01 Use a high frequency linear array transducer (10-13 MHz).
02 In most instances, you can place the ultrasound gel directly onto the patient’s closed eyelid to facilitate the exam. You can also place a small Tegaderm dressing over the patient’s eyelid and then apply the gel over the Tegaderm if you want to prevent any contact between the gel and the patient’s eye. The Tegaderm will not pull off eyelashes or eyebrow hairs when it is removed, and it is thin enough to use as a protective eye shield during your scan.
03 If your ultrasound machine does not have an ocular setting, you can use the nerve or small parts setting during your scan.
04 The eye is a great organ to ultrasound. It is a fluid filled structure that provides excellent visualization of the anterior chamber, the lens, the pupil, the posterior chamber, the posterior globe, and the optic nerve.
05 To evaluate the posterior chamber for vitreous hemorrhage or retinal detachment, turn up the gain to achieve the best images.
06 You can perform a periorbital scan to evaluate for cellulitis, abscess, foreign body, or mass. Use plenty of gel to ensure you have a good acoustic window and to minimize air pockets between your probe and the area of interest.
07 Periorbital abscesses will appear similar to other soft tissue abscesses on the body. As you scan towards the area of interest, look for a spherical or elliptical collection of hypoechoic or heterogeneous material. The fluid collection may have a bright, hyperechoic border/capsule along the edges.
08 Abscesses may appear hypoechoic or anechoic during the initial stages of formation. As the inflammatory process progresses, the pus may begin to appear more heterogeneous with a mix of hypoechoic and hyperechoic material swirled together.
09 Differentiating between cellulitis and small abscess pockets may be difficult. Apply a small amount of pressure over the area of interest. Fluid collections secondary to cellulitis will redistribute with pressure. Abscess pockets will not diffuse under pressure.
10 Always obtain images in multiple planes (longitudinal, transverse, oblique) to help define the borders. Use the calipers on the ultrasound machine to calculate the dimensions of the abscess pocket.
11 Utilize contralateral organs and adjacent areas of normal appearing tissue for comparison.
12 With bedside ultrasound, there is no substitute for experience. The more scans you do, the better you will be able to differentiate abnormal from normal, even when you may not be sure exactly what the abnormality is.