reticle circle dispute at work, .50D circle, or 0D?

**LastVisibleCanary** · 03-06-2010, 01:14 AM

We have a Bausch & Lomb model 70 vertometer at our lab and we've had some issues with jobs being late because I'll send them back to be refined to get the prism to come in better. My understanding was that the first circle represented .50D of prism, the center of the first circle being 0. I'm now being told that the first circle (thin) represents 0.0D and the second circle (thick) is 1.0D, third circle (thin) 1.5D, and fourth circle (thick) 2.0D.

This is coming from the optometrist, so I have to question whether I was trained correctly or not. it seems insane to me that a lensometer manufacturer would make a thin-thick-thin-thick ring set up be anything but 0.5, 1.0, 1.5, 2.0.

Can anyone here point me in the dircetion of a printable example showing what the first ring represents? I've been told something different by my lab manager, store manager, and optometrist, and as a lab tech I don't really have any say in the matter unless I can provide something concrete.

**braheem24** · 03-06-2010, 07:18 AM

It's 0.5 prism, 0 does not have a circle otherwise one side of the 0 would be BI, the other BO, BU, BD.

**LastVisibleCanary** · 03-06-2010, 10:09 AM

Originally Posted by braheem24

It's 0.5 prism, 0 does not have a circle otherwise one side of the 0 would be BI, the other BO, BU, BD.

I managed to find 3 lensometer manufacturer spec sheets qouting the first line as .5, so hopefully that will be enough to convince them that .5 up +.5 down = 1.0 diopters of up/down prism.

**braheem24** · 03-06-2010, 10:22 AM

Put a 0.5 prism from the trial lens set in the lensometer and show him where it focuses.

**LastVisibleCanary** · 03-06-2010, 07:51 PM

If we have a trial lens set, I'm not sure where they are. I ended up taking a -1.00 finished lens and had her dot it up at the top of the first ring, then at the bottom of it. using prentice rule, 10mm of seperation on a -1.00D lens = 1.0D of prism, thus it's 0.5D+0.5D of prism. To do a secondary verification we have a reichert digital that shows both center mark up dots being .5 up and .5 down. If there's any further question about it I'll have her do the same thing with marking it up 1/2 way between center and the first ring to show that it's .25D of prism.