Unilateral Idiopathic Optic Perineuritis in a Normal Fundus

Abstract

A 22-year-old woman of Malay ethnicity presented with severe blurred vision in the right eye and experienced periocular pain with eye movement. She had a visual field defect over the affected eye, while an examination showed clinically normal optic discs. Relative afferent pupillary defect was also present in the right eye, with reduced optic nerve function. Optic nerve imaging revealed the ‘doughnut sign’ and ‘tram track’ signs, which are characteristics of optic perineuritis. The patient was initiated on a steroid regime that was tapered off over four months. Her visual function recovered gradually during the treatment until reaching a satisfactory final visual outcome. This is a unique case where optic perineuritis occurred in a normal fundus and magnetic resonance imaging (MRI) served as an important diagnostic tool for the condition. Optic perineuritis (OPN) is an orbital inflammatory disease that involves the meningeal sheath surrounding the optic nerve.[1] It can be idiopathic or secondary to an underlying systemic autoimmune disorder.[1,2] Visual loss in OPN results from inflammation of the tissue surrounding the optic nerve, resulting in mechanical compression of the nerve and subsequent ischaemia.[1] OPN can be diagnosed using an optic nerve sheath biopsy, while magnetic resonance imaging (MRI) diagnoses OPN through perineural enhancement, making it a useful diagnostic tool.[2] Upon diagnosis, OPN should be treated with corticosteroids for a prolonged period to ensure visual recovery.[3] We report a unique case of unilateral OPN with severe visual loss in a young Malay woman with a normal fundoscopy who was successfully treated with prolonged corticosteroids.