Ophthalmic segment of internal carotid artery aneurysm mimicking normal tension glaucoma

A 41-year-old caucasian male was referred to the Glaucoma clinic at our tertiary referral centre with a diagnosis of normal tension glaucoma after the finding of increased bilateral asymmetrical cup/disc ratios, with normal intraocular pressures. On examination, the authors confirmed the presence of bilateral reduced optic disc rims alongside a left pale residual rim, and a further discovered a positive dyschromatopsia with a bilateral visual field alteration. The left visual field showed a relative scotoma confined to the vertical midline. After initiating investigation for suspected glaucoma, the authors ordered a magnetic resonance imaging that evidenced an internal carotid aneurysm along the ophthalmic segment, stretching across the optic chiasm with a major involvement of the left optic nerve and partial involvement of the right optic nerve. Aneurysm embolisation was performed with complete resolution of signs and symptoms achieved 5 months post-operatively. Despite glaucoma being the most frequent condition causing optic disc atrophy and visual field loss, it is not the only cause. Any atypical visual field defect not in keeping with a glaucomatous field loss should be further investigated. The ophthalmologist should thoroughly assess all signs that could lead to different diagnosis.