AMERICAN NATIONAL STANDARD

AMERICAN NATIONAL STANDARD Z80.1-1999

**Table 1 – Tolerance on distance refractive power**
Absolute power of meridian of highest power	Tolerance on meridian of highest power	Cylinder > 0.00 D < 2.00 D	Cylinder > 2.00 D < 4.50 D	Cylinder > 4.50 D
From 0.00 up to 6.50 D	± 0.13 D	± 0.13 D	± 0.15 D	± 4%
Above 6.50 D	± 2%	± 0.13 D	± 0.15 D	± 4%

**Table 2 – Tolerance on the direction of cylinder axis**
Nominal value of the cylinder power (D)	> 0.00 D < 0.37 D	> 0.37 D > 0.75 D	> 0.75 D < 1.50 D	> 1.50 D
Tolerance of the axis (degrees)	± 7°	± 5°	± 3°	± 2°

**Table 3 – Tolerance on addition power for multifocal and progressive addition lenses**
Nominal value of addition power (D)	< 4.00 D	> 4.00 D
Nominal value of the tolerance on the addition power (D)	± 0.12 D	± 0.18 D

**Table 4 – Tolerance on Prism Reference Point Location and Prismatic Power**
Single Vision and MultifocalLenses	Vertical 0.00 to ±3.375 D	Vertical > ± 3.375 D	Horizontal 0.00 to ±2.75 D	Horizontal > ± 2.75 D
Tolerance	0.33 delta	1.0 MM	0.67 delta	2.5 MM
Progressive AdditionLenses	Vertical 0.00 to ±3.375 D	Vertical > ± 3.375 D	Horizontal 0.00 to ±3.75 D	Horizontal > ± 3.75 D
Tolerance	0.33 delta	1.0 MM each reference point	0.67 delta	1.0 MM each reference point

5. Base Curve Tolerance

When specified, the base curve shall be supplied within ± 0.75 D.

6. Center Thickness Tolerance

The center thickness shall be measured at the prism reference point of the convex surface. It shall not deviate from the nominal value by more than ± 0.3mm.

7. Segment Size Tolerance for Multifocals

The segment dimensions (width, depth, and intermediate depth) shall not deviate from the nominal value by more than ± 0.5mm. The difference between the segment dimensions (width, depth, and intermediate depth) in the mounted pair shall not exceed 0.7mm.

8. Segment Vertical Location and Fitting Cross Vertical Location

The segment height shall match within ± 1.0mm of specification. In the case of progressive addition lenses, the fitting cross height shall be within ± 1.0mm of specification. The difference between the segment height or fitting cross height in the mounted pair shall not exceed 1.0mm.

9. Segment Horizontal Location and Fitting Cross Horizontal Location

The distance between geometric centers of the segments in the mounted pair shall be within ± 2.5mm of the specified near interpupillary distance. The inset in both lenses shall appear symmetrical and balanced unless monocular insets are specified. In the case of progressive addition lenses, the near reference point is set by the lens design. The fitting cross location in progressive lenses shall be within ± 1.0mm of the specified monocular interpupillary distance for that lens.

10. Localized Errors

Localized power errors or aberrations caused by waves, warpage or internal defects, which are detected by visual inspection, are permissible if no measurable or gross focimeter target element distortion or blur is found when the localized area is examined with a focimeter. Areas outside a 30-mm diameter from the distance reference point, or within 6 mm from the edge, need not be tested for local power errors or aberrations. Progressive addition lenses are exempt from this requirement.

11. Prescription Impact-resistant Dress Eyewear Lenses

All lenses must conform to the impact resistance requirements of Title 21, Code of Federal Regulations, 801.410 (CFR 801.410). Laminated, plastic and raised-ledge multifocal lenses may be certified by the manufacturer as conforming to the initial design testing or statistically significant sampling as specified by CFR 801.410. All monolithic (not laminated) glass lenses shall be treated to be impact resistant.