Diagnostic dilemma in visual loss due to diabetic papillopathy masquerading as optic neuritis

Diabetic papillopathy (DP), a rare complication of diabetes mellitus, involves benign changes in the optic nerve head due to metabolic stress or immune dysfunction. This report describes a middle-aged male patient with type 2 diabetes mellitus for 1 year, presenting with painless, progressive blurring of vision in his right eye for 2 weeks. His best corrected visual acuity was 6/18 in the right eye and 6/6 in the left. Examination revealed a sluggish pupillary reaction, grade 1 relative afferent pupillary defect, optic disc hyperaemia, obscured margins and venous tortuosity in the right eye. He was treated for presumed optic neuritis (ON) with intravenous and oral corticosteroids. However, Vision worsened during the period of corticosteroid treatment. Although a temporal association was observed, a causal relationship between corticosteroid therapy and worsening of DP cannot be definitively established from a single case. Anti-neuromyelitis optica antibody was negative while anti-myelin oligodendrocyte antibody was weakly positive. MRI showed optic nerve thickening without demyelination or raised intracranial pressure. After being diagnosed with DP, corticosteroids were tapered and the treatment focus shifted to strict glycaemic control. Disc oedema can be the common feature in both with microvascular occlusion in DP and inflammation in ON as the underlying cause. This case emphasises the importance of distinguishing DP from other optic neuropathies, as their treatments are vastly different and diametrically opposite.