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ANSI Standards
ANSI Z80.1 tolerances and quality standards for ophthalmic lenses.
ANSI Z80.1 Overview
ANSI Z80.1 establishes tolerances for prescription ophthalmic lenses.
Covers: Sphere power, cylinder power, axis, add power, prism, segment placement, impact resistance, surface quality.
Verification: Opticians use a lensometer to verify sphere, cylinder, axis, prism, and add power.
Power and Axis Tolerances
Sphere Power Tolerance:
| Power Range | Tolerance |
|---|---|
| 0.00 to ±6.50 D | ±0.13 D |
| Above ±6.50 D | ±0.15 D |
Cylinder Axis Tolerance:
| Cylinder Power | Axis Tolerance |
|---|---|
| 0.00 to 0.25 D | ±14° |
| 0.25 to 0.50 D | ±7° |
| 0.50 to 0.75 D | ±5° |
| 0.75 to 1.50 D | ±3° |
| Above 1.50 D | ±2° |
Higher cylinder powers have tighter axis tolerances.
Prism, Add, and Other Tolerances
Prism Tolerance: ±0.33Δ per lens
Add Power Tolerance:
| Add Power | Tolerance |
|---|---|
| Up to +4.00 D | ±0.12 D |
| Above +4.00 D | ±0.18 D |
Segment Placement: ±1.0mm horizontal and vertical
Impact Resistance: FDA drop-ball test — 5/8-inch steel ball from 50 inches.
Surface Quality: Free of visible defects in the central 30mm zone.