Pantoscopic tilt maybe?

[bta89]

I've got a patient with an RX: -4.75, -2.00, 010 OD and -4.75, -2.75, 160 OS with a pd of of 61. She got a pair of sunglasses (Trivex with an 8BC ) and it didn't work out. She said when she tilts the frame lower on her ear and there isn't as much tilt it works out a lot better. I was wondering if there is possibly too much pantoscopic tilt in the frame. If this is the case, do I need some sort of tool to measure for that? If so where would I be able to get one? Also is youtube the best place to try and learn how to measure for it? I don't know how to measure for it so I need to learn how too.

[uncut]

bta89:
I would check to see where the vertical O.C. is actually located. If low it could create a perception of discomfort. Additionally, and perhaps more importantly, measure and record vertex distance, with both positions. Compare this with the vertex of the clear, daily worn eyewear if current. A increase in vertex distance can also affect the visual outcome.

By tilting the eyewear toward the eye, (and possibly upward) the effective power of the lens is increasing, and the 8 base is compensated for peripherally.

[Chris Ryser]

Please let us know what the base curve is on customers clear daily glasses.

Most probably one could assume that it is a base curve of +2.00 which would make a difference perception of image.

[brandonlef]

8 BC on its own may create some distortion. The lifting of the frame would however indicate that an accurate OC needs to be taken. Did you do this? Vertext distance may help as most lens manufacturers will compensate their lenses with how close or far away the frame sits on the face. As for the the panto tool..try mccray? I'm not sure whoelse makes them. We have them and use them alot for progressives as our main lens manufacturer for progressives takes this measurement into account.

[bta89]

Thanks for the help. She will be coming in in a few days from now. I will be sure to measure her BC in her everyday pair and compare the two. I will measure for the vertex distance in both pair and see what I can come up with.

[cowboytelemark]

I probably wouldn't fit that patient in an 8 base at all. Too much cyl. She probably prefers the reduced vertex distance because this makes it harder to notice the peripheral distortion. The reduced panto is probably not what she is liking, it is the reduced vertex. As others said, OC height is important (which unfortunately will likely make her lower margin thicker). If you do leave the patient in this frame I would DEFINITELY make sure the lab is doing a compensated Rx to account for the wrap. If it were me I would cut my losses and do a frame change to a flatter base curve.

[Robert Martellaro]

http://www.opticampus.com/files/memo...on_of_wear.pdf

http://www.optiboard.com/forums/atta...7&d=1158870494

Your lab might be able to set you up with some type of plumb-line device for measuring the pantoscopic tilt. You'll also need a distometer to measure the wearer's vertex distance. The lens needs to be made by a lab that has a free-form generator and software that is first-rate for compensating for position of wear.

Because of the Rx, I would prefer a +6 BC lens, increasing the wrap angle to look and function more like a +8 base wrap sunglass. But even with a +6 BC, the lens will still be somewhat thick and heavy, especially with -7 D in the horizontal meridian. For these types of RXs, that is more than -4.00 D, consider traditional sunglass frames, or possibly an Rx insert.

[drk]

If I may, you probably forgot to compensate for wrap.