Dealing with phorias and tropias

[Wes]

Someone posed the following question to me, and I will reiterate to the rest of you.

"I had a question for you that my OD presented to me. The doc specializes in neuro-optometry with a concentration on vision therapy so we see alot of brain injuries, eso/exo phorias, amblys and the like. The question he posed was the use of PALs on an exo/eso patient and moving the PD to accommodate those eye turns. Is it acceptable to move PD's out for and exo and vice-versa so the patient isn't automatically looking into the peripheral blur area? I told him I have never heard of that being done but I was determined to find out. My first thought was to ask the optical gurus here on OB! Whatever thought you have on this subject would be greatly appreciated!
Thanks for your time!"

My reply:
"Hmm, here's my take on that. It depends on a lot of things, and some experimentation may be needed.
With phorias, I measure each eye individually, straight on, and use the pd I get from that. Tropias can be more problematic, as the deviation is there full time, unlike with a phoria. In my experience, someone with an eso/exo-tropia will tend to use one eye at a time, sometimes using one for near and one for far depending on strength of rx in each eye, but primarily using whichever is dominant. The use of prisms may or may not assist with fusion, and this often depends on how long the person has had the issue, and how long they have been adapted to it. These are things that the doc and you will need to discuss with the patient. With all of that said, I usually end up following the same procedure as with a phoric eye, and the patient is left using one eye or the other. This may not sound ideal, but sometimes trying to force fusion on a patient that has had a tropia for years doesn't work, and also, many people cannot deal with two distinct, yet clear images and often they have trained themselves to accept only one at a time, and so the blur associated with looking into the periphery of a PAL is welcome. Surgery may also be an option. The desires of the patient and his/her willingness to try options are key here. With amblyopia, where the patient's brain has basically "turned off" the eye, there's not much to be done. Perhaps a nice balance lens? "

Suggestions? What do you do?

[chip anderson]

I will as usual hear a lot of dissent on this but: When I have a subnormal vision problem of any type or a strabismus problem, I won't use a PAL under any circumstances. As to measuring a PD the blocking the fellow eye and measuring the gaze at the center of fixation of the eye being measured is the correct proceedure.
If the patient can't see well to begin with why use a lens that will probably exaserbate the situation?


Chip

[RIMLESS]

I definitely agree with Chip. 95% of the time a PAL will only make a bad situation like what was described much worse.

[Jacqui]

I will as usual hear a lot of dissent on this but: When I have a subnormal vision problem of any type or a strabismus problem, I won't use a PAL under any circumstances. As to measuring a PD the blocking the fellow eye and measuring the gaze at the center of fixation of the eye being measured is the correct proceedure.
If the patient can't see well to begin with why use a lens that will probably exaserbate the situation?


Chip

+1

[braheem24]

... And when the patient comes in happy with their PALs wanting a new rx, should Wes stick his head in the sand?

[MakeOptics]

The Zeiss Individual allows you to play with inset, I have also in the past used PALs and rotated them a few degrees and had the Rx surfaced to compensate for the rotation. (before anyone says it can't be done that's how inset used to be done). I am always willing to give it a try if the patient is eager, willing, and cash pay.

[MakeOptics]

I don't mean to offend with this statement but I have found that older opticians tend to shy away from newer technology and from trying new things, the tendedncy seems to be to go to the comfort zone and fit what's safe. In my experience I have seen things not work out 4 out of 10 times but the 6 times they have worked I have a client for life, the other 4 were willing to give anythign a try and were still satisfied when we went safe.

[RIMLESS]

I don't mean to offend with this statement but I have found that older opticians tend to shy away from newer technology and from trying new things, the tendedncy seems to be to go to the comfort zone and fit what's safe. In my experience I have seen things not work out 4 out of 10 times but the 6 times they have worked I have a client for life, the other 4 were willing to give anythign a try and were still satisfied when we went safe.

That's a broad generalization. It's not that they tend to shy away from newer technology, it's more like the older opticians typically have more experience under their belts. They know when to properly utilize the newer stuff but more importantly when not to.

[Robert Martellaro]

Someone posed the following question to me, and I will reiterate to the rest of you.

"I had a question for you that my OD presented to me. The doc specializes in neuro-optometry with a concentration on vision therapy so we see alot of brain injuries, eso/exo phorias, amblys and the like. The question he posed was the use of PALs on an exo/eso patient and moving the PD to accommodate those eye turns. Is it acceptable to move PD's out for and exo and vice-versa so the patient isn't automatically looking into the peripheral blur area? I told him I have never heard of that being done but I was determined to find out. My first thought was to ask the optical gurus here on OB! Whatever thought you have on this subject would be greatly appreciated!
Thanks for your time!"

The central vision is suppressed when the eye is in the deviant position, so I position the lens according to the monocular/occluded PDs.

I have more than a few heterotropic clients- quite a few of those are wearing PALs fit by me, even though I fall in the old-timer category!

[pseudonym]

I posted about a similar situation recently which was complicated by a remake due to Rx change. Elderly lady, history of stroke, diabetes, and a tropia. She insisted on a PAL, which she said had worked for her in the past. Her old glasses had the pd several mm off from our occluded pd reading.

This is where I really learned something: The boss made the call to split the pd difference.

The lady stops in regularly to let us know how much she loves her new PALs.

[braheem24]

Where's DRK? This is all up his ally/lane.

[SharonB]

My own personal experience went thusly: I have a phoria (OS - exo) that is pretty much in control during the day, but as the hours wear on ( or I have a couple of glasses of wine) that eye swings out. From childhood I somehow learned to suppress the OS to avoid diplopia when it happened. When it was time for PALs, and with years of optical experience under my belt, I messed everything up by using PD measurements that were in the phoria position. Somehow that made good optical sense to me at the time. I had a colleague take them with the pupilometer not occluded. Why? I guess I over-intellectualized the whole thing. Big time mistake!!!! For the last 20+ years I have used monocular occluded measurements taken in the orthophoric position.I wear my PALs with no problem. I may still suppress (how can you erase a visual pattern learned from childhood?), but it works for me. I've used that procedure for all of my phoria patients. Now...the tropias - I find that Pseudonym's solution usually works.

Unrelated P.S. Phorias are fun! When you can easily suppress one eye, all of our ophthalmic instrumentation can be used with both eyes open, and it's great for playing darts, and dropping clothes pins into milk bottles (anyone remember that birthday party game? Or, milk bottles?

[drk]

Thanks, Braheem.

I think everyone is right: Wes, Robert, Susan. It's actually a no-brainer, fortunately.

In a phoria, the eyes are fused all the time, it's just that they strain to hold together. So, no compensation for eye misrotation needed. Measure p.d.'s as always: monocular, occluded.

In a tropia, by definition, the eyes are unfused at least part of the time. But they'd see double if they didn't suppress their vision. If they're suppressing, then they can't see any blur. If they're not suppressing, the double vision problem far outweighs blur from looking through the wrong part of the lens.

To measure p.d. for a tropia, same standard method: monocular, occluded p.d.s. Maybe the deviating eye will always turn so the p.d wouldn't matter, but maybe sometimes it will fuse and it will need the correct p.d. Maybe one eye deviates sometimes, and then the other.

Not that this is the point of the question, but we all know that the real problem with PALs and tropias is dealing with monocularity (d/t amblopia or suppression). Chipster, do your prosthetic patients do poorly with PALs? I find that a high percentage of monoculars do fine with PAL.

[chip anderson]

Actually my prosthetic patients can't fuse at all with PAL's. But then they don't seem to be able to do much better with lines or SV's for that matter.

All of them seem to suppress vision on one side for some reason.

Chip

[braheem24]

Prosthetic patients and fusion are we still typing in English?

[Wes]

Prosthetic patients and fusion are we still typing in English?

That left me wondering as well...

[drk]

I guess that's what I get for trying to include you, Chip.