Ocular / ophthalmic — Reference values

Ocular / ophthalmic — Reference values: Safe technique — scan through the eyelid, Minimum sweep to learn anatomy, Optic nerve sheath — adult, Optic nerve sheath — child.

Use a no-pressure technique, abundant gel and an ocular preset when available. If open globe is suspected, do not compress the eye and prioritize ophthalmology or emergency care; this section is teaching support and does not replace ophthalmologic examination.

Measurements and reference values

Measurement	Usual value	Note
Safe technique — scan through the eyelid	abundant gel, linear probe, no direct pressure, ocular preset	The probe should float on the gel. In trauma, severe pain or suspected perforation, the priority is not to compress the globe.safe: no pressure + ocular presettechnical limitation: no ocular preset or poor windowdo not compress: suspected open globeSource: StatPearls Ocular Ultrasound / ACEP Sonoguide
Minimum sweep to learn anatomy	transverse and longitudinal planes, resting eye and gentle eye movements	Identify the lens, vitreous, retina, posterior wall, optic nerve and retrobulbar space before searching for disease.Source: University of Iowa EyeRounds / EyeWiki
Optic nerve sheath — adult	≤ 5,0 mm	Measure 3 mm behind the retina/posterior globe wall; ideally measure both eyes and interpret with the neurologic context.consensus normal: ≤5,0 mmborderline or divergent: >5,0–5,7 mmhigh risk for raised intracranial pressure: ≥5,8 mmSource: ACEP Sonoguide / StatPearls / revisão de bainha do nervo óptico
Optic nerve sheath — child	≤4.5 in 1–15 years; ≤4.0 under 1 year mm	Pediatric thresholds vary; use as screening, not as a standalone diagnosis of raised intracranial pressure.consensus normal: ≤4.5 mm child; ≤4.0 mm infantborderline: up to ~0.5 mm above cutofflikely abnormal: clearly above cutoff + clinical contextSource: ACEP Sonoguide / revisão de bainha do nervo óptico
Optic disc elevation	≤ 0,6 mm	Elevation above 0.6 mm favors papilledema in the right context; optic disc drusen can mimic pseudopapilledema.no relevant elevation: <0,4 mmgray zone: 0,4–0,6 mmsuspicious for papilledema: >0,6 mmSource: StatPearls Ocular Ultrasound / estudos de papiledema
Adult ocular axial length	~22–24,5 mm	Varies with refraction, population and method. Very long values suggest axial myopia; short values may occur in hyperopia or small eyes.usual adult range: 22–24,5 mmoutside mean, correlate refraction: 20,5–21,9 ou 24,6–26,4 mmmarkedly outside range: <20,5 ou ≥26,5 mmSource: EyeWiki / Scientific Reports axial length
Normal posterior segment	anechoic vitreous; thin continuous retina on posterior wall; optic disc as reference	Dynamic eye movement helps separate true membranes from mobile vitreous echoes.Source: StatPearls / ACEP Sonoguide / EyeWiki
Intraocular mass — required measurements	base, height, location, reflectivity, shadowing and vascularity when indicated	Solid mass, growth, calcification in a child or associated detachment requires specialist ophthalmologic evaluation.no mass: regular wallindeterminate lesion: document and comparehigh risk: solid vascular mass, calcified lesion in a child, or growthSource: EyeWiki / revisão de ultrassonografia oftalmológica

Classifications and calculators

Interactive assistant — ocular ultrasound

Output	Color	Reading
Likely normal	Green	No warning sign, measurements within range and posterior segment without pathologic membranes.
Caution / indeterminate	Yellow	Borderline measurement, mobile vitreous echoes, posterior vitreous detachment, limited technique or trauma indication without open-globe signs.
Urgent	Red	Suspected open globe, retinal detachment, foreign body, absent central retinal artery flow, retrobulbar hematoma, lens dislocation or likely raised intracranial pressure.

The Clear button resets the calculation. The output is a teaching triage to standardize reasoning and communication; ocular emergencies still require specialist evaluation.

Source: StatPearls / ACEP Sonoguide / EyeWiki

Anatomic map for patients and learners

Structure	How it appears	Why it matters
Lens	Biconvex structure just behind the iris; normally centered.	Subluxation or dislocation may occur in trauma and affect vision.
Vitreous	Dark/anechoic content filling most of the eye.	Mobile echoes suggest blood, inflammation or vitreous degeneration.
Retina	Thin line along the posterior wall; when detached, it becomes a thicker membrane tethered to the optic disc.	Retinal detachment is an emergency, especially if the macula is still attached.
Choroid	Deep vascular layer; detachments are often convex and do not cross the optic disc.	Helps differentiate choroidal detachment from retinal detachment.
Optic nerve and its sheath	Dark structure behind the globe; the sheath is measured 3 mm behind the posterior wall.	Enlargement may accompany raised intracranial pressure.
Central retinal artery	Doppler flow within the optic nerve entering the eye.	Absent or markedly reduced flow in the right context suggests arterial occlusion.

Source: EyeWiki / StatPearls / ACEP Sonoguide

Safe technique step by step

Step	Do	Avoid
Before touching	Ask about penetrating trauma, recent surgery, severe pain or globe deformity.	Pressure if open globe is suspected.
Prepare	Thick gel layer over the closed eyelid and linear probe.	Dry contact or compression to “improve” the image.
Set up	Ocular preset/low mechanical and thermal indices when available.	Unnecessary high output.
Sweep	Horizontal and vertical planes, with gentle eye movements to assess mobility.	Concluding without quadrant assessment or dynamic motion.
Measure	Optic nerve sheath 3 mm behind the retina; axial length along the visual axis when indicated.	Oblique measurement or off-axis image.

Source: ACEP Sonoguide / University of Iowa EyeRounds / StatPearls

Retina, vitreous and choroid — how to differentiate

Finding	Ultrasound clue	Suggested action
Normal posterior segment	Dark vitreous, no membrane; retina attached to wall.	Correlate with clinical examination.
Vitreous hemorrhage	Heterogeneous mobile echoes, more evident with high gain and eye movement.	Assess hidden retina; guide ophthalmology according to context.
Posterior vitreous detachment	Thin very mobile membrane, not tethered to the optic disc and may cross the midline.	Differentiate from retina; urgent return if flashes, dark curtain or worsening.
Retinal detachment	Thicker membrane, tethered to the optic disc, often V-shaped or funnel-shaped.	Urgent ophthalmologic evaluation; macula-on is more time-sensitive.
Choroidal detachment	Thick convex membranes, may appear “kissing”, spare the optic disc.	Correlate trauma, surgery, hypotony or inflammation; specialist evaluation.

Source: ACEP Sonoguide / StatPearls / EyeWiki

Emergencies and warnings in ocular ultrasound

Situation	Useful findings	Practical message
Open globe / globe rupture	Irregular contour, abnormal anterior chamber, extruded contents; foreign body may be present.	Do not compress. Stop scanning if suspicion is high.
Intraocular foreign body	Very echogenic focus with shadowing or reverberation.	Treat as penetrating trauma until proven otherwise.
Lens dislocation	Lens displaced into vitreous or anterior chamber, outside the expected axis.	Associate with trauma, connective-tissue disorder or surgery.
Retrobulbar hematoma	Collection behind the globe, proptosis; globe may look “pointed”.	Orbital emergency if pain, proptosis or vision loss is present.
Central retinal artery occlusion	Absent or markedly reduced flow; sometimes an echogenic embolic focus near the disc.	Short therapeutic window; immediate communication.
Orbital cellulitis / abscess	Soft-tissue thickening, collection, restricted motion, pain.	Ultrasound helps, but computed tomography/ophthalmology may be needed.

Source: ACEP Sonoguide / StatPearls

Optic nerve sheath and papilledema — color reading

Measurement	Green	Yellow	Red
Adult	≤5,0 mm	>5,0–5,7 mm	≥5,8 mm
Child 1–15 years	≤4,5 mm	4,6–5,0 mm	>5,0 mm + clínica
Under 1 year	≤4,0 mm	4,1–4,5 mm	>4,5 mm + clínica
Optic disc elevation	<0,4 mm	0,4–0,6 mm	>0,6 mm

These cutoffs do not replace neurologic evaluation. Hydration, hypercapnia, technique, image axis and ocular disease may change the measurement.

Source: ACEP Sonoguide / StatPearls / revisão de bainha do nervo óptico

Biometry and masses — what to document

Use	Document	Watch for
Ocular biometry	Axial length, method, right/left eye and measurement quality.	Inter-eye difference and refraction.
Opaque media	Dense cataract, hemorrhage or opacity blocking fundoscopy.	Ultrasound assesses the hidden retina but does not replace complete examination.
Melanocytic or solid mass	Base, height, shape, reflectivity, shadowing, subretinal fluid and vascularity.	Growth or activity signs require a specialist.
Child with mass/calcification	Echogenic intraocular mass, calcification or associated detachment.	Consider retinoblastoma until proven otherwise.

Source: EyeWiki / Ophthalmologic ultrasound reviews

Teaching checklist for the ocular report

Item	Question the report should answer
Safety/technique	Was it transpalpebral, no pressure, with limitation from pain/trauma?
Globe	Are contour, volume and anterior chamber preserved?
Lens	Is it centered or is there subluxation/dislocation?
Vitreous	Is it anechoic or are there mobile echoes compatible with blood/inflammation?
Retina/choroid	Is there a membrane? Is it tethered to the optic disc or does it spare the disc?
Optic nerve	Were sheath and disc measured when there was a neurologic indication?
Doppler	Was central retinal artery flow assessed when acute vision loss was present?
Conclusion	Does the conclusion separate normal, indeterminate and urgent, with an objective recommendation?

Source: StatPearls / ACEP Sonoguide / EyeWiki

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