Here in my second year at Southern College of Optometry, I feel like I have the basic binocular testing down pat. Well, my skills may not be perfect, but in comparison to scleral depression and peripheral views in BIO, I feel pretty comfortable. As we improve our binocular testing techniques, we may get to the point where we place these skills on autopilot. Unfortunately, this can mean we sometimes leave details in the dust. Although it can be a great help practicing with your classmates, the average optometry student’s binocular system is typically fairly normal, leaving little opportunity to work through challenging cases. Have no fear, though, because I am certainly an outlier!
As a convergency insufficient (CI) and exotrope patient, I have a few pearls for binocular testing that I get to share with my lab partners. Hopefully, my spiel filled with simple tidbits will help prepare you for the next time you have a difficult patient!
- Slow down on unilateral cover test (UCT)
This is the number one piece of advice I wish I could say to every optometry student. I am a 12 prism diopter constant alternating exotrope (CAXT) at near, but it is often missed because of how quickly clinicians sometimes rush through UCT. If we uncover and then re-cover too quickly, there is a chance that the patient never fixated the target with the uncovered eye. It’s easy to check and see that the eye stayed pointing at the wall when the patient is a 24 prism diopter CAXT, but it’s not as simple when the angle of deviation is not as large. Be sure to give the patient enough time to re-fixate on the target!
- Take it easy on that prism wheel, too.
With phorias and vergences, it’s easy to accidentally influence the results by rotating the phoropter wheel a little too quickly (especially on vertical vergences, which I am guilty of). Look, it would be great if everyone was orthophoric, but we do our patients no favors when we don’t slow down to get accurate and reliable phoria and vergence values. Furthermore, while evaluating phorias and vergences, be sure to ask pertinent questions before the test begins, such as:
- Do you see two images?
- Is one image up and to the right and the other image down and to the left?
- Is the image single and clear?
- Test again, and again, and again…
Have you ever had a patient whose binocular system test results appear out of whack? Although they appear to be ortho, they complain about double vision or asthenopia while reading. I have a tip for you – just keep going! Perform an alternating cover test for a few extra cycles. The patient may eventually start to break down. No luck? Try doing the test with a slightly dissociating filter, like placing a red or polarizing lens over one eye of the patient. It may be just enough to break down their fragile system. If all else fails, perform the rest of the exam and come back to phorias or cover test later to evaluate if their binocular system tires out. I know some of these tips might sound silly, but they have all worked on me at some point!
- Clean your prism bars! (But not with alcohol wipes!)
This one is easy to forget, but your patient can’t tell whether something is clear and single if they’re trying to fixate through a greasy cloud. Just remember that alcohol wipes can damage the coating on your prism bars. For regular smudges, use a clean microfiber cloth. For heavier messes like mascara, mild soap and water should do the trick. Face oils are gross. The last patient’s makeup is gross. Clean your prism bars!
- If it looks like a CI, and quacks like a CI, throw in some plus to be sure!
We know pseudo-CIs are more like zebras than horses in the clinical world, but if the accommodative amplitudes approach minimum average values, consider adding a diopter of plus in the phoropter and re-testing. If amplitude values improve, your patient more than likely is a pseudo-CI. Using plus lenses to alleviate patient symptoms can save lots of time compared to doing vision therapy.
Well, that’s all the advice I’ve got! It all boils down to being thorough and knowing when to spend a little extra time on a situation so we can care for patients to the highest level. Here’s some more articles to wander through if you’re in a binocular vision mood!