At what angle does the ANSI standard classify the cylinder axis for measurements from 0 to .25D?

The ANSI (American National Standards Institute) standard for optical measurements specifies that the classification of the cylinder axis for lower values of cylinder power, specifically from 0 to 0.25 diopters, should be within a certain tolerance. According to the ANSI standard, this tolerance is set to 14 degrees.

This means that when measuring the axis of a cylindrical lens with a power less than or equal to 0.25D, any deviation of the indicated axis can be accepted within a range of 14 degrees. This standard ensures consistent and reliable measurement practices within the field of optometry and optical dispensing, particularly when dealing with lower cylinder powers where precision in alignment can be crucial for patient comfort and visual acuity.

In this context, a tolerance of 3, 5, or 10 degrees would not meet the standard requirements for this particular range, indicating that these values represent insufficient allowances for the variance that can occur in practical applications and may lead to suboptimal visual correction. Thus, 14 degrees is the correct answer that aligns with the ANSI standard for this measurement range.