Verification of Lenses

lens with the highest power in the 90-degree meridian

which lens should you start with when verifying spectacles?

±0.13D

what is the tolerance for a sphere power of up to ±6.50D?

±2.00% of the power

what is the tolerance for a sphere power of above ±6.50D?

0.13D

what is the tolerance for a cyl power of 2.00D or less?

0.15

what is the tolerance for a cyl power of 2.00D-4.50D?

4% of the power

what is the tolerance for a cyl power above 4.50D?

2deg

what is the tolerance for cyl axis if the cylinder power is 1.75D or greater?

3deg

what is the tolerance for cyl axis if the cylinder power is 1.00, 1.25, or 1.50D?

5deg

what is the tolerance for cyl axis if the cylinder power is 0.75D?

7deg

what is the tolerance for cyl axis if the cylinder power is 0.50D?

14deg

what is the tolerance for cyl axis if the cylinder power is 0.25D?

0.33pd

what is the pd tolerance for unwanted vertical prism?

1.0mm

what is the mm tolerance for unwanted vertical prism?

2.5mm

what is the mm tolerance for unwanted horizontal prism?

0.67pd

what is the pd tolerance for unwanted horizontal prism?

distance reference point

where distance power is measured through on PAL, prism is not valid here

fitting cross

optically nothing for a PAL, only used for getting the lens positioned correctly on a PAL

prism reference point (major reference point)

where monocular PD location is verified optically; horizontal & vertical prism are verified here on a PAL

near reference point

where add power is verified on a PAL

DRP

A

hidden add power engraving

B

fitting cross

C

NRP

D

manufacturer’s hidden identifying logo

E

shapes used to locate the fitting cross & NRP

F

PRP or MRP

G