Seven rings of trauma
Seven rings of trauma are circumferentially oriented ocular tissues anterior to the equator which are classically damaged following a closed globe 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 tear 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.
- The iris base - causing "iridodialysis," or a separation between the iris root and the ciliary body. This is often described as a D shaped pupil.
- Anterior ciliary body trauma 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. Glaucoma is not due to recession per se but due to collateral damage to trabecular meshwork. Of note, this is the most common finding after contusion, and can be seen on gonioscopy years after the inciting trauma.
- Seperation of ciliary body muscle fiber attachment to the scleral spur - resulting in cyclodialysis cleft, exposing the internal scleral wall. Hypotony is a common early complication due to the free passage of aqueous from the anterior chamber to the suprachoroidal space. However, ocular hypertension may be a long-term sequelae if the cyclodialysis cleft closes with resistance to aqueous outflow.
- Trabecular meshwork - resulting in a trabecular meshwork tear or flap at the point of rupture.
- Zonules - zonular dialysis resulting in subluxation or dislocation of the crystalline lens.
- Retinal attachment at ora serrata - Retinal dialysis is defined by 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 is a known entity which is non-traumatic.
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 diamter the circumferential tissues of eye which are arranged like rings are stretched and damaged by oular trauma
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