B-scan Ultrasound Patterns: RD, PVD, Choroidal Detachment and Masses
Last updated: October 2026
When the fundus is hidden by cataract, blood or corneal opacity, B-scan answers three questions: is the retina attached, is there a mass, and is there a foreign body? Always scan dynamically (ask the patient to move the eye) and compare with the fellow eye.
Membranes in the vitreous cavity
| Feature | Posterior vitreous detachment | Retinal detachment | Choroidal detachment |
|---|---|---|---|
| Shape | Thin, smooth, often incomplete | Folded or funnel-shaped (open or closed funnel) | Smooth, thick, dome-shaped; "kissing" if large |
| Attachment | May attach at the disc or vitreous base, but often free | Attached at the optic disc and the ora serrata | Does not reach the disc; anchored by vortex veins |
| Reflectivity (A-scan) | Low (spike well under 100%) | High (100% spike at high gain and at low gain) | High, often a double-peaked spike |
| Movement after eye movement | Marked, undulating, with long after-movement | Moderate (less in chronic RD or PVR) | Little or none |
| Under the membrane | Clear or with blood | Clear or with cells or blood | Clear (serous) or echogenic (haemorrhagic) |
Masses
| Lesion | B-scan shape | A-scan internal reflectivity | Other clues |
|---|---|---|---|
| Choroidal melanoma | Dome or "collar-stud" (mushroom) shape | Low to medium, regular, with decreasing spikes ("angle kappa") | Acoustic hollowness, choroidal excavation, orbital shadowing; internal vascular pulsation |
| Choroidal haemangioma | Smooth dome, usually posterior pole | High | No excavation; orange lesion clinically |
| Metastasis | Flat or lumpy, often multifocal | Medium to high, irregular | History of cancer (breast, lung) |
| Disciform scar or haemorrhage | Irregular, flat to elevated | High, irregular | Fellow-eye AMD; changes over weeks |
| Retinoblastoma | Irregular mass | High | Calcification with dense shadowing (persists at low gain) |
| Optic disc drusen | Bright nodule at the disc | Very high | Persists at low gain, with posterior shadowing |
Other common findings
- Vitreous haemorrhage: low-reflective dots that move freely. Fresh blood is faint; older blood organises into membranes. In diabetes, look for traction on the retina; in a non-diabetic, look for a tear or detachment.
- Endophthalmitis: diffuse vitreous opacities and choroidal thickening; check for retinal detachment before tap and injection.
- Intraocular foreign body: very bright echo with shadowing; metal and glass show reverberation artefacts. CT is the test of choice; avoid MRI if a metallic foreign body is possible.
- Posterior scleritis: thickened sclera with fluid in Tenon's space, giving the "T-sign" around the optic nerve.
- Dislocated lens or IOL: bright, often mobile structure lying on the retina.
- Staphyloma: posterior outpouching of the globe in high myopia; affects biometry.
Technique tips: start at high gain to find faint membranes, then lower the gain to judge reflectivity. Scan in transverse and longitudinal planes, centre the probe on the lesion for height measurement, and document axial length if a vitrectomy or IOL is planned. In open-globe injury, do not press on the eye; scan through the closed lid with plenty of gel, or defer.
Related: retinal detachment, ocular tumours, COMS findings, open globe injury and drusen vs papilloedema.
Key sources
- Byrne SF, Green RL. Ultrasound of the Eye and Orbit. 2nd ed. Mosby; 2002
- AAO BCSC Section 12: Retina and Vitreous and Section 4: Ophthalmic Pathology and Intraocular Tumors (current editions)
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