To describe the clinical manifestations and magnetic resonance imaging (MRI) characteristics of idiopathic optic perineuritis patients in Korea.

A retrospective chart review of 5 patients (6 eyes) with idiopathic optic perineuritis and 7 patients (7 eyes) with optic neuritis was performed.

The mean age of the 5 patients with idiopathic optic perineuritis was 59 years, and the mean age of the 7 patients with optic neuritis was 31.1 years. A relative afferent papillary defect (RAPD) was present in 4 eyes with idiopathic optic perineuritis, and in all 7 eyes with optic neuritis. All six eyes with idiopathic optic perineuritis showed relatively severe optic disc swelling, and 6 eyes with optic neuritis showed mild optic disc swelling. MRI demonstrated optic nerve sheath enhancement in all patients with idiopathic optic perineuritis and optic nerve enhancement in six patients with optic neuritis.

On MRI, compared with optic neuritis, idiopathic optic perineuritis had a higher onset age, relatively severe optic disc swelling, and optic nerve sheath enhancement. Because idiopathic optic perineuritis is known to have different treatment strategies and prognosis compared with optic neuritis, differential diagnosis is crucial. The clinical manifestations and MRI characteristics of idiopathic optic perineuritis in the present study will help in the diagnosis of Korean patients.