Emergency Medicine News:
The Speed of Sound
Dr. Butts is the director of the division of emergency ultrasound and a clinical assistant professor of emergency medicine at Louisiana State University at New Orleans.
A 20-year-old man presents to the ED after being hit in the eye. He complains of some pain to the area and of a blind spot in his vision. An exam reveals some mild swelling to the periorbital area, but the globe itself appears normal, the pupil is reactive, and extraocular movements are normal.
Visual acuity is 20/40 and equal to the contralateral eye. A visual field deficit is present to the nasal field of the affected eye, however. An ultrasound of the affected eye is shown.
A retinal detachment can easily be missed by the emergency physician. These are traditionally thought of as resulting from trauma to the eye, but many detachments occur as the result of chronic disease, such as diabetes. Patients typically complain of visual defects, such as visual field deficits or floaters and flashing lights. Some patients may only perceive a decrease in their vision. Physical exam may be challenging for the EP and not result in a diagnosis. Finding a visual field deficit on confrontation testing is highly suggestive of a detachment, but directly identifying a detachment with fundoscopy is often difficult and may be impossible. Ultrasound of the eye is a simple technique that can quickly identify a number of pathologic findings, including retinal detachment.
A high-frequency transducer should be used to perform an ultrasound of the eye so the clinician can obtain adequate resolution to visualize the superficial structures of the eye. A large “pillow” of gel should be placed on the patient's closed eyelid to provide increased resolution. Care should be taken to avoid placing pressure on the eyelid, especially in trauma, until an open globe can be ruled out. Placing the heel of the scanning hand on the patient's forehead can aid in allowing the EP to place the transducer on the gel pillow with minimum pressure. The globe is easily recognized on exam; it appears as a circular object with identifiable structures. (Image 1.) The globe should be evaluated thoroughly in the transverse and longitudinal planes to assess for detachment.
Image 2: An ultrasou...Image Tools
A detachment appears as a hyperechoic (white) membrane along the posterior aspect of the globe. (Image 2.) The size of the detachment will determine how large the membrane appears and how apparent it is on ultrasound exam. Small detachments may be subtle. It may be necessary to increase the gain to visualize a detachment adequately, but increasing the gain can also increase the artifacts that can resemble a detachment. Fortunately, differentiating between artifact and the membrane of a detachment is straightforward. While viewing the questionable membrane, the patient should be asked to move the eye by looking right and left. The membrane of a retinal detachment will appear to “wave” or undulate within the vitreous, and an artifact will remain fixed.
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