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?
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