Computer progressive manipulation

[DanLiv]

I would like to know what solution you all use for this case, see if someone has a bright idea I've overlooked.

Need computer/near glasses (to wear over CLs, but I think that's immaterial). For very low adds I use Eyezen, higher typically Shamir Computer/Workspace. In this case the doc has figured the exact computer and near powers he wants:

OD +0.25 sph add +1.25
OS +0.25 sph add +1.25

Eyezen won't give me enough add, but to get the computer lens to have the +0.25 at the MRP while only a +1.50 total near power I would have to fudge the Rx I give the lab. The Shamir Computer gives ~50% of the add power at the fitting height, so I calculate to get the powers I want where I want I would need to supply the lab an Rx of -1.00 sph add +2.50 (half the add would be +1.25, combined with the -1.00 would get me my +0.25).

I think this would work, my only concern is the artificial power delta I'm creating and how much distortion it will induce. The delta on paper is a huge 3.5D which would be rough in a progressive, but am I correct in thinking in the computer the delta be less since the -1.00 is never realized? The add keeps digressing above the MRP, but probably only another -0.50D at most (in this particular fit there is only 11mm from the MRP to the top of the lens). Therefore the actual delta in the lens would only be the desired 1.25D from MRP to near, and a max 1.75D from top of the lens to bottom. Am I correct?

I really shouldn't have to abuse the lens design and manipulate the submitted Rx like this to get what I want. Is there another lens solution some of you use in this case? Why can't the designers make a computer lens that let's me specify the intermediate and near powers like I would with a progressive?

P.S. I know a straight top would solve all of my woes. I'm looking for a no-line solution.

[Robert Martellaro]

The delta on paper is a huge 3.5D which would be rough in a progressive, but am I correct in thinking in the computer the delta be less since the -1.00 is never realized?

The power "delta" is only 2.5D (-1.00/+1.50), less if as you stated the Shamir Computer doesn't try to produce the full distance Rx.

Why can't the designers make a computer lens that let's me specify the intermediate and near powers like I would with a progressive?

They're thinking what people who aren't thinking, are thinking. In other words, many of us are going to be replaced by non-thinking machines.

Until that happens, use a PAL or segmented with +.25 distance add +1.25 if the monitor is about 30", a +.50 distance add +1.00 if somewhat closer, and a +.75 distance add +.75 if significantly closer. Tweak with flippers or by trial framing. Make sure the client has measured the work distance(s).

Hope this helps,

Robert Martellaro

[Hayde]

Hi Danliv. May I ask how you calculated the 3.5D? [edit: Robert beat me to it!]

[drk]

I think Robert's right, again.

When prescribing for computer workstations, we can do one of two things:

1. Use a pre-fab design, like Shamir's stuff, etc. They make the decisions ahead of time. You provide the presbyopia level.

2. Use a custom design. That's what the prescriber in this case apparently expects. But when you do a custom design, as you're finding, there aren't as many lenses that allow customization.

I go el-basico sometimes, with the SolaMax if cheapness counts, or a better PAL if I have to. But the add progression even on a full presbyope is like, +1.25 or so, and that doesn't require particular sophistication (unless there's a lot of stigmatism or sumpthin.)

[DanLiv]

Yeah I'm going to end up just going progressive, I'm afraid what futzing so much with the computer design will do.

Thanks for the power delta correction!