4.1.2: Measures & verifies optical appliances

Question 1

What are the tolerances of focimetry? Accurate results within…

Answer 1

• +/- 0.25DS/SC for dioptric measurements
• Axis appropriate to cyl power:
  0 ≤ 0.50DC +- 9°
  0 > 0.50DC ≤ 0.75DC +- 6°
  0 > 0.75DC ≤ 1.50DC +- 4°
  0 > 1.50DC +- 3°
• Centres 1mm tolerance

Question 2

Tolerances of SV and MF lenses?

Question 3

Tolerances of primary reference point of power-variation lenses?

Question 4

Tolerance on direction of cyl axis?

Question 5

Tolerance on add power?

Answer 5

≤ 4.00 - +-0.12
> 4.00 - +-0.18

Question 6

Why should you compare lenses to tolerance?

Answer 6

to ensure a standard of all lenses produced so pxs do not end up with wrong Rxs

Question 7

What do you do if you are under/over tolerance of the lenses?

Answer 7

see how much under or over tolerance
needs to be reordered

Question 8

What are the positioning tolerance on Bif-Var?

Answer 8

vertical: within 1mm
horizontal: within 1mm
tilt: no more than 2° from horizontal