Looking for a solution

**Bev Heishman** · 10-15-2004, 01:58 PM

Hey all,

I have an Rx that has been very challenging for my wholesale lab. Today the lab manager called me and said that he gives up in trying to surface the lens.

At present I have an rx that calls for a "total of 6 prism diopters base down & out equivalent at 15 degrees. This can be accomplished with 3base down and out at 15 degree in the right lens and 3 base up & out on the left eye.

Patient has been wearing a Fresnel Prism for quite some time. The rest of the details are:

Rx OD +3.00-.50 x 103 ADD +1.75 PD 70 DPD 67 NPD
OS +2.50-.50 x 083 ADD +1.75 CR39 FT-28 19 high

Wearing Seiko T573 59-16

Believe the total resultant prism is for approx 5.8 out and 1.5 DN at 15 degrees. Correcting for Esotropia/Right Hypertropia.

Any thoughts? Of course thepatient thinks this job should have taken less than a week. (of course!)

BEV

**shanbaum** · 10-15-2004, 02:12 PM

I don't see why this Rx should be so difficult. Did your lab say in exactly what way the result they were getting was unacceptable?

**Bev Heishman** · 10-15-2004, 02:32 PM

Hi Shanbaum,

I was told that the prism is not coming up in the correct position. I just called and asked if they have sent this out to Epic.

**shanbaum** · 10-15-2004, 02:52 PM

It just doesn't look all that remarkable.

They probably ought to enter the prism in its polar form: 3D at 195 on the right and 3D at 15 on the left.

**Joann Raytar** · 10-15-2004, 05:47 PM

Robert,

Some of our prism jobs come out odd if the lab still applies prism thinning. Could this be a culprit?

**karen** · 10-15-2004, 07:43 PM

Bev, we are really good at this kind of stuff. I sent an email to my lab manager to see if they have any suggestions...I'll let you know what they say.

**PAkev** · 10-15-2004, 08:43 PM

Hi Bev,

Is it perhaps the larger eyesize that compounds the problem ? My guess is they can not get enough sag out of the blank to come up with the prism while also enabling the lens to cut out. It's been quite a while since I've surfaced leses but I recall this being a problem from time to time.

As per the PD, I guess this is a larger guy but perhaps a brief explanation of the problem will enable him to consider a smaller frame.

Kevin

**shanbaum** · 10-16-2004, 08:06 AM

Originally Posted by Jo

Robert,

Some of our prism jobs come out odd if the lab still applies prism thinning. Could this be a culprit?

Our software doesn't automatically prism thin when there's a vertical component to the Rx prism. Not because it would come out odd, particularly, but because it would be harder to measure.

**Darryl Meister** · 10-16-2004, 05:12 PM

Just a couple of comments...

This prism prescription is very ambiguous. You cannot have a "total" amount of prism at a particular axis, without having one eye as a reference point, since the horizontal prism components would cancel between the two eyes using the same axis. You can have 6 PD @ 15 in either the right or left eye, but not both if you plan to correct for a muscle imbalance.

As Robert stated, you can convert this into polar form for less ambiguity. However, the most practical and least confusing approach would be to convert this completely into rectangular form (in/out, up/down) with no axis specification. Many progressive lenses will have some residual prism at the prism reference point even without prism-thinning. Knowing what the rectangular prisms are would simplify the verification process in this case.

Best regards,
Darryl

**Bev Heishman** · 10-18-2004, 08:28 AM

Darryl,

I had asked the lab to change this Rx over to place the full prism correction in the OD. Still can't do. Extra thick blanks were used multiple times with no success.

Of course what is giving the largest problem is that this individual developed this third nerve palsy 2 months after receiving his glasses. The Fresnel was used to as temporary measure. Unfortunately, this palsy did not fully resolve.

I agree with Kevin also that we need to bring the frame size down. The individual does not want to spend the money. If not the Fresnel will be the permanent solution.

Thanks for your thoughts!

**Darryl Meister** · 10-18-2004, 07:18 PM

What problems with the job has the lab been having? Can they tell you what their prism readings have been?

Best regards,
Darryl

**karen** · 10-18-2004, 10:06 PM

Bev, sent a copy of your original messsage to the lab and it seemed pretty run of the mill ( as prism jobs to) to them. If you are still having problems I can put you in touch with someone there that can at least answer some of your questions.

**Bev Heishman** · 10-20-2004, 06:10 PM

My optom and I reviewed Darryl's and Shanbaums info. We also decided to pprove it in the lensometer using trial lenses. We re configured and ordered appropriaterly. Extra thick blanks are on order.