° range. This tolerance level is established to provide adequate precision in the prescription of lenses for patients requiring cylinder correction. In the context of eyewear prescriptions, a cylinder power indicates the degree of astigmatism correction needed, and the axis describes the orientation of that correction. Having a 5° tolerance means that adjustments can be made within that degree range without significantly affecting the quality of vision correction. This level of tolerance is crucial for ensuring that the cylinder's orientation is closer to the optimal alignment for effective vision correction. Other tolerances, such as 2°, 3°, or 7°, would not provide the same balance between precision and practicality. The 5° range is thus widely accepted in the field, reflecting a consensus on the tolerable deviations for cylinder axes in this power range.