ABO NOCE Basic Opticianry ANSI Z80.1 Standards and Tolerances 4 — Questions and Answers
Question 1: ANSI Z80.1 cylinder axis tolerance for prescriptions with cylinder power less than 0.75 D is:
- ±2 degrees
- ±5 degrees (Correct answer)
- ±7 degrees
- No axis tolerance specified
Correct answer: ±5 degrees
When cylinder power is less than 0.75 D, ANSI Z80.1 allows a wider axis tolerance of ±5 degrees because small cylinder powers are less sensitive to axis error.
Question 2: According to ANSI Z80.1, progressive addition lenses must have their distance and near reference points verified within what horizontal tolerance of the specified position?
- ±0.5 mm
- ±1.0 mm (Correct answer)
- ±2.0 mm
- ±2.5 mm
Correct answer: ±1.0 mm
ANSI Z80.1 specifies that the horizontal position of the distance and near reference points on PALs must be within ±1.0 mm of the specified location.
Question 3: Which of the following best describes an 'optical center' as used in ANSI Z80.1 verification?
- The point of maximum plus power on the lens
- The point where a ray passes through the lens without deviation (Correct answer)
- The geometric center of the finished frame
- The prism reference point on a PAL
Correct answer: The point where a ray passes through the lens without deviation
The optical center is the point on a lens through which light passes without being deviated by prism, and it is the basis for MRP placement.
Question 4: Under ANSI Z80.1, what is the allowable tolerance for prescribed prism when the prescribed amount is greater than 2.00Δ?
- ±0.25Δ
- ±0.37Δ or 5% (whichever is greater) (Correct answer)
- ±0.50Δ
- ±1% of prescribed amount
Correct answer: ±0.37Δ or 5% (whichever is greater)
ANSI Z80.1 allows ±0.37Δ or 5% of the prescribed prism amount (whichever is greater) when prescribed prism exceeds 2.00Δ.
Question 5: ANSI Z80.1 requires that the segment height of a lined bifocal be within what vertical tolerance of the specified height?
- ±0.5 mm
- ±1.0 mm (Correct answer)
- ±1.5 mm
- ±2.0 mm
Correct answer: ±1.0 mm
ANSI Z80.1 specifies that lined bifocal segment height must be within ±1.0 mm of the specified height.
Question 6: Which lens type is NOT subject to the impact-resistance requirements referenced in ANSI Z80.1?
- Dress ophthalmic lenses
- Safety lenses (Correct answer)
- Sunglasses with no Rx
- Plano fashion eyewear
Correct answer: Safety lenses
Safety lenses are governed by ANSI Z87.1, a separate standard with stricter impact requirements than the dress ophthalmic lens standard Z80.1.
Question 7: For a PAL with a prescribed add of +2.50 D, the measured add is +2.67 D. According to ANSI Z80.1, this lens:
- Is within the ±0.14 D tolerance
- Exceeds the ±0.12 D tolerance (Correct answer)
- Is within tolerance because PAL add has a ±0.25 D allowance
- Exceeds tolerance only if the distance power is also off
Correct answer: Exceeds the ±0.12 D tolerance
The measured add deviates by +0.17 D from the prescribed +2.50 D, which exceeds the ANSI Z80.1 tolerance of ±0.12 D for add power.
ABO NOCE Basic Opticianry ANSI Z80.1 Standards and Tolerances 4
ANSI Z80.1 cylinder axis tolerance for prescriptions with cylinder power less than 0.75 D is: