RESUMEN
Optic nerve infiltration is a rare but known complication of the central nervous system (CNS)-involving lymphoma and leukemic disorders. The diagnosis is often presumed and patients are empirically treated with systemic therapy and/or local radiation. Optic nerve biopsy is usually avoided due to the risk of permanent vision loss secondary to the procedure. We present a case of biopsy-proven leukemic optic neuropathy without optic nerve sheath or cerebrospinal fluid (CSF) involvement in a patient previously in remission from T-cell prolymphocytic leukemia (T-PLL). To our knowledge, this is the first documented case of T-PLL with biopsy-proven optic nerve invasion without CSF involvement and suggests possible perineural invasion or a sanctuary site from chemotherapy. We suggest that for patients with poor vision and suspected leukemic infiltration without other evidence of CNS involvement, both optic nerve and optic sheath biopsy should be performed for diagnosis and treatment.