Eye Ultrasound Notes

Anatomy of the Eye

• Lens: Focuses light entering the eye, working with the cornea to allow clear vision.

• Pupil: Expands in dim light and shrinks in bright light.

• Optic Nerve: Connects the retina to the brain.

• Retina: Transforms light into signals sent to the brain, located at the back of the eye.

Eye Structure

• Cornea: Covers the iris, anterior chamber, and pupil.

• Iris: Contains anterior and posterior chambers.

  • Anterior Section: Superficial to the iris.

  • Posterior Section: Deep to the iris.

• Key Ultrasound Finding: Ensuring the retina is attached to the optic disc.

Scanning the Eye

• Patient lies in supine position with eyes closed.

• Transducers: Linear (7-10 MHz) or phased array (1-5 MHz).

• Pillow support under shoulders for ergonomics.

• Apply sterile gel on the eyelid with a transducer cover; avoid excess pressure.

• Patient looks up and down slowly to rule out hemorrhage and assess for retinal detachment.

Ultrasound Technique

• Patient looks up/down, left/right (label these movements).

• Aseptic technique is crucial.

• Use a high-gain technique to differentiate pathology (label high gain); this helps in showing dense vitreous hemorrhage and floaters.

• Examine the anterior chamber with a small footprint, focusing on the iris for better definition. The patient looks up or down for a coronal view.

Ultrasound Appearance of the Eye

• The eye is divided into anterior and posterior sections.

  • Anterior Section: Superficial to the iris.

  • Posterior Section: Deep to the iris.

• Key Ultrasound Finding: Ensuring the retina is attached to the optic disc.

• Comparison with the contralateral eye is important to rule out pathology.

• Visual representation of eye structures including the eyelid, cornea, anterior chamber,iris, lens, vitreous body, retina, optic nerve and sheath diameter with normal being <5mm

Indications for Ocular Ultrasound

• Decreased or loss of vision.

• Suspected foreign body.

• Ocular pain.

• Eye trauma.

• Head injury with suspected intracranial pressure.

• Follow-up melanoma after laser treatment.

• Degenerative disorders.

• Asymptomatic loss of vision.

• Contra-indication: Penetrating trauma (risk of infection).

Ultrasound Requests

• Ocular emergencies account for 3% of ED visits.

• Direct visualization of intraocular structures is difficult when eyelids are swollen due to trauma.

• Lens opacification and hyphaemia can block viewing of the posterior structure of the eye.

• Communication with the patient is crucial for understanding the injury.

• Evaluation of the eye and facial structures determines the appropriate management plan.

Anterior Chamber Pathologies

Hyphema

• Blood in the anterior chamber, usually caused by trauma; can indicate underlying pathology.

• Assess integrity of pupil and cornea.

• Ultrasound shows viscous fluid with low-level echoes, sometimes complex.

• Assess the size of the fluid and compare to the contralateral side.

Posterior Chamber Pathologies

Cataract

• Clinically, a white reflection and opaque lens.

• Related to age, congenital issues, trauma, or infection.

• Ultrasound is needed to assess structures that are not visible with a microscope.

• Ultrasound Appearance:

  • Small echogenic dot in the center of the lens or a dense echogenic area within the lens.

  • Can mimic a foreign body.

Vitreous Hemorrhage

• Blood leaks or pools in the vitreous humor.

• Causes:

  • Rupture of normal vessels from trauma, retinal detachment or tear, posterior vitreous detachment.

  • Pathological rupture from diabetic retinopathy or ocular malignancy.

Symptoms

• Floaters (unilateral) and some vision loss.

• Important to know patient history to determine cause.

• "Swirling" motion at posterior segment when the patient moves their eye left to right.

Ultrasound Appearance

• Acute: Ill-defined, scattered collections of echogenic foci (increase gain to visualize).

• Mobile when the eye is moved side to side.

• Subacute/Chronic: Echogenic foci are more membranous and organized.

• The entire vitreous body can appear as an echogenic hematoma.

• Mobility declines with age of hemorrhage.

Retinal Detachment (RD)

• Retinal detachment occurs when vitreous liquid pours through tears in the retinal layer.

• Ultrasound Appearance:

  • Acute Phase: Thin to mildly thickened membrane anchored by the optic disc.

  • Chronic Phase: Thickened membrane with reduced or absent colour Doppler flow.

  • Membrane flutters with eye movement (confirms RD); perfusion can still be present under color Doppler.

• Do not confuse with lens and vitreous detachment.

Symptoms

• Can be asymptomatic if only a small part is detached.

• Floaters.

• Flashes of light.

• A dark shadow or “curtain” on sides or middle of vision.

Ultrasound Appearance

• Bright, continuous, smooth, and folded membrane within the vitreous fluid.

• Reflective and moves freely.

• If total or extensive, the detached retina has a triangle shape with insertion into the optic disc.

• The retina still has flow on color Doppler.

• The retina never detaches at the site of the optic nerve.

Posterior Vitreous Detachment

• Occurs more in older patients.

• In young patients, the vitreous is adherent to the internal lining of the retina.

• As a person ages, the gel-like consistency degenerates, leading to collapse of the vitreous.

• Produces thick bundles of collagen fibrils that float in the vitreous ("floaters").

• Degeneration also causes weakening of the adhesion of the vitreous to the retina, resulting in posterior vitreous detachment.

• Can be spontaneous or a result of cataract surgery, trauma.

Ultrasound Appearance

• Linear, echogenic membrane in the posterior compartment.

• Freely mobile.

• Membrane crosses the intersection of the optic nerve sheath and the posterior wall of the globe (does not occur with retinal detachment).

• If acute stage, will see “after movements” more prominent than choroid or retinal detachments.

Choroid Detachment

• Detachment of the choroid from the sclera due to accumulation of fluid in the suprachoroidal space.

• Often due to an increase in intraocular pressure.

• Can be serous (fluid-filled) or hemorrhagic (blood-filled).

Main Causes

• Trauma

• Surgery

• Spontaneous

• Medications to lower IOP

• Neoplasms

Ultrasound Appearance

• Paired echogenic bands extending posteriorly from the ciliary bodies.

• These bands remain fixed in position during movement of the eye (differentiates from retinal and posterior vitreous attachments).

Foreign Body (FB) and Trauma

• Trauma is the most common indication for ultrasound of the eye, followed by foreign body.

• Trauma can be present with or without pain, sometimes also associated with loss of vision or irritated eye.

• If global rupture is suspected, avoid performing an ultrasound as this can cause extra pressure.

• Global rupture will show collapse of the anterior chamber with extrusion of vitreous fluid.

• It is important to rule out foreign bodies, as undiagnosed FB can cause permanent loss of vision in the future.

• Depending on the type of FB, it can be echogenic with shadowing if glass or metal is present; hyperechoic if wood FB.

• FB detection has greater sensitivity with comparison to CT scans and is not suitable for MRI if metal is suspected.

• Assess the vitreous component, as a hemorrhage can sometimes be present depending on the severity of the puncture.

Symptoms

• Tearing

• Decreased visual acuity

• Photophobia

• Feeling of sensation of a FB

Ultrasound Appearance

• Abnormal echogenic structure with posterior acoustic shadowing.

• Can sometimes see a twinkling artifact or reverberation artifact.

• Often there is a vitreous hemorrhage.

• Can be location-dependent with mobility, especially with a vitreous FB.

• With FB and trauma, globe rupture, retinal detachment, or choroidal detachment can also occur.

Case Studies

Case 1: Disc Drusen

• 9-year-old boy

• What is disc drusen? A build-up of calcium and protein within the optic nerve.

• Can be hereditary; also exists in patients with age-related macular degeneration.

• Often seen by ophthalmologists looking in the back of the eye on a routine exam.

• Do not usually affect vision but if so can have peripheral vision issues.

• Ultrasound: Echogenic focus within or on the surface of the optic nerve head; can get posterior shadowing if lesions are large enough.

Radiologist Report

• There are echogenic foci within the posterior retina measuring 2.3 mm on the right side and 3.6mm on the left side which are most typical of drusen.

Case 2: Mature Cataract

• Ultrasound right eye

• Mature Cataract: Assess for retinal detachment

Radiologist Report

• The retina appears smooth and uniform in thickness. No abnormal echogenicity is seen within the vitreous humor. The optic nerve disc appears unremarkable. There is increased echogenicity of the lens consistent with a cataract. No evidence of retinal detachment is seen.