Why perform an ocular ultrasound?

• Honestly, it’s a debated topic. I suppose it also depends on your relationship and availability with your ophthalmology department… and your comfort with a good old-fashioned fundoscopic exam.

• The most common application is the detection of retinal detachment, vitreous detachment, and vitreous hemorrhage.

  • So: patients with painless vision loss OR patients with flashes/scotomas.

  • The absence of the above pathologies in a patient with painless vision loss consequently increases the likelihood of temporal arteritis (so check ESR, CRP), central retinal artery occlusion (so get an ECG), central retinal vein occlusion, and possibly optic neuritis.

  • Roughly speaking, the ultrasound helps us move from a “slam dunk” diagnosis to one that we need to investigate further before calling ophthalmology.

• Other, more situational applications: testing the pupillary reflex / DPAR in a patient whose eye is not accessible (often due to traumatic eyelid edema), or looking for a lens dislocation.

• Other, more controversial applications: looking for papilledema or foreign bodies (which would have already perforated the eye…).

How to perform an ocular ultrasound?

1. Clean your linear probe (which, until proven otherwise, may have just been used to evaluate a scrotal abscess).

2. Place a Tegaderm over the patient’s closed eye (even if you’ve cleaned your probe! If I were the patient, I’d still want a barrier between my eye and the probe for obvious reasons).

   1. Interestingly, we’ve found that applying the Tegaderm horizontally molds better to the orbit and generates fewer artifacts.

3. Apply LOTS of gel over the Tegaderm. (It makes the exam much more comfortable and minimizes pressure—you should NOT press on the eye!).

4. Stabilize your hand either on the nose or zygomatic bone, depending on your dominant hand and which eye you’re examining.

5. Start in the transverse orientation with the eye still, sweeping from cephalad to caudal to look for the optic nerve and retinal/vitreous abnormalities.

   1. The optic nerve is a very important landmark in ocular pathology assessment. You MUST identify it.

6. Stop sweeping and stay still, then ask the patient to look left and right continuously for 10 seconds → this induces vitreous movement and helps identify detachments or hemorrhages more easily.

   1. (See article below — it can also be interesting to evaluate the orbit at different gain levels.)

7. Switch to a sagittal orientation, sweep right to left, return to center, then again ask the patient to look right and left for 10 seconds. Done.

8. It can be helpful to compare with the contralateral eye.

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Very interesting article on optimizing gain in ocular ultrasound:

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10284517/

• TL;DR:

• The higher the gain, the higher the sensitivity—but the lower the specificity.

• A medium-to-high gain setting is generally recommended.

• And remember, no matter your gain setting, your ultrasound is still imperfect!

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What does it look like?

Anatomy of the eye: