Troubleshooting Scenario

[Hayde]

Patient with Rx:

-4.50 -0.50 180ish
-4.50 -0.50 180ish
Add: +2.00

orders two pair of progressive specs: one clear, one polarized. Both with AR; (shades with backside only.) 1.60 on the clear; poly on the shades.

patient's previous pair of clear progressives identical in brand and material, same line of AR. Old correction virtually identical to new pair save the add power has jumped from +1.25.

Patient experiences disatisfactory focus and swim in clear pair; no complaints in shades.

***

Doublechecked script and measurements. Old and new clear specs share base curve, comporable vertex, fitting height, and pd.

Can discern no difference between the new pairs under the lensometer. No apparant warpage or waves.

The jump in add power seems a red herring given her immediate and stark preference for the polarized pair.

I would think wrap could be a factor, except her old clear pair is as flat as her news clear ones.

Tested her vision between both new pair on a reading card at 60 cm out:


Clearest range: OD OS OU
Clear: 17cm(12/5) 21cm+(0/21+) 34cm+(12/22+)
Shades: 23cm(12/11) 25cm+(3/22+) 34cm+(12/22+)
[+denotes border of reading card--outer limit of clearest zone not determined]

Patient reports that the 'clear zone' of the clear pair didn't compare to the clarity in the shades.

***

My working induction is that there's distortion in the clear pair that I haven't detected yet.

What are your thoughts on isolating the cause of her symptoms?

Investigative method from here?

Something else I've missed?

Thanks for chewing on my mystery with me.

[edit: corrected units to cm]

[opty4062]

Is the B size very different from the older clear pair to the new one?

[Hayde]

B is virtually identical from old clear pair to new--same seg height.

[Trip]

My first thought is that there is a difference in the monocular PD's between the clear / suns ..... and or the lens(es) are bit tilted/twisted from edging or mounting.

Second .. is there any chance that suns are under powered relative to the clear? Something is driving the perceived difference between the two ...

[Jubilee]

You mention that the clear pair has the same PAL design and material as prior. What about the sun? As the add changes, the design experiences some changes too. Perhaps she is detecting those changes (more unwanted cyl/blur..more narrow corridor)

[m0002a]

Patient with Rx:

-4.50 -0.50 180ish
-4.50 -0.50 180ish
Add: +2.00

orders two pair of progressive specs: one clear, one polarized. Both with AR; (shades with backside only.) 1.60 on the clear; poly on the shades.

patient's previous pair of clear progressives identical in brand and material, same line of AR. Old correction virtually identical to new pair save the add power has jumped from +1.25.

Patient experiences disatisfactory focus and swim in clear pair; no complaints in shades.

***

Doublechecked script and measurements. Old and new clear specs share base curve, comporable vertex, fitting height, and pd.

Can discern no difference between the new pairs under the lensometer. No apparant warpage or waves.

The jump in add power seems a red herring given her immediate and stark preference for the polarized pair.

I would think wrap could be a factor, except her old clear pair is as flat as her news clear ones.

Tested her vision between both new pair on a reading card at 60 cm out:


Clearest range: OD OS OU
Clear: 17cm(12/5) 21cm+(0/21+) 34cm+(12/22+)
Shades: 23cm(12/11) 25cm+(3/22+) 34cm+(12/22+)
[+denotes border of reading card--outer limit of clearest zone not determined]

Patient reports that the 'clear zone' of the clear pair didn't compare to the clarity in the shades.

***

My working induction is that there's distortion in the clear pair that I haven't detected yet.

What are your thoughts on isolating the cause of her symptoms?

Investigative method from here?

Something else I've missed?

Thanks for chewing on my mystery with me.

[edit: corrected units to cm]

Maybe I missed this, but are both new lenses the same brand and design (I know they are different materials). Is there some reason why the brand/design is not disclosed?

The only thing I can think of if the lenses are the same is chromatic aberration, since in theory, I would think that a clear lens that allows the full spectrum of light should be more susceptible to chromatic aberration than a tinted one, but not sure how a polarized lens factors into this. On the other hand, 1.60 has less chromatic aberration than poly. However, I wonder exactly which 1.60 was used since MR-6 only has a an abbe value of 36 (compared to 41/42 for MR-8/MR-20).

[braheem24]

Top 3 for me...

1. Lens design variance.
2. BC
3. Vertex

[drk]

Low hanging fruit is position of wear.

[Jason H]

Did you intentionally measure the sunglasses low?

[Hayde]

Thanks for your interest and good questions, everyone.

I've never differentiated segs for polarized versus shades; have already verified all segs for all three pair are sitting identically.

The progressive is a VPE (Varilux Physio Enhanced) for all three pairs. Bumping to a VPE fit seems like an option to factor in vertex, wrap, and tilt--or even an S Fit, except for the fact her old frames are so uncannily similar in dimensions and fit to the new ones.

The shades being underpowered is an excellent avenue to rule out...could explain some of the differential reaction from the patient. Polarized progressives are a real pain to dot up and inspect...but alas I did.

Tough one, isn't it?

On the other hand, 1.60 has less chromatic aberration than poly. However, I wonder exactly which 1.60 was used since MR-6 only has a an abbe value of 36 (compared to 41/42 for MR-8/MR-20).

Nice one! I'll check on that. Not really expecting any 1.60 HI to underperform poly on Abbe, but maybe the frame wrap on the shades or cylinder axes cancels out more than excacerbates? (exposing my ignorance here.)

Thanks for the all the thoughts, y'all. It's appreciated.

[Robert Martellaro]

Patient with Rx:

-4.50 -0.50 180ish
-4.50 -0.50 180ish
Add: +2.00

Old correction virtually identical to new pair save the add power has jumped from +1.25.

Patient experiences disatisfactory focus and swim in clear pair; no complaints in shades.

Doublechecked script and measurements. Old and new clear specs share base curve, comporable vertex, fitting height, and pd.

You mention that the clear pair has the same PAL design and material as prior. What about the sun? As the add changes, the design experiences some changes too. Perhaps she is detecting those changes (more unwanted cyl/blur..more narrow corridor)

That's where I would look.

For example, the clear PAL might be a less refined design, maybe with a more aggressive power profile in the corridor that was satisfactory in the low add power, but falls apart when the add ramps up. The client might have been able to adapt, but they have the sun Rx as a means of comparison. They are bewildered as to why there's such a difference in performance between the two pairs of eyeglasses with the same Rx (of course, as opticians, we know that is quite common!). The answer may be that the sun PAL may have a longer corridor that feels and performs better than the clear PAL, at this add power and distance Rx.

The solution may be as simple as using a similar design in both pairs. However, it's possible that they will experience better results if the PAL designs are different in each pair. After all, they are used in entirely different circumstances: suns typical need the best distance performance, clears more of a balanced performance depending on the Rx and their visual needs. The key is to inform the client beforehand, so that there will be no surprises.

[Robert Martellaro]

The Physio enhanced has a variable corridor length. The clear may have a shorter 'true' fitting height (including the shape) than the sun pair.

[mshimp]

Polarized lens perhaps is diminishing the magnification increase in the reading portion. Just throwing that out there. I have noticed patients don't have any problems with abbe effect with poly polarized lens. I know this is not an abbe related issue. Dittos to what braheem 24 said as well.

[ak47]

+1

That's where I would look.

For example, the clear PAL might be a less refined design, maybe with a more aggressive power profile in the corridor that was satisfactory in the low add power, but falls apart when the add ramps up. The client might have been able to adapt, but they have the sun Rx as a means of comparison. They are bewildered as to why there's such a difference in performance between the two pairs of eyeglasses with the same Rx (of course, as opticians, we know that is quite common!). The answer may be that the sun PAL may have a longer corridor that feels and performs better than the clear PAL, at this add power and distance Rx.

The solution may be as simple as using a similar design in both pairs. However, it's possible that they will experience better results if the PAL designs are different in each pair. After all, they are used in entirely different circumstances: suns typical need the best distance performance, clears more of a balanced performance depending on the Rx and their visual needs. The key is to inform the client beforehand, so that there will be no surprises.

[ak47]

+1

The Physio enhanced has a variable corridor length. The clear may have a shorter 'true' fitting height (including the shape) than the sun pair.