ABO NOCE Basic Opticianry ANSI Z80.1 Standards and Tolerances 3 — Questions and Answers
Question 1: A finished single-vision lens is measured and found to have 0.40Δ of unwanted horizontal prism at the MRP. According to ANSI Z80.1, this lens:
- Is within tolerance for all prescriptions
- Exceeds tolerance for prescriptions ±3.37 D or less (Correct answer)
- Is only acceptable for high-power prescriptions
- Meets tolerance because horizontal prism has a wider allowance
Correct answer: Exceeds tolerance for prescriptions ±3.37 D or less
ANSI Z80.1 allows only 0.33Δ of horizontal prism at the major reference point for prescriptions up to ±3.37 D, so 0.40Δ exceeds tolerance.
Question 2: For a bifocal lens, ANSI Z80.1 specifies the vertical prism imbalance between the two segment optical centers should not exceed:
- 0.25Δ
- 0.33Δ
- 0.50Δ (Correct answer)
- 0.75Δ
Correct answer: 0.50Δ
ANSI Z80.1 allows up to 0.50Δ of vertical prism imbalance between the two segments of a bifocal lens.
Question 3: What does ANSI Z80.1 define as the 'major reference point' (MRP) on a finished lens?
- The geometric center of the lens blank
- The point where prism and power are verified (Correct answer)
- The optical center of the distance zone only
- The point coinciding with the pupil in primary gaze
Correct answer: The point where prism and power are verified
The MRP is the verification point on the lens where the specified prism and power are measured and confirmed.
Question 4: According to ANSI Z80.1, what is the allowable tolerance for base curve on an uncut lens?
- ±0.06 D
- ±0.12 D
- ±0.25 D
- ±0.75 D (Correct answer)
Correct answer: ±0.75 D
ANSI Z80.1 allows a base curve tolerance of ±0.75 D for uncut finished lenses.
Question 5: Under ANSI Z80.1, what is the tolerance for vertical prism at the MRP when the prescription includes no prescribed prism?
- 0.25Δ (Correct answer)
- 0.33Δ
- 0.50Δ
- 1.00Δ
Correct answer: 0.25Δ
ANSI Z80.1 limits unwanted vertical prism to 0.25Δ at the MRP when no prism is prescribed.
Question 6: When ANSI Z80.1 refers to 'surface quality,' which defect is specifically addressed?
- Lens tint uniformity
- Scratches, bubbles, and inclusions visible under diffuse light (Correct answer)
- Anti-reflective coating delamination
- Edge chipping during glazing
Correct answer: Scratches, bubbles, and inclusions visible under diffuse light
ANSI Z80.1 surface quality standards address cosmetic defects such as scratches, bubbles, and inclusions that could affect optical performance or appearance.
Question 7: A lens with a prescription of -9.00 D sphere: what sphere power tolerance does ANSI Z80.1 apply?
- ±0.06 D
- ±0.12 D
- ±0.13 D
- ±0.18 D (Correct answer)
Correct answer: ±0.18 D
For lens powers exceeding ±6.50 D, ANSI Z80.1 applies a tolerance of ±2% of the prescribed power; 2% of 9.00 D = 0.18 D.
ABO NOCE Basic Opticianry ANSI Z80.1 Standards and Tolerances 3
A finished single-vision lens is measured and found to have 0.40Δ of unwanted horizontal prism at the MRP.
According to ANSI Z80.1, this lens: