Chapter 23: Ocular

INTRODUCTION

Ultrasound of the globe and orbit can be a valuable tool in evaluating patients with serious eye complaints. Its benefit can even be extended to those with concerns for increased intracranial pressure (ICP). In many acute ocular conditions, the physical examination is difficult and often unreliable. Specialized equipment and ophthalmologic consultation are frequently unavailable in the emergency department (ED). In many circumstances, ultrasound is more accurate than traditional examination techniques for assessing a wide variety of ocular and orbital diseases, including penetrating globe injuries, retinal detachment, and papilledema.¹⁻⁴

The eye is an ideal structure for ultrasound interrogation since the anterior chamber and vitreous cavity are fluid filled. The globe, orbit, and retrobulbar structures can be evaluated accurately and safely.² While ophthalmologists typically use highly specialized ultrasound transducers, point-of-care ocular ultrasound is performed using transducers readily available to acute care providers.⁵⁻⁸ The power of ocular ultrasound is in its ability to aid the clinician in differentiating between pathology requiring immediate ophthalmologic consultation and that which can be followed up on a nonemergent basis.

CLINICAL CONSIDERATIONS

Ophthalmoscopic and slit lamp examinations are the primary diagnostic approach to most ocular complaints. There are many situations in which the physical examination may be limited requiring further diagnostic evaluation. Ultrasound examination of the eye is useful in many situations encountered in acute care settings. As the standard physical examination requires a clear visual axis to examine the structures of the eye, any obstruction, such as blood in the anterior chamber or vitreous, limits the clinical evaluation. Ultrasound allows imaging beyond the obstruction. Even when direct visualization is difficult or impossible (e.g., vitreous hemorrhage), there is little attenuation of the sound waves, allowing detailed, high-resolution images of posterior structures of the eye.

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, which may be painful and even harmful if there is globe perforation. Visual axis obstruction can also occur in the presence of corneal scars, cataracts, hyphema, 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. One example is a retinal detachment. Patients presenting with historical features consistent with a retinal detachment may have an unremarkable limited eye examination. A comprehensive examination including pupillary dilation is not always practical in the acute care setting. Ultrasound allows for visualization of the entire retina without dilation of the pupil.

Computed tomography (CT) is frequently employed to evaluate the globe after trauma. CT is highly sensitive for orbital fractures, foreign bodies, vitreous hemorrhage, and retrobulbar hematomas, but ...