Help with PALs that move

[Neophyte Optician]

Patient with new PALs - varilux comfort enhanced with a seg height of 15.5 OU. She says that when she moves her head from side to side while looking at a distance that everything below her line of sight seems to be moving or wiggling but that everything at a distance is stationary. She also says that when she is looking downward at near that everything appears to be moving and wiggling. Her Rx compared to her old PALs has not changed. The front BC of her new PALs is different than her old PALs. Her new frame is much smaller than her old ones. The fitting cross matches her PD, but is 1mm lower than where she is looking through. What is causing her complaints, and what can I do to address her concerns?

Thanks for the help.

[uncut]

First,

I would check the pantoscopic angle difference between the two sets, and perhaps, assuming the new BC is steeper than the previous pair, increase the pantoscopic angle.

[Jubilee]

As uncut specified, I would check the panto first and adjust..

However, I wonder if part of the issue is that she is now in the "short" corridor version. So less intermediate, getting into the reading/near sooner..

[Neophyte Optician]

This patient's frame has a large thick temple, so increasing panto may be difficult. Any suggestions?

As uncut specified, I would check the panto first and adjust..

However, I wonder if part of the issue is that she is now in the "short" corridor version. So less intermediate, getting into the reading/near sooner..

[Robert Martellaro]

This patient's frame has a large thick temple, so increasing panto may be difficult. Any suggestions?

I suspect that the second part of Jubilee's response explains most of your client's symptoms. I believe the Enhanced Comfort varies the corridor length depending on the fitting height and frame shape, the latter for any upsweep at the near fitting point. Because the frame selection is more or less written in stone, I'd tell your client that due to the above factors, they should allow about ten days for adaptation.

I should mention that I could not (comfortably) wear a PAL at 15.5mm high, primarily due the narrow vertical lens size, and also due to the proximity of the bottommost part of the frame to my near field of vision, even with a close 12mm wearer's vertex distance and generous pantoscopic tilt. I prefer about 19mm high, or more, for this 2.25 add avid reader, although you might have more latitude with lower add powers, and for those with infrequent close tasks.

[Neophyte Optician]

Thanks for the help. I'll relay that to the patient - I hope they understand.

On a related, why wouldn't having a shorter B as opposed to a longer B make it easier for a client to use their PAL? My thought, though obviously in error, is that the client would then not have to try to move their eyes as far down in order to get the maximum add. Would you please explain to me the thought behind better reading with longer seg heights (I'm trying to learn).

Thanks!

[Robert Martellaro]

Thanks for the help. I'll relay that to the patient - I hope they understand.

On a related, why wouldn't having a shorter B as opposed to a longer B make it easier for a client to use their PAL? My thought, though obviously in error, is that the client would then not have to try to move their eyes as far down in order to get the maximum add. Would you please explain to me the thought behind better reading with longer seg heights (I'm trying to learn).

Thanks!

Here's an example. I just placed a frame with a 24mm B in front of my eyes. The bottommost part of a magazine is below the lens, forcing me to lower my chin significantly (a grevious error if they're an avid reader). To see the top of the page, I have to raise my chin significantly. When I look at the page about two thirds of the way down, I'm essentially looking through the bottom edge of the lens (avid readers will be miserable). A short corridor lens will reduce the chin lift needed for the top of page, but as usual, there are consequences, primarily with increased distance peripheral blur, and a busier, more dynamic feeling lens.

Looking at the same magazine with my every day eyeglasses (32mm B), I can see to the bottom of the page without posturing, with the bottom edge of the lens well below the bottommost part of the page. To see the top of the page I have to lift my chin slightly. However, too long of the corridor, in some Rxs, will require more posturing when looking at the top of the page, aand even near the bottom of the page, if the print is very small or the lighting is poor.

BTW, my every day lenses are Auto II fixed 18's, which I would describe as a medium corridor PAL. Moderate myope, astigmatism, and +2.25 add.

You'll have more latitude with lower add powers/emerging presbyopes, but we need give this a lot more consideration when the add power is above about +1.75.

Learn more by reading...

http://www.opticampus.com/cecourse.p...essive_lenses/

Scroll down to "The Progressive Corridor"

Hope this helps,

[uncut]

Thanks for the help. I'll relay that to the patient - I hope they understand.

On a related, why wouldn't having a shorter B as opposed to a longer B make it easier for a client to use their PAL? My thought, though obviously in error, is that the client would then not have to try to move their eyes as far down in order to get the maximum add. Would you please explain to me the thought behind better reading with longer seg heights (I'm trying to learn).

Thanks!

Your logic makes sense, but in everyday life, the power(s) used are many, and not just the add.

Robert has covered it beautifully, in the above post.

In order to cram more powers into a limited space(short corridor), some powers(radius) are given very little space.

Think of a topographical map, interpreted into landscaping a neighborhood of back yards, all with the same elevation, and lot length, but with different methods of gradation, terracing, etc. and all with different patio sizes at the bottom elevation. A terrace would be a lined bifocal!

[uncut]

This patient's frame has a large thick temple, so increasing panto may be difficult. Any suggestions?

It it rare to find an ophthalmic frame that can't have some panto change. Careful filing of a wide arm, after panto hinge change can be accomplished. Remove temples before filing.

Look at the temple ends, starting at the area about 10 mm in front of the ear, can a slight angle down be accomplished, there? Can the temple be arched?

[Uncle Fester]

Feel free to steal my "new pair of shoes syndrome" razzle dazzle when this problem crops up again- as it inevitably will.

I'll tell this patient in a relaxed manner that the new glasses often need some time to adjust too. I tell them there's a new rx and "new window" that they're now looking through. Then I tell them that "nothing fits like an old pair of shoes (which most of us instantly relate too) and that "since you've been wearing the old pair for years an adaptation period is expected. Try not to dwell on it and as time goes by you'll find the eye and brain get used to the new image and the swim will become less and less noticeable but for now the eye is being sensitive to any changes and the unconscious is asking the conscious to recognize the swim. It's a lot like when you get a new frame and see the edges of the frame for a while and then it goes away" (another thing most people can relate too).

Hope it helps-

[EyeCare Rich]

Nice method Fester. I like it! This is especially true when an Add power has increased by any amount. I takes some time. The more you as an optician come across this issue, the more comfortable you get in helping the patient understand in simple terms. Good luck Neophyte!