Blunt Trauma — Posterior Segment Signs

Commotio Retinae (Berlin's Edema)

Commotio retinae is the hallmark posterior-segment sign of blunt trauma: a transient grey-white opacification of the retina at the site of impact. Despite the name, it isn't true fluid accumulation — the underlying pathophysiology is mechanical disruption of the photoreceptor outer segments, caused by shock waves transmitted through the vitreous at the moment of impact. On optical coherence tomography, this shows up as hyperreflectivity and disruption of the ellipsoid zone (the photoreceptor inner segment/outer segment junction), which correlates directly with the mechanical injury seen on fundus exam.

When commotio retinae is centered on the macula rather than the periphery, it's specifically termed Berlin's edema — a historical name that, again, is a bit of a misnomer given the underlying photoreceptor disruption rather than true edema. The distinction between macular and peripheral involvement matters clinically: foveal involvement carries a substantially worse visual prognosis, since it's more likely to progress to photoreceptor apoptosis and permanent structural damage, whereas peripheral commotio retinae usually resolves without lasting visual sequelae. A rare but recognized late complication of severe macular commotio retinae is a full-thickness macular hole, arising from severe disruption of foveal photoreceptors and the overlying vitreoretinal interface.

Scleral Rupture

A severe enough blunt impact can rupture the sclera itself, not just the structures inside it. Scleral ruptures occur most commonly at the limbus and at the rectus muscle insertions — the sclera is thinnest just behind these muscle insertions, at roughly 0.3 mm, which makes that location the point of least resistance under blunt force. A ruptured globe from blunt trauma is managed the same way as any other open globe: a rigid shield, no pressure or manipulation, and emergent surgical repair (see the triage page for the full initial-management approach).

Retinal Tear Symptoms and the Tobacco Dust Sign

Flashes and floaters together are the classic warning symptoms of a new retinal tear following blunt trauma — flashes arise from vitreous traction on the retina, while floaters reflect debris or blood released into the vitreous cavity. Pain, double vision, and redness are much less specific for a retinal tear and shouldn't be relied on as the trigger for a dilated exam the way flashes and floaters should.

On exam, the "tobacco dust" sign (also called Schaffer's sign) — fine pigment cells suspended in the anterior vitreous — is a high-risk finding for retinal tear or detachment. These pigment cells are retinal pigment epithelium released through the tear itself, so their presence in the vitreous is essentially direct evidence that a break exists somewhere in the retina, even before it's been visualized on dilated fundus exam. Any patient with tobacco dust on slit lamp exam after trauma needs a thorough peripheral retinal exam to find and treat the tear before it progresses to a detachment.

Posterior Vitreous Detachment

Trauma can also precipitate an acute posterior vitreous detachment (PVD), where the vitreous separates from the retina. A Weiss ring — a circular piece of glial tissue that avulses from the optic disc margin during this separation — floating in the vitreous is a classic sign confirming that a PVD has occurred. A PVD isn't itself a retinal tear, but the traction it generates during separation is exactly the mechanism that can create one, which is why an acute, symptomatic PVD after trauma warrants the same flashes/floaters work-up as above.

Myopia as a Detachment Risk Factor

Patients with high myopia carry a substantially elevated risk of trauma-related retinal detachment compared to emmetropic or hyperopic patients. Myopic eyes are elongated along their axial length, and that elongation stretches and thins the peripheral retina — making it far more susceptible to tearing when the eye absorbs a blunt impact. This is worth asking about specifically in a trauma history: a myopic patient with flashes and floaters after blunt trauma should be treated with a higher index of suspicion for retinal tear or detachment than an equivalent non-myopic patient with the same symptoms.

Monocular Diplopia After Trauma

Double vision after trauma isn't always a muscle or cranial nerve problem. Monocular diplopia — double vision that persists even when the fellow eye is covered — points instead to an ocular problem within the affected eye itself, such as lens subluxation or corneal irregularity, rather than a brainstem injury or cranial nerve palsy. The single most useful bedside test is simply covering each eye in turn: if the diplopia persists with the uninjured eye covered, the source is in the eye that was covered — not centrally, and not from a nerve palsy. This makes it a quick, no-equipment way to redirect the work-up toward a lens or corneal cause of posterior- (or anterior-) segment origin rather than a neurologic one.

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