A 56-year-old woman, diagnosed 11 years ago with primary MNO of the right eye (OD). On examination she presented unilateral proptosis with soft palpebral oedema, conjunctivo-scleral ingurgitation due to compromise of the orbital venous drainage, restriction of the OD translations and binocular diplopia in elevation, levo and dextroversions, isochoric and normoreactive pupils and intraocular pressure (IOP) of 16 mmHg in both eyes. Initial visual acuity (VA) was unity. On funduscopy (FO) the papilla of the OD appeared hyperemic and slightly raised. Imaging tests identified a lesion compatible with intraconal MNO which was confirmed by biopsy. Given the benignity and VA, observation was chosen, together with magnetic resonance imaging (MRI) and visual field (VF) every 6 months.

After 4 years of follow-up, an inferior peripheral scotoma appeared in OD, deterioration of VA and IOP elevation up to 24-25 mm Hg, which was controlled with topical beta-blocker and latanoprost. One year later, VA OD was 0.3, IOP 20 mm Hg (with treatment) and CV and FO had significantly worsened. Given the progression, treatment with RFE (total dose of 50 Gy in 30 fractions of 1.67 Gy) was decided, ending with VA OD of 0.1.

CV, FO and VA gradually recovered (VA OD of 1, 38 months after treatment); however, palpebral oedema, proptosis and ingurgitation are unchanged, binocular diplopia is stable and well tolerated and IOP is controlled with treatment.

