ABO NOCE Basic Opticianry ANSI Z80.1 Standards and Tolerances 5 — Questions and Answers
Question 1: When a lens has a prescribed cylinder of -1.25 D, ANSI Z80.1 requires the cylinder power to be within:
- ±0.06 D
- ±0.09 D
- ±0.12 D (Correct answer)
- ±0.25 D
Correct answer: ±0.12 D
ANSI Z80.1 specifies a cylinder power tolerance of ±0.12 D for cylinder powers up to ±2.00 D.
Question 2: ANSI Z80.1 defines 'fitting point' on a progressive lens as:
- The optical center of the distance zone
- The point that aligns with the pupil in primary gaze during fitting (Correct answer)
- The geometric center of the lens blank
- The midpoint of the progressive corridor
Correct answer: The point that aligns with the pupil in primary gaze during fitting
The fitting point on a PAL is the manufacturer-designated mark that should align with the patient's pupil center in primary gaze during the fitting process.
Question 3: A dispensed pair of single-vision lenses shows 0.60Δ of induced vertical imbalance between the two lenses at the MRP. According to ANSI Z80.1, this is:
- Acceptable for all prescriptions
- Acceptable only if no prism was prescribed
- Unacceptable; vertical tolerance is 0.25Δ per lens (Correct answer)
- Acceptable because the combined tolerance allows 0.75Δ
Correct answer: Unacceptable; vertical tolerance is 0.25Δ per lens
ANSI Z80.1 limits unwanted vertical prism to 0.25Δ per lens at the MRP, so 0.60Δ of total imbalance far exceeds the per-lens tolerance.
Question 4: Under ANSI Z80.1, what is the purpose of the 'reference point' on a progressive addition lens?
- To mark where the add power measurement is taken (Correct answer)
- To indicate the manufacturer's recommended fitting cross
- To show where anti-reflective coating begins
- To identify the optical center of the near zone
Correct answer: To mark where the add power measurement is taken
The near reference point on a PAL is the designated location where the specified add power is measured and verified.
Question 5: ANSI Z80.1 specifies that the segment of a flat-top bifocal must be within what horizontal tolerance of the specified position?
- ±0.5 mm
- ±1.0 mm (Correct answer)
- ±1.5 mm
- ±2.0 mm
Correct answer: ±1.0 mm
ANSI Z80.1 requires horizontal segment positioning to be within ±1.0 mm of the specified location.
Question 6: When verifying prescribed prism of 1.50Δ base in, ANSI Z80.1 allows a tolerance of:
- ±0.12Δ
- ±0.25Δ (Correct answer)
- ±0.37Δ
- ±5% of prescribed amount
Correct answer: ±0.25Δ
For prescribed prism of 2.00Δ or less, ANSI Z80.1 allows a tolerance of ±0.25Δ in any meridian.
Question 7: Which of the following would ANSI Z80.1 classify as a cosmetic defect requiring rejection of a finished lens?
- A single pinpoint bubble located 15 mm from the optical center
- Multiple scratches within the central 30 mm optical zone visible under diffuse illumination (Correct answer)
- Slight edge tinting from heat treatment
- A minor variation in base curve of ±0.25 D
Correct answer: Multiple scratches within the central 30 mm optical zone visible under diffuse illumination
ANSI Z80.1 surface quality requirements reject lenses with multiple defects such as scratches or bubbles within the central optical zone that are visible under diffuse light.
ABO NOCE Basic Opticianry ANSI Z80.1 Standards and Tolerances 5
When a lens has a prescribed cylinder of -1.25 D, ANSI Z80.1 requires the cylinder power to be within: