SV Plus Rx OC Question

[NCspecs]

I have a patient who has been fitted in a traditionally surfaced poly, OD +2.25/ OS+1.75, -0.25 cyl ou.

I know that many digitally surfaced lenses suggest that when taking an OC for a plus Rx you want to drop it 4 mm to accommodate for the pantoscopic tilt of the frame. I take OCs for all of my SV jobs but I have left OCs where I dot them. Should I be doing things differently for my hyperopes? I think that if I left her OC at 30 (big ole hipster frame) she might be okay because she barely has any cyl to speak of, but I obviously have room to drop it if I need to.

What say you?

[Robert Martellaro]

I have a patient who has been fitted in a traditionally surfaced poly, OD +2.25/ OS+1.75, -0.25 cyl ou.

I know that many digitally surfaced lenses suggest that when taking an OC for a plus Rx you want to drop it 4 mm to accommodate for the pantoscopic tilt of the frame. I take OCs for all of my SV jobs but I have left OCs where I dot them. Should I be doing things differently for my hyperopes? I think that if I left her OC at 30 (big ole hipster frame) she might be okay because she barely has any cyl to speak of, but I obviously have room to drop it if I need to.

What say you?

The 180 line might bisect the pupil, the Autograph for instance, or it might be 6mm below, Zeiss for instance. Provide a fitting height that is equal to the pupil position in the primary gaze.

Both of the above lenses are optimized for POW. If you are using non-optimized lenses, follow the manufactuer's instructions.

The above is true for all types of refractive error, except when there is prescribed vertical prism.

[Barry Santini]

Please:

You are not taking an OC height in SV, FF or not. You are ALWAYS taking a pupil height.

Period.

B

[NCspecs]

The 180 line might bisect the pupil, the Autograph for instance, or it might be 6mm below, Zeiss for instance. Provide a fitting height that is equal to the pupil position in the primary gaze.

Both of the above lenses are optimized for POW. If you are using non-optimized lenses, follow the manufactuer's instructions.

The above is true for all types of refractive error, except when there is prescribed vertical prism.

Thank for for your succinct response Robert.

[nicksims]

Barry,
I was wondering how long before you jumped in here. You did not let me down!

[Robert Martellaro]

Thank for for your succinct response Robert.

Sorry. Busy day. I figured that a short answer would be better than no answer. If you want to dig deeper, I'm all ears.

Please:

You are not taking an OC height in SV, FF or not. You are ALWAYS taking a pupil height.

Period.

B

I still call it an OC height when fitting by Martin's rule for tilt, or for finished/semi-finished aspherics. But when the design calls for a pupil position, I'm comfortable calling it a pupil height, fitting height, or fitting point.

[NCspecs]

Sorry. Busy day. I figured that a short answer would be better than no answer. If you want to dig deeper, I'm all ears.

No, no, I really meant it. Your response was incredibly useful. That's exactly what I was looking for, to the point and the reasoning behind it. You are the best! Merry Christmas.

[Robert Martellaro]

Thanks for the kind words.

It sure is hard to get this information from the manufacturers; the labs rarely have personnel capable of providing the "science", and/or the right answers.

For example, I just got off the phone with an optician at "technical" for a big lens manufacturer who makes a POW, and non POW optimized single vision lenses. The question was, where to place the design pole with the non-pow design when there is significant power and tilt.

The answer I got was vague- go ahead and use Martin's rule for tilt. But when I pushed back, I was told that yes, the design was meant to be aligned with the pupil in the primary gaze. My conclusion was that it should not be used with high tilt values combined with moderate to high powers. The optician seemed somewhat irritated that I gave a damn.

It's frustrating that the lens manufacturers generally don't discuss in detail how to fit their lenses. There should be plenty of technical discussion on their web sights! But most of what I see is marketing. Even the some of the white papers are gibberish. I hate to name names, but has anyone read the "S" white paper? WTF.

Okay, I'll return now to don't worry be happy mode, and best wishes to all.