An Eye Test
5 year old boy suffers a traumatic orbital injury.
Publication Date: 2009-05-21
5 year old male who sustained large lacerations to the right forehead, right upper brow and right lid after a plate glass mirror fell on him. He had additional lacerations to the torso and extremities. CT scan of the orbits was done to evaluate for fracture and retained foreign bodies. An adequate ophthalmologic exam could not be performed in the emergency department.
Axial and sagital nocontrast CT through the level of the orbits demonstrate asymmetric enlargement of the right anterior chamber with posterior displacement of the right lens. The right anterior chamber measures 6 mm compared to 3 mm on the left. There is subtle irregularity of the lateral margin of the right globe without gross disruption of the wall. The images did not show post-septal hemorrhage. No foreign bodies were seen.
The familiar CT findings of a lacerated globe are a small, irregular globe that contains blood or air. The CT observation of an enlarged anterior chamber as a finding in rupture of the posterior sclera is an additional finding. Rupture of the globe is an ophthalmologic emergency. Prompt diagnosis and treatment are imperative to prevent further injury to the eye.
Traumatic rupture of the posterior sclera may decompress the vitreous and allow retropulsion of the lens (the lens sinks backward slightly) resulting in incomplete dislocation. Incomplete dislocation of the lens, or subluxation, is common, as some of the suspensory zonules usually remain intact. Subluxation of the lens may deepen the anterior chamber, but the lens is tilted or rotated. The resulting “deepening” of the globe’s anterior chamber is a well-known clinical sign of scleral rupture.
The depth of the normal anterior chamber ranges from about 2.5 to 3.5 mm; the depth varies with the method of measurement, age, and sex. On CT, the anterior and posterior chambers appear as a single fluid-filled compartment. “Indirect” rupture of the sclera involves sclera remote from the site of impact. A small rupture of the posterior sclera may permit vitreous to prolapse through the defect. With decompression of the vitreous, the lens sinks backward slightly, though the normal attachments of the lens, the suspensory ligaments or ciliary zonules, remain intact. This retropulsion of the lens enlarges or deepens the anterior chamber.
A complete traumatic posterior dislocation of the lens would cause the lens to sink to the dependent aspect of the vitreous. Narrow angle glaucoma typically demonstrates a small anterior chamber. Some congenital and syndromic glaucomas can present with an enlarged anterior chamber, but would not be consistent with this patient's history.
Blood in the anterior chamber (hyphema) often prevents identification of a deep anterior chamber at slit-lamp examination. In addition, a ruptured globe occasionally will have normal intraocular pressure and normal visual acuity, though more often vision in the affected eye is limited to light perception (or worse). It can be difficult to obtain an adequate ocular exam, especially in children, and a CT exam can help determine the status of the globe and for the evaluation of post-septal structures and hemorrhage.
- Weissman JL et al. Enlarged Anterior Chamber: CT Finding of a Ruptured Globe AJNR 16:936–938, Apr 1995 Chaudhary AK, Jha B. Imaging Findings of Congenital Glaucoma in Opitz Syndrome. AJNR 29:1003-05, May 2008