In many acute ocular conditions, physical examination can be difficult and unreliable; persistent efforts to examine the eye may also be deleterious to the patient. Specialized equipment and ophthalmologic expertise are frequently unavailable, particularly during nontraditional business hours. In these circumstances, ultrasound can be an important tool for assessing a wide variety of ocular and orbital diseases, including penetrating injuries, retinal detachment, and evaluation for papilledema.chch17rf1,chch17rf2,chch17rf3
The eye is an ideal structure for ultrasound interrogation since the anterior chamber and vitreous cavity are essentially fluid filled. With ultrasound, the globe, orbit, and retrobulbar structures can each be evaluated accurately and safely.2 Because a cooperative patient can move the eye, all aspects of the globe can be evaluated when coupled with transducer angulation and movement. While ophthalmologists typically use highly specialized ultrasound transducers in their clinics, ocular ultrasound may be performed using transducers readily available to physicians using bedside ultrasound.chch17rf4,chch17rf5,chch17rf6 This technology accurately differentiates between pathology requiring immediate ophthalmologic consultation and that which can be followed up on an outpatient basis.
Physical examination incorporating ophthalmoscopic and slit lamp examination is the primary diagnostic approach to most ocular complaints. There are many situations in which the physical examination may be limited and imaging is required. Ophthalmologists have been using ultrasound to examine the structures of the eye for decades, while emergency physicians have reported only the utility of ocular ultrasound in the past 5 years.2, 7
Ultrasound examination of the eye is potentially useful in many situations encountered in emergency or acute care practice. Since physical examination requires a clear visual axis to examine the structures of the eye, any obstruction that obscures this visual axis also limits physical examination. Ultrasound allows imaging beyond the obstruction. There is little attenuation of the ultrasound signal. Detailed, high-resolution images can be obtained of posterior structures even when direct visualization is difficult or impossible.
Situations in which direct visualization of intraocular structures may be difficult or impossible include lid abnormalities due to facial trauma, severe edema, subcutaneous air, or previous surgeries. In cases of facial trauma and swelling, it may be difficult to assess the eye without significant manipulation that can be painful and even harmful if there is globe perforation. Visual axis obstruction can also occur in the presence of corneal scars, cataracts, hyphema, or hypopyon, or with vitreous hemorrhage. Furthermore, normal conditions such as miosis make visualization of the retina difficult without pharmacologic agents.
Ultrasound may also be helpful in situations where physical examination alone is inadequate. An example is peripheral retinal detachment. Patients presenting with a history consistent with retinal detachment may have an unremarkable ophthalmologic examination. However, performing an examination of a dilated pupil is not always feasible. Ultrasound allows for visualization of the entire retina.
Computed tomography (CT) is frequently employed for evaluating the globe after ...