Thursday, June 14, 2012

You'll shoot your eye out, kid! - Ocular Ultrasound

The Gist:  Ultrasound (US)  training is a vital part of Emergency Medicine (EM) education and may play an even more important role in military, community setting.  Ocular US may prove especially useful in diagnosing and triaging patients with ocular trauma, particularly with regard to retinal detachment in the aforementioned settings.

Recently, EM folks on Twitter debated the utility of ED US in retinal detachment. Those arguing against US dismissed the modality due to the need for an opthalmology consult regardless of the US findings.  This reminded me of a strikingly similar debate I had with a budding PGY-1 ophthalmology resident.  Their arguments have some validity; however, I think it's easy to get swept away in the comfort of 24/7 consults in the academic hospital atmosphere.  This isn't available everywhere, even in the United States, but knowing when emergent action is warranted could prevent serious morbidity.  As the "jack of all trades," EM physicians should probably be prepared for wherever their careers may land them. 

  • Case report from the military of a patient who suffered a ricochet gunshot wound to the face from an AK-47 who was initially treated for a laceration just inferior to his medial canthus.  Over the subsequent days his vision deteriorated and he was found to have a closed globe with a sluggish pupillary response to light.  Bedside US confirmed retinal detachment and the patient was transported to a combat hospital for ophthalmology care.  He did not recover his visual function in that eye.
  • The article is a pretty good read as it succinctly highlights some of the technical aspects of US for retinal detachment with photos and textual descriptions.
This case study suggests:
  • Bedside US in the emergency setting can rapidly identify retinal detachments.
  • There is likely an incredible role in the battlefield and other remote areas.
  • Facial trauma may result in ocular trauma, which isn't immediately apparent and may have permanent deleterious consequences.  Perhaps this patient's vision could have been saved if ocular US had been performed on his first visit.
How do I do this? 
  • As always, check out Ultrasound Podcast's amazing Ocular Ultrasound podcast featuring Dr. Chris Fox (Ultrasound Master from UC-Irvine).  Retinal detachment discussion begins at 17:45 .  They've got everything you need to be able to get started with ocular US (and handy instructions on the One Minute Ultrasound app, naturally).
  • Pearls from Dr. Chris Fox:  
    • Ensure you're dealing with a closed globe and make sure you're scanning with the eyelid closed, of course.
    • Use tons of chilled gel (reduces pressure and the high-frequency linear transducer 7.5-10 MHz
What does US really add..besides instant gratification?
  • US can differentiate between a "mac on" and "mac off" retinal detachment, which is huge for prognosis.  Instances where the macula of the retina is not detached (mac on) is an ophthalmologic emergency.  If these aren't treated immediately, patient's can deteriorate into a "mac off" detachment, which can result in permanent vision loss (as in the patient featured in the case study).  In resource limited settings or remote areas, this may be an important way to determine patients that must immediately see an ophthalmologist from those who occupy a less precarious situation (sometimes resource allocation is an issue)
    File:Human eye cross-sectional view grayscale.png
(Image from Wikipedia)
  • Also, ED physicians are pretty good at identifying retinal detachment, with a prospective study (n=48, with 15 EM physicians performing US) demonstrating sensitivity and specificity for RD of 100% (95%CI = 78% to 100%) and 83% (95% CI = 65% to 94%), respectively. 
  • US in resource limited settings is feasible and growing in importance so if one is interested in disaster medicine or global medicine, this is a great skill to have.  Check out Mount Sinai's recent US education trip to Haiti, this article discusses US training in Rwanda (and there are many more like it).  

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