Orbital Ultrasound

Aka: Orbital Ultrasound, Ocular Ultrasound, Eye Ultrasound, Globe Ultrasound, Optic Nerve Sheath Diameter, Pupil Exam with Ultrasound

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II. Contraindications

  1. Globe Rupture
  2. Retrobulbar Hematoma

III. Preparation

  1. Equipment
    1. Ultrasound with Linear array high frequency transducer (7.5 to 15 MHz)
    2. Set Ultrasound to ophthalmology preset (or small parts preset)
  2. Prepare eye
    1. Patient closes eye lids and copious amounts of Ultrasound gel are applied to the surface of Eyelid
    2. Bio-Occlusive Dressing may be applied over the eye lid first to protect from the gel
      1. Optional as most patients tolerate the gel over the Eyelid (similar to gels used as make-up remover)
  3. Precautions
    1. Avoid prolonged Ultrasound to reduce mechanical and thermal forces on the eye
    2. Use copious amounts of Ultrasound gel to avoid excessive eye pressure with probe

IV. Exam

  1. Apply gentle pressure to the eye
    1. Stabilize the transducer (and minimize pressure) by bracing hand against the patient's Nasal Bridge, eye brow or zygomatic arch
  2. Survey the eye in 2 planes
    1. Start in longitudinal orientation (marker at 12:00)
      1. Gradually sweep by tilting from medial orientation to lateral orientation
    2. Rotate to transverse position (marker at 9:00)
      1. Gradually sweep by tilting from superior orientation to inferior orientation
  3. Additional techniques
    1. Consider Ultrasounding both eyes to allow for comparison
    2. See Pupil Exam with Ultrasound as described below
    3. Patient may also be asked to move their eye in a particular direction
      1. Allows for examiner to reposition areas of concern into a better view on Ultrasound
      2. Allows for Extraocular Movement evaluation despite closed Eyelids
  4. Ultrasound landmarks
    1. Cornea
      1. Smooth hyperechoic line
    2. Anterior chamber
      1. Anechoic, fluid filled cavity
    3. Lens
      1. Hyperechoic and biconvex
      2. May generate reverberation artifact into the vitreous chamber region
    4. Vitreous chamber
      1. Regular shape, anechoic chamber
      2. No hyperechoic or bright contents normally (outside of possible lens revereberation artifact)
    5. Retina
      1. Smooth, hyperechoic line at posterior globe
    6. Optic Nerve sheath (see Optic Nerve Sheath Diameter below)
      1. Dark, vertical wide line eminating from the posterior globe

V. Evaluation: Observe for eye and orbital pathology that can be found on Ultrasound

  1. Ultrasound artifacts
    1. May at first appear as atypical substance within the vitreous
    2. Will not move with eye motion
    3. Will not respect globe boundaries
  2. General eye findings
    1. Intraocular foreign body
      1. Appears hyperechoic within vitreous
      2. Some foreign bodies may posterior shadow (similar to Gallstones)
    2. Globe Rupture
      1. Avoid any pressure on globe if rupture is suspected (stop scan immediately for positive findings)
      2. Collapsed anterior chamber (lens abuts lid with loss of rounded Cornea)
      3. Irregularly shaped posterior chamber
      4. Scleral buckling
      5. Vitreous Hemorrhage
  3. Anterior chamber pathology
    1. Afferent Pupillary Defect (see below)
    2. Lens Dislocation or Lens Subluxation
      1. Biconvex or round displaced object into the vitreous chamber
      2. May be free-floating if fully dislocated
  4. Posterior chamber pathology
    1. Vitreous Hemorrhage
      1. Mobile, echogenic signals in vitreous, moving with eye motion
      2. Causes
        1. Eye Trauma
        2. Retinal or Vitreous Detachment
        3. Central vein Occlusion
        4. Subarachnoid Hemorrhage (occurs in 10-40% of SAH, poor prognostic sign)
    2. Retinal Detachment
      1. Appears as thick hyperechoic (bright white) curvilinear band
      2. Detachment protrudes, free-floating into the vitreous chamber
      3. Band of Detached Retina will be anchored to its posterior attachment at the optic disc
      4. Bedside Ultrasound in ED has high accuracy with training (Test Sensitivity 91%, Test Specificity 96%)
        1. Jacobsen (2016) West J Emerg Med 17(2): 196-200 +PMID: 26973752 [PubMed]
    3. Vitreous Detachment
      1. Swirling appearance with eye movement
      2. Similar to Retinal Detachment, but:
        1. Vitreous Detachment appears thinner and less intensely white
        2. Vitreous Detachment is not anchored at optic disc
        3. Evaluate with both moderate and high gain
    4. Choroid detachment
      1. Thicker detachment than Retinal Detachment
      2. Anchored at optic disc (as with Retinal Detachment)
      3. Does not move with eye motion (unlike Retinal and Vitreous Detachment)
  5. External pathology
    1. Optic Nerve Sheath Diameter increase (Increased Intracranial Pressure)
    2. Retrobulbar Hematoma
      1. Avoid any pressure on globe (risk of increased IOP)
      2. Stop Ultrasound immediately if identified and emergently consult ophthalmology

VI. Technique: Pupil Exam with Ultrasound

  1. Indications
    1. Patient unable to open their eye for pupil exam
  2. Transducer position
    1. Place transducer at inferior aspect of affected eye and directed in a coronal plane toward the eye brow
    2. Tilt the transducer until the iris and pupil are seen in cross section
    3. Pupil reaction will be evident by Ultrasound in this position
  3. Direct Light Reflex
    1. Pupil response observed on Ultrasound of eye when light is shined through the closed Eyelid on the ipsilateral side
  4. Consensual Light Reflex
    1. Pupil response observed on Ultrasound of eye when light is shined in the opposite eye

VII. Technique: Optic Nerve Sheath Diameter (ONSD)

  1. Indications
    1. Evaluation for Increased Intracranial Pressure
  2. Preparation
    1. Linear transducer held in transverse position (marker at 9:00)
  3. Measurement
    1. Measure a point 3 mm behind the Retina in the path of the Optic Nerve
    2. Measure width including the sheeth (two hyperechoic lines on either side of hypoechoic nerve)
    3. Obtain two nerve sheath diameters and average their measurements
  4. Interpretation
    1. Optic Nerve Sheath Diameter >5mm is consistent with Increased Intracranial Pressure
      1. Expect Optic Nerve sheeth <4 mm in infants and <4.5 mm in children <15 years old
  5. Resources
    1. Sonoguide Ocular Ultrasound
      1. http://www.sonoguide.com/smparts_ocular.html
  6. References
    1. Blaivas (2003) Acad Emerg Med 10(4):376-81 [PubMed]

VIII. Precautions

  1. Avoid any pressure to the eye if Globe Rupture is suspected (risk of vitreous loss)

IX. References

  1. Frasure (2014) Crit Dec Emerg Med 28(8): 2-9
  2. Laudenbach (2016) Ocular Ultrasound,Stabroom.com online video, accessed 4/1/2016
  3. Noble (2011) Manual Emergency and Critical CareUltrasound, Cambridge University Press, p. 203-11
  4. Reardon (2011) Pocket Atlas of Emergency Ultrasound, McGraw-Hill, p. 259-69
  5. Probst (2020) JAMA Netw Open 3(2):e1921460 [PubMed]

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