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Ocular Ultrasound: EM Physicians are OK but not Perfect at Diagnosing Common Pathology

By Joshua Guttman, MD

Baker N, Amini R, Situ-LaCasse EH, et al. Can emergency physicians accurately distinguish retinal detachment from posterior vitreous detachment with point-of-care ocular ultrasound? Am J Emerg Med. 2017 Oct 13. pii: S0735-6757(17)30814-8.

Ocular complaints are common in the ED. Particularly, it is common for patients to present with visual disturbance, flashes and floaters. The most common causes of these complaints are posterior vitreous detachment and retinal detachment. Posterior vitreous detachment (PVD) is a relatively benign cause that does not require urgent ophthalmologic intervention, while retinal detachment (RD) is a site-threatening and requires urgent consultation. Traditionally, emergency physicians relied on a dilated ophthalmologic exam by an ophthalmologist to differentiate between these two conditions. Ultrasound has been suggested as an alternative method that can be performed at bedside, without the aid of an ophthalmologist. Previous studies on experts showed that point of care ultrasound (POCUS) was able to rule out RD with a high degree of accuracy. Ultrasound can also be used to identify PVD, differentiating it from RD.

The authors of this study sought to determine the ability of emergency physicians at various levels of POCUS experience to differentiate RD, PVD and normal ocular POCUS based on video image review. They enrolled residents and attendings who all had basic POCUS knowledge but had variable proficiencies in ocular POCUS. They were all given a brief tutorial on differentiating PVD and RD. The gold standard was the diagnosis given by the consulting ophthalmologist for those specific cases. Overall, 390 video clips were reviewed by 13 physicians. They diagnosed RD 74.6% of the time, PVD 85.7% of the and normal 94.9% of the time. There was no statistically significant difference between physicians with more or less experience (0-25 scans vs 25-50 vs over 50) or by level of training (attending, fellow or resident).

This study showed that emergency physicians had modest accuracy at differentiating PVD and RD on ultrasound. There were several limitations to this study, including the limited number of participants, the bias towards only 3 possible diagnoses on POCUS (PVD, RD and normal) as opposed to the wider differential diagnosis in normal clinical practice, and that it was run at an academic medical center with likely more savvy POCUS staff. The more interesting aspect of this study was that there was no difference in accuracy based on the number performed. It is generally assumed that the more POCUS exams done, the more proficient one is at interpretation. However, in the case of ocular ultrasound this may not be accurate. Fortunately, emergency physicians at all levels were able to diagnose a normal ocular ultrasound which can be helpful in the clinical setting. However, the moderate diagnostic accuracy is not sufficient to rule out RD and therefore a non-expert still needs ophthalmologic consultation.

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