Emergency physician–performed ocular ultrasound is a rapid and reliable way to evaluate the anterior and posterior chambers of the eye for a variety of emergent conditions, including lens dislocation, intraocular foreign body, and retinal and posterior vitreous detachment. It is particularly useful in the setting of ocular trauma when a direct fundoscopic examination is needed, but difficult or impossible to obtain.
Equipment: Recommended Transducers for Ocular Ultrasound
High-frequency linear array
It is important to select the “ophthalmic exam setting” or confirm and then adjust the energy output levels of your ultrasound system that are approved for ocular ultrasound.
With the patient lying supine, place a liberal amount of gel on top of the patient’s closed eyelid. The orientation marker should be directed toward the patient’s right for transverse images and cephalad for sagittal images.
The probe should exert little to no pressure on the patient’s eye. This is accomplished by stabilizing your fingers on the bridge of the nose (when imaging the right eye) or the zygomatic arch (for the left eye) (Fig. 24.124A,B).
FIGURE 24.124A, B
Ocular Ultrasound. Place a liberal amount of gel on top of the patient’s closed eyelid. The orientation marker should be directed toward the patient’s right for transverse images and cephalad for sagittal images. The probe should exert little to no pressure on the patient’s eye. (Photo contributor: Lawrence B. Stack, MD.)
Transverse and Sagittal Views
With the indicator pointing toward the patient’s right, identify the anterior chamber, lens, posterior chamber, retina, optic nerve, and retrobulbar space (Fig. 24.125).
The probe should be fanned back and forth to ensure that the entire retina is visualized.
The overall gain should be increased to assess for evidence of hemorrhage or vitreous detachment in the posterior chamber.
If assessing for elevated intracranial pressure, the optic nerve sheath diameter (ONSD) should be measured 3 mm from the retina (Fig. 24.126). If measuring the ONSD, it is essential to ensure that the plane of the ultrasound beam is not tangential to the optic nerve.
The eye should be imaged in both the sagittal and transverse planes to increase the accuracy of detecting pathology, particularly retinal detachment.
Ocular Ultrasound. Normal eye anatomy. (Illustration contributor: Robinson M. Ferre, MD; ultrasound contributor: Robinson M. Ferre, MD.)
Ocular Ultrasound. The ONSD is measured 3 mm from the retina. ...