ANSI Standards

The ANSI standards below are from 2015 and are subject to change. The guides are based off of ANSI Z80.1-2015.

SV & MF Lenses

  
    Meausure
     Sphere Power
     Tolerance
  
    Sphere Power
    0.00 to +/- 6.50
     +/- 0.13 D
  
    Greater than +/- 6.50
    2%
  
     Cylinder Power
    0.00 to +/- 2.00 D
    +/- 0.13 D
  
    +/-2.00 to 4.50
    +/- 0.15
  
     Greater than +/-4.50
    4%
  
    Cylinder Axis
    0.00 to 0.25
    014 Degrees
    
      0.25 to 0.50
      007 Degrees
  
  0.50 to 0.75
  005 Degrees
  
    0.75 to 1.50
    003 Degrees
  
    Greater than 1.50
    002 Degrees
  
    Add Power
    Up to +4.00
    +/- 0.12 D
    
  Above +4.00 
  +/- 0.18 D

This section tells us that a lens that has a Dioptic power up to plus or minus 6.50 can only be off by 0.13 Diopters. For example, a lens with an RX of -3.00 (between +6.50 and -6.50) that came in as -3.25 is not within ANSI standards. The tolerable range for a -3.00 lens would be -2.87 to -3.13 Diopters. Anything outside of this range would not qualify as passing ANSI standards.

If an RX is great than 6.50 Diopters of power then the tolerance switches to a percentage. Any difference greater than 2% of the dioptic power does not pass ANSI standards.

PRISM

  
    Meausure
     Sphere Power
     Tolerance
  
   Unmounted Prism & PRP
    0.00 to 3.37 
    0.33 Δ
  
    Greater than +/- 3.37
    1 mm
  
     Vertical Prism Imbalance
    ≥ 0.00 D, ≤ ±3.37 D
    ±0.33 Δ Total
  
     Greater than +/- 3.37
    1 mm
  
    Horizontal Prism Imbalance
     ≥ 0.00 D, ≤ ±2.75 D
    0.67 Δ Total
  
     Greater than +/- 2.75
    2.5 mm total

Segment

  
    Meausure
     Tolerance
  
   Vertical Segment Height
    +/- 1.0 mm each 
  
     Vertical Segment Difference
    1 mm difference
  
    Horizontal Segment Location
     +/- 2.5 mm
  
     Horizontal Segment Tilt
    +/- 2.0 degrees

Progressive Lens Designs

  
    Meausure
     Sphere Power
     Tolerance
  
    Sphere Power
    0.00 to +/- 8.00
     +/- 0.16 D
  
    Greater than +/- 8.00
    2%
  
     Cylinder Power
    0.00 to +/- 2.00 D
    +/- 0.16 D
  
    +/-2.00 to 3.50
    +/- 0.18
  
     Greater than +/-3.50
    5%
  
    Cylinder Axis
    0.00 to 0.25
    014 Degrees
    
      0.25 to 0.50
      007 Degrees
  
  0.50 to 0.75
  005 Degrees
  
    0.75 to 1.50
    003 Degrees
  
    Greater than 1.50
    002 Degrees
  
    Add Power
    Up to +4.00
    +/- 0.12 D
    
  Above +4.00 
  +/- 0.18 D

Please pay careful attention to the differences located in the Sohere power ranges, tolerance as well as the CYL power ranges and tolerances associated.

Ranges and tolerances for the AXIS and the ADD power are the same as in the SV/MF lenses.

  
    Meausure
     Sphere Power
     Tolerance
  
   Unmounted Prism & PRP
    0.00 to 3.37 
    0.33 Δ
  
    Greater than +/- 3.37
    1 mm
  
     Vertical Prism Imbalance
    ≥ 0.00 D, ≤ ±3.37 D
    ±0.33 Δ Total
  
     Greater than +/- 3.37
    1 mm
  
    Horizontal Prism Imbalance
     ≥ 0.00 D, ≤ ±3.37 D
    0.67 Δ Total
  
     Greater than +/- 3.37
    1.0 mm total

Again, please pay attention to the differences in ranges and tolerances here compared to SV/MF lens designs. Horizontal Prism Imbalance changes in Range and in tolerance.

  
    Meausure
     Tolerance
  
   Vertical Segment Height
    +/- 1.0 mm each 
  
     Vertical Segment Difference
    1 mm difference
  
    Horizontal Fitting Point Location
     +/- 1.0 mm
  
     Horizontal Axis Tilt
    +/- 2.0 degrees

More Tolerances

  
    Meausure
     Tolerance
  
   Center Thickness
    +/- 0.3 mm 
  
     Base Curve
    +/- 0.75
  
    Segment Size
     +/- 0.5 mm
  
     Warpage
    1.00 D