Seg Height Measurement

[j_platinumplus]

Okay, I keep getting two different answers on this question:

When measuring a seg height do you measure to the bottom of the lens and add .5mm, or do you measure to the bottom of the frame?

Thanks in advance!

[Jacqui]

In the lab we measure to the bottom of the lens.

[j_platinumplus]

Do you add the .5 mm to make up for the groove or not?
Thanks!

[Pete Hanlin]

I usually measured to the bottom of the lens and added half of the frame thickness. So, if you have a chunky zyl frame, you might end up adding 1mm. If you have a metal frame, it usually works out to 0.5mm.

[Jacqui]

In wholesale work I was always taught the bottom of the lens, period. My customers may be calculating this before I get the Rx.

[mullo]

I usually measured to the bottom of the lens and added half of the frame thickness. So, if you have a chunky zyl frame, you might end up adding 1mm. If you have a metal frame, it usually works out to 0.5mm.

Same here.

[Clive Noble]

I don't think it matters which way you take the measurement as long as the person edging and fitting the lens knows how you measured it.

[Lewy]

I find it better to measure the height above or below the datum line. Flat tops in general lie 2mm below the datum and PAL's tend to sit at about 4mm. See previous post in the Prog lens forum for technique.


Lewy