Seven Rings of Trauma
The 'Seven Rings of Trauma' are seven distinct, circumferentially-oriented ocular tissues anterior to the equator which are classically damaged following a closed globe blunt injury. This damage occurs because fluids within the eye cannot be compressed, and are thus forced to expand, causing disruption of normal ocular architecture. More specifically, the lens-iris diaphragm is forced posteriorly and, owing to their attachments to the scleral wall, can result in splitting or detachment at the root.
- Sphincter pupillae - The sphincter pupillae is the involuntary muscle responsible for pupillary constriction mediated by parasympathetic nervous system. This muscle encircles the pupillary margin of the iris and is 0.75mm wide. Radial sphincter tears at the pupillary margin can be appreciated with slit lamp biomicroscopy and may be associated with distortion of the pupil, diminished response to light, or traumatic mydriasis.
- Iris base - The iris base is the root of the iris attached to the scleral wall. Blunt trauma can cause iridodialysis, or a separation between the iris root and the ciliary body. This often results in a D shaped pupil.
- Anterior ciliary body - Damage to the anterior ciliary body is characterized by angle recession (longitudinal tear of ciliary body face splitting circular fibers from longitudinal fibers of ciliary body). There is marked posterior displacement of the iris root and widened ciliary body band posterior to the scleral spur on gonioscopy. The proposed mechanism of recession is that blunt trauma forces aqueous humor laterally and posteriorly against the iris and angle, which exerts traction on the iris root leading to a tear between the longitudinal and circular muscles of the ciliary body. With enough force, the ciliary arteries can be broken, leading to a hyphema. This initial insult may damage the trabecular meshwork and Schlemm’s canal leading to an early IOP spike. However, long term scarring and fibrosis of the trabecular meshwork/Schlemm’s canal can lead to elevated pressure years down the road. Glaucoma is not due to recession per se but due to this collateral damage to the trabecular meshwork. Of note, this is the most common finding after globe contusion, and can be seen on gonioscopy years after the inciting trauma.
- Separation of ciliary body muscle fiber attachment to the scleral spur - Separation of the ciliary body muscle from the scleral wall results in a cyclodialysis cleft, exposing the internal scleral wall to the anterior chamber. Hypotony is a common early complication due to the free passage of aqueous from the anterior chamber into the suprachoroidal space, which can result in findings such as hypotony maculopathy. However, ocular hypertension may be a long-term sequelae if the cyclodialysis cleft closes with resistance to aqueous outflow.
- Trabecular meshwork - Trabecular meshwork can be damaged directly, resulting in a trabecular meshwork tear or flap at the point of rupture.
- Zonules - Damage to the zonules can result in zonular dialysis. Depending on the extend of zonular damage, the crystalline lens may be stable, may have evidence of phacodonesis, or may subluxate or dislocate.
- Retinal attachment at the ora serrata - The retinal attachment to the ora serrata can be damaged by blunt globe trauma. Retinal dialysis can occur, which is defined as a disinsertion of the retina at the ora serrata. After trauma, most commonly the inferotemporal quadrant is involved but superonasal dialysis is pathognomonic of trauma. This is due to the fact that bilateral inferotemporal dialysis of young age is a known entity which is non-traumatic. Other findings can include vitreous base avulsion, which reveals a classic 'bucket handle' finding, and may be associated with retinal dialysis, retinal tears, or vitreous hemorrhage.
Blunt closed globe injury is a common entity. The most common pediatric eye injuries are sports-related trauma, wooden stick injury, and thermal burns due to firecrackers. The other common modes of injury can be assault, workplace trauma, road traffic accidents, self-fall, and nonaccidental injuries. These injuries are more common in adults. Closed globe injuries can also be accidental and are broadly listed as occupational and occupational. The occupational injuries can be due to high-risk occupations like the manufacturing industry, plumbing, mining, and agriculture. Nonoccupational can be sports trauma and domestic violence.
Damage to the seven rings of trauma is caused by closed globe injury. Four phases of deformation of globe following ocular trauma by a projectile has been described. The phases are compression, decompression, overshoot and oscillation. Due to decrease in anterior posterior diameter of the globe and increase in the equatorial diameter, the circumferential tissues of eye which are arranged like rings are stretched and damaged by blunt closed globe ocular trauma.
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