Traumatic chiasmopathy following mild trauma in a patient with thyroid orbitopathy

Purpose: Traumatic injury to the optic chiasm is rare and most frequently caused by high-velocity head trauma. It classically results in bitemporal hemianopsia and often presents in conjunction with multiple other traumatic injuries, such as skull fractures and cerebrospinal fluid leaks. We present the case of a 40-year-old woman with pre-existing thyroid orbitopathy who struck her forehead after a fall from standing height. Observations: This patient suffered immediate profound unilateral vision loss from traumatic optic neuropathy and possible optic nerve avulsion. The fellow eye manifested a temporal hemianopsia with delayed retinal nerve fiber layer and nasal hemimacular ganglion cell layer thinning on optical coherence tomography, consistent with chiasmal pathology. Magnetic resonance imaging showed no definitive lesions at the optic chiasm or more posteriorly along the afferent visual pathway. Conclusions and importance: This patient's severe vision loss suggests that proptosis from thyroid orbitopathy can sensitize the anterior visual pathway to trauma. In this case, we propose that the lack of laxity in the intra-orbital optic nerves allowed transmission of stretching forces to the optic chiasm in the setting of low-velocity blunt trauma.