I am going to cross post this message as it is extremely important for strabismics and for parents of strabismic children seeking prism lenses.
This is especially important in Pennsylvania where the counter people do not have to be licensed opticians. For strabismics, you can get yourself really hurt. For normal folks, you can go round and round trying to get your glasses straightened out especially if you use the chains like Sears or Pearl Vision. In New Jersey, however, you MUST be a licensed optician to sell eye glasses.
Be extra careful when ordering prism glasses as some opticians have no idea what to do with strabismic patients and may calculate their own pupillary distance (PD) measurement that will not be the same as the developmental optometrist's PD. The difference in the PD measurement can have disastrous effects on your prescription. Although Luxottica Retail says they'll change their training programs for their opticians after my incident, I don't know if they really will. Even if you go to non-Luxottica owned optical stores, make sure the optician doesn't override your doctor's prescription because of the "Standard Operating Procedure" for measuring PD.
I am not exaggerating when I say that what I experienced could have been fatal. Below is the description of what happened to me.
After two and a half LONG years in VT, I finally got a prescription for prism glasses in mid May. I went to Sears Optical to fill the prescription and after a long delay in making my lenses, I received a pair that almost caused me to crash my car because the pupillary distance was incorrectly calculated by the optician.
Effect: I had to drive with one eye closed because my left field of vision moved faster than my right field. The divider lanes on the left doubled at a 20 degree angle into my lane, causing me to get confused as to where my lane was. At night, the extra divider lane was not only at a 20 degree angle but it was sometimes elevated above ground. If you've ever had to drive with an eye closed, you know how hard it is.
I couldn't look down when descending a staircase because the end of the step would also double at a 20 degree angle, making it hard for me to see where the end of each step was. Other lines, whether they be on sidewalks or my kitchen floor, would double or be distorted.
I went round and round trying to get progressive lenses straightened out here in PA before I got a referral for an optician in NJ who got them straightened out.
MIL went to a chain and we went back and forth a number of times until I gave up and went to NJ.
For my prisms, I did go to an optician in PA but only the one recommended by my developmental optometrist.