Optic neuropathy due to allergic fungal rhinosinusitis.

An uncommon case of allergic fungal rhinosinusitis presented to the ophthalmology outpatient department of our hospital with complaints of blurred vision in the right eye of a few days duration and vague complaints of pain around the eyes. The visual acuity on examination was grossly reduced in the right eye and normal in the left eye. Color vision was normal. Anterior segment examination including pupils was normal. Dilated fundus examination was normal except for temporal pallor in the right optic disc. Automated perimetry and magnetic resonance imaging (MRI) scan of brain and orbit were done. The imaging report showed a bilateral pansinusitis with pressure on the right optic nerve. Perimetry showed a superior field defect on the right side. ENT consultation and computed tomography (CT) with contrast helped to diagnose this as a case of allergic fungal rhinosinusitis. The patient was started on systemic steroids under the care of the ENT surgeon. After a few days, pre-operative assessment showed a gross improvement of visual acuity. Endoscopic sinus surgery was done to remove the polyps and thick mucus material. Histopathologic examination confirmed allergic fungal mucin. Days after surgery, the visual acuity improved further and repeat perimetry showed gross improvement in the visual field. Good history taking and a detailed ophthalmic examination, keeping in mind the probable causes of loss of vision of few days duration with no findings other than a decreased visual acuity and a suspicious disc, were key to the early diagnosis and investigation in this case. This helped in early referral and management of the case before permanent damage and irreversible visual loss occurred. The optic nerve is a cranial nerve which, once damaged permanently, will not regenerate. The amount of sinus involvement was extensive on both sides and invariably the left optic nerve would have been involved in a few days, if intervention was delayed.