Reference
ANSI Z80.1 tolerances
The values below are as commonly published in opticianry training materials for finished single-vision lenses. The standard is revised periodically: verify the edition in force at your laboratory before applying any figure to real work.
Cylinder axis tolerance by cylinder power
| Cylinder power | Axis tolerance |
|---|---|
| 0.25 D or less | +/- 14 degrees |
| over 0.25 to 0.50 D | +/- 7 degrees |
| over 0.50 to 0.75 D | +/- 5 degrees |
| over 0.75 to 1.50 D | +/- 3 degrees |
| over 1.50 D | +/- 2 degrees |
Boundaries land in the wider bracket: exactly 1.50 D allows 3 degrees and exactly 0.75 D allows 5 degrees. Axis deviation wraps the 180 degree scale, so 178 against 002 is 4 degrees, not 176.
Power tolerances
| Parameter | Range | Tolerance |
|---|---|---|
| Sphere power | through +/- 6.50 D | +/- 0.13 D |
| above +/- 6.50 D | +/- 2 percent | |
| Cylinder power | through 2.00 D | +/- 0.13 D |
| over 2.00 to 4.50 D | +/- 0.15 D | |
| above 4.50 D | +/- 4 percent |
Check a job
The tolerance checker applies this whole table to an ordered-versus-measured pair for both eyes and reports each parameter separately.
Frequently asked questions
Which edition of ANSI Z80.1 do these values come from?
These are the values as commonly published in opticianry training materials. The standard is revised periodically, so verify the edition in force at your laboratory before applying any figure to real work.
Why does the axis allowance shrink as cylinder grows?
The blur induced by an axis error is proportional to the cylinder power, so the same visual quality demands a tighter axis on a stronger cylinder.