Introduction: The most common cause of chiasmopathy is compression of the optic chiasm by parasellar tumours. The tumours may produce any pattern of visual field defect depending on the tumour location and the patient’s chiasmal anatomy. Rare, non-compressive causes of chiasmopathy include, among others, infectious, post-infectious, inflammatory, autoimmune, demyelinating, toxic and ischaemic processes. Chiasmopathy can also occur due to trauma and radiation treatment. Case report: We report a case of a 43-year-old patient who was admitted to our department because of a two-month history of headaches and constant, symmetrical blurriness over the temporal sides of vision. After a wide-ranging diagnostic process, the patient was diagnosed with an isolated optic chiasmitis in the course of myelin oligodendrocyte glycoprotein-associated disease, which is a rare, monophasic or relapsing, antibody-mediated inflammatory demyelinating disorder of the central nervous system. Conclusions: It is crucial to remember that parasellar tumours are not the only cause of bitemporal hemianopsia. Patients with bitemporal hemianopsia, if there is no compressive lesion of the optic chiasm, should be investigated for optic chiasmitis. Optic chiasmitis is not a diagnosis in itself, but a sign of an underlying pathology, and during its evaluation should be treated as a variation of atypical optic neuritis. We hope that this ophthalmic manifestation of a rare neurological disease will make other clinicians aware of the utter importance of careful evaluation of visual disturbances.