IntroductionBlastic plasmacytoid dendritic cell neoplasm (BPDCN), a rare haematological tumor arising from dendritic cells presents mainly as plaque-like cutaneous lesions but can also involve bone marrow, lymph nodes, central nervous system (CNS), and other tissues.Case descriptionIn this case report we have described an interesting case of BPDCN who had received multiple cycles of chemotherapy over 6 months, presenting with sudden onset and rapidly progressing unilateral vision loss. The patient had progressive disc edema with haemorrhages and rapid vision loss in the right eye from 6/9 to loss of light perception in 3 days. Interestingly on bone marrow aspiration cytology the tumour was in remission stage but contrast MRI showed swollen optic nerve sheath, indicating tumour infiltration.ConclusionThough ophthalmic involvement in BPDCN is usually orbital, very few cases of direct ocular involvement have been reported. This case is unique as haemorrhagic disc edema has never been reported in this rare malignancy. High index of suspicion of CNS involvement should be present as this carries a very poor prognosis and patients may benefit from CNS-directed therapy if administered early.