Intro: Vertigo Diagnostic Goggles (a Poor Therapist's Frenzel-type Lenses)
So by this point, any PT not working at a vestibular clinic has looked forlornly at branded Frenzel Lenses and IR Goggles and tried to decide if diagnostic accuracy is worth the time spent trying to convince the budgetary committee that these are with the $500-4000 price tags.
Unless your clinic sees enough vestibular patients to justify that cost, you may need to look elsewhere. Enter the fresnel lens goggles (above left). All you'd need are some old chem lab goggles, athletic tape, and two fresnel fire starter lenses. They'll run you about $5, and are super easy to make. While only one group has studied whether or not “take away lenses” share the diagnostic accuracy of IR Goggles, that group found no significant difference, and you at least won't break the bank.
The other downside you'll find is that they look a little bit iffy as far as professional equipment goes. If you haven't had a patient who criticizes this yet, be patient. They're out there. Waiting.
While using Virtual Reality Goggles on one of my clinicals with motion intolerance patients, I discovered that thanks to the Google Cardboard these are super cheap and easy to come by. If you haven't picked some up yet for your visually dominant patients, I highly recommend it. Now me being me, I wanted to take mine apart as soon as they came. So I did. Turns out, their lenses are 20-25 diopter magnifying glasses meant to magnify your smartphone's screen (the same required for true Frenzel goggles). Now because physics is a jerk, by my understanding that means that they won't come out to the full 20 diopters looking back at the eye for us since focal distance comes into play, but neither do the fresnels regardless. So, here's what I did. It's super simple, and you should be done within about 10 minutes, 30 if you're stuck with hand tools.
Step 1: Get You Some Goggles
I grabbed some cheap VR goggles online by searching for "Google Cardboard" goggles. The low end Sunnypeak VR goggles and iDudu Minis are some of the simplest models I've found: very few pieces, look decently professional, and only run about $10 on Amazon. To boot, the housing on the Sunnypeaks is plain plastic with no foam covering, so easy to disinfect between patients. It's not the most comfortable thing in the world, but cleaner is better to me.
There are other types goggles out there that have a hinged enclosed housing that is far more secure for your phone. These were my initial experiment into this. You'll be in for a lot more cutting with a power tool and an uglier end product, but you'll still get magnified eyes, so it's all up to you because sometimes they're even cheaper. Those do produce a little different quality image in regards to the Virtual Reality experience, so on that end they might be worth picking up for you, but for this simpler is better.
Step 2: Remove the Phone Clip
With this model of goggle and the others with the simple slide in clip, all you'll need to do is remove that front panel designed to hold in your phone. I used a rotary tool cutting wheel, so it took me all of a minute. If you don't have a tool like this, or a friend with one, a hacksaw should do you just fine. It will take you longer, but that's really the worst of it.
Step 3: Sanding and Finishing
If you want at this stage, you can be done. Personally I thought the edges were a little rough. This part is pretty obvious, if you want to sand down the edges: do it. I used my rotary tool again (cosplayer perks) with its sanding drum, but again if you do it by hand you'll be fine. You can rubberize over this with Plasti-Dip or another rubberizing spray for a complete finish too as this will fill in any scratch marks from sanding and cutting, plus it will give you a nice uniform color in case they used multiple plastics for the original goggles.
Step 4: And There It Is...
You're done. Should have been a nice quick project. A standard clinical pen light will cover for illumination if your clinic lighting is bad or your patient is attempting to spot an object to stop their nystagmus, but otherwise that's it. Get a cheap set of VR goggles, cut off the front, sand, and finish. I've gotten very good magnification with my patients, and the lenses alone seem to block patient clarity enough to stop focusing in my experience (admittedly I'm a young therapist so that experience is limited, plus we all know clinical experience isn't an RCT). Good luck!