Dr. Andrew Shannon, MD, MPH of University of Florida College of Medicine – Jacksonville presents on Ocular Point-of-Care Ultrasound (POCUS) (07/20/2016)
Lecture Notes
Importance of Ocular POCUS
- Up to 67% of periorbital fractures have associated ocular trauma
- Periorbital swelling may prevent traditional exam
Eye Anatomy
- Medial area includes ducts that may require stents if violated in trauma
- Temporal region of internal anatomy includes optic disk and nerve; nasal includes fovea and macula
- Possible to evaluate for pupil diameter in axial cut under ultrasound
- Retina usually not visible on U/S
- Optic nerve sheath is visible on ultrasound, not the optic nerve
Equipment
- Amount of energy required for temperature change in the retina is much less than that required to make a change at other tissue
- Avoid over-exposing
- Apply tegaderm as barrier prior to exam
Retinal Detachment
- Complaint of
- “blurry vision”
- “wavy” visual loss
- curtain comes down/across vision
- Retina has blood supply from choroid
- As fluid accumulates between choroid/retina → retinal ischemia
- Retina is tethered to the choroid at the Ora Serrata and at the optic nerve
- If you see a detachment that does not respect the optic nerve, consider vitreous detachment instead of retinal detachment
- Worried about these in setting of trauma
- May be obscured by vitreous hemorrhage
- Retina will be hyperechoic and undulating
- May have vitreous hemorrhage + retinal detachment; can be detected on POCUS
Vitreous Hemorrhage
- Sudden, painless, floaters, dark spots, flashes
- 2/2: Trauma vs DM vs sickle cell
- POCUS: Hyperechoic, clotted blood
- Looks like clothes in a washer
- Terson’s Syndrome
- Vitreous hemorrhage associated with ICH (SAH)
- Occurs in 13% of patients with SAH
- Posterior Vitreous Detachment
- May also appear as hyperechoic linear density “lifted off” posterior globe
- Thinner, smoother, darker than retinal detachment
- Crosses optic nerve (unlike RD)
Orbital Wall fracture
- May present as diplopia and blurry vision
- Herniation of inferior rectus
Retrobulbar Hematoma
- Compartment syndrome of the eye
- 90-120 min of ischemia → irreversible vision loss
- Tx: Timolol, pilocarpine, acetazolamide
- May require lateral canthotomy
- Indications: APD, loss of vision, IOP >40 mmHg
Penetrating Injury/Globe Rupture
- May note extruded uveal tissue (almost always brown)
- Irregular pupil will point toward area of injury
- Pt NPO
- Abx: Cephalosporin or anti-penicillinase PCN (i.e. augmentin)
- Update tetanus
- Anti-emetic
- Shield eye & minimize manipulations
- Modified Seidel Test
- Use fluoroscein and cobalt blue filter to note aqueous humor flow
- Hyphema may be noted
- Ultrasound
- Avoid if unnecessary and use gingerly
- Findings
- ↓ in globe size
- AC collapse
- Buckling of sclera
- Anterior Chamber Decompression
- From trauma or eroding corneal ulcer
- Foreign Body
- May see in 30% of open globe
Lens Dislocation/Subluxation
- Edge of lens may be visible in/through pupil
- Complete dislocation/luxation: Lens displaces into vitreous or rarely into AC
- Differential dx for monocular diplopia: lens dislocation vs psych
- Dislocation
- Posterior more often than anterior
- Typically s/p replacement (cataracts surgery); may see in Marfan’s and trauma
- Avoid dilating pupil
Optic Nerve Sheath Measurement
- ONS is contiguous with dura mater
- Papilledema is delayed in comparison to optic nerve sheath diameter change
- Normal ONS is up to 5.0 mm diameter
- Measure 3 mm posterior to globe for both eyes
- Take average 2 or more readings
- Average ONSD > 5.2 mm is considered abnormal
- Consider ↑ ICP
- If ONS <5 mm, unlikely ICP >20 mmHg
- If >5.8, suspect ↑ ICP
- Crescent sign: Optic nerve protrudes into the globe
- Drusen: Optic nerve head drusen; may falsely appear as a FB
EM Rounds 