A quick case that shows how we can use ultrasound in clinical assessment of eyes and why US makes me look like a better doctor.
30 year old woman – was punched in the face 3 days ago at a disco. She sustained a small laceration over the inferior orbital rim – but went on dancing.
The next day she awoke with a really swollen face, unable to open her eye at all. The laceration had sealed itself – so she decided to wait a few days to “see it it would get better”. That is the type of people we see a lot of in Broome!
By day 3 the swelling was no better and she was beginning to get a bit annoyed by the pain and inability to open her eye… so off to ED.
The left eye was severely swollen – despite analgesia and a firm hand – the best I could do was glimpse the sclera and a bit of cornea. She had a small subconjunctival haemorrhage, no hyphema and a clear looking cornea [in the half second that she tolerated my prying her lids apart.] Far from an ideal assessment. So how do you assess an eye that is occluded by swelling in the middle of the night? Ultrasound of course!
Here is a rough guide to looking into eye trauma using the US machine.
- Linear probe set to 4 – 5 cm depth. “Small parts” preset works OK.
- Get heaps of gel onto he probe / upper lid (use cooled gel if you want to make a gel heap as a stand-off pad.)
- Easiest to have the patient supine with pillow to stop the head moving.
- Set the gain to make the vitreous black, however it can be useful to turn it up if you are looking for subtle intra-vitreal bleed etc
- Scan over the upper lid fanning from superior to inferior, then in sagittal plane from side to side.
There are some cool things you can do with ocular US when the eye is unexaminable:
– Assess range of extra ocular movement. This is really important for assessing for rectus entrapment.
– Assess pupil response (check out the video here)
So I went through my routine and scanned the closed eye. In trauma I look for the following injuries on my scan:
- lens dislocation,
- retinal tear,
- intra-vitreal bleed / detachment,
- globe rupture and
- retrobulbar haematoma [tip is a "guitar pick-shaped" posterior globe]
- Check the optic nerve sheath diameter (ONSD)
As I was scanning the orbit I kept getting this weird artefact – thought it was maybe due to some cellulitis or loss of contact – but it “just didn’t look right”.
So when I do a scan and it is “not quite right” I tend to imagine the worst case scenario. I was seeing a normal eye with good pupil response, extra ocular movement etc. No pathology – just this odd artefact that obscured my views. So I decided to investigate further.
Here is the CT of her orbit: Clearly an inferior orbital fracture with a nice teardrop of fat extruding into the antrum.
And you can see quite a bit of air that has escaped into the orbit – which was the source of my mystery artefacts.
So I thought I had just discovered a new sonographic sign – but of course I was wrong.
There was a paper published on this phenomenon way back in AJEM, 2004 from Michael Blaivas et al (here)
So I managed to fluke finding air in the orbit – though I wash’t really sure what I was seeing!
Lessons learned here:
- If you are not sure what you are seeing – don’t ignore it! It might be the key to the diagnosis
- Air in the orbit equals blowout fracture and looks like a dirty gas shadow (kinda like bowel in the orbit)
- Correlate your bedside scan with formal images and you will learn a lot faster.