What type of ultrasound should I order for a patient with blurry vision in the Emergency Department (ED)?

Ocular Ultrasound for Blurry Vision in the Emergency Department

For patients presenting with blurry vision in the Emergency Department, a B-scan ocular ultrasound should be ordered as the appropriate type of ultrasound examination. 1

Rationale for Ocular Ultrasound in the ED

Ocular complaints represent up to 3% of all Emergency Department visits, with blurry vision being a common presentation that could indicate serious pathology requiring prompt diagnosis and treatment 2. Point-of-care ultrasound (POCUS) has emerged as a valuable diagnostic tool for emergency physicians evaluating patients with ocular complaints.

The American College of Emergency Physicians (ACEP) specifically identifies ocular ultrasound as one of the core emergency ultrasound applications in their guidelines 1. This recognition underscores its importance in the emergency medicine armamentarium for rapid bedside diagnosis.

Technical Specifications

When ordering an ocular ultrasound for blurry vision:

• Transducer type: Use a 10-MHz linear-array transducer 3
• Technique: Examination should be performed through a closed eyelid using water-soluble ultrasound gel 3
• Views: Both eyes should be examined for comparison, even if symptoms are unilateral

Diagnostic Capabilities

B-scan ocular ultrasound can identify several important pathologies that cause blurry vision:

• Retinal detachment - appears as a highly reflective membrane floating in the vitreous 2, 3
• Vitreous hemorrhage - appears as mobile echogenic material in the vitreous cavity 3
• Vitreous detachment - appears as a mobile, thin membrane within the vitreous 3
• Lens dislocation - visible displacement of the lens from normal position 3
• Globe rupture/penetrating injuries - disruption of the normal globe contour 3
• Optic nerve abnormalities - including optic perineuritis which appears as a highly reflective circle with shadowing around the optic disc 4

Clinical Algorithm for Use

1. Order B-scan ocular ultrasound when:

   • Patient presents with acute or sudden blurry vision
   • Direct visualization of fundus is difficult or impossible
   • Suspicion of retinal, vitreous, or other posterior segment pathology
   • Trauma to the eye with visual changes

2. Interpret results promptly:

   • Positive findings requiring immediate ophthalmology consultation:
     • Retinal detachment
     • Globe rupture
     • Lens dislocation
     • Central retinal artery occlusion
   • Findings that may allow for outpatient follow-up:
     • Vitreous detachment without retinal involvement
     • Mild vitreous hemorrhage without retinal detachment

Evidence of Efficacy

Emergency bedside ultrasound has demonstrated high accuracy in diagnosing ocular pathology. In a prospective study, emergency physicians correctly identified ocular pathology in 60 out of 61 cases when compared to the criterion standard examination 3. This high level of accuracy makes it an excellent initial diagnostic tool in the ED setting.

Pitfalls and Limitations

• Requires proper training and experience to perform and interpret accurately
• May not detect subtle retinal tears without detachment
• Cannot replace comprehensive ophthalmologic examination for definitive management
• Excessive pressure should be avoided, especially when globe rupture is suspected

Integration with Other Diagnostic Modalities

While ocular ultrasound is an excellent first-line diagnostic tool, it should be followed by:

• Orbital CT for suspected foreign bodies or orbital fractures
• Complete ophthalmologic evaluation for confirmation and management of identified pathology 3

B-scan ocular ultrasound represents a rapid, non-invasive, and accurate method for evaluating patients with blurry vision in the emergency setting, allowing for prompt diagnosis and appropriate consultation or referral based on findings.