Primary intraocular lymphoma (PIOL) is a subtype of primary central nervous system (CNS) lymphoma (PCNSL) that mainly originates from the retina or retinal pigment epithelium, with vitreous involvement. PIOL is usually an aggressive large B cell-type lymphoma with progressive optic nerve and CNS involvement. Approximately 60–80 % of patients with PIOL exhibit brain involvement either at diagnosis or during follow-up. The average age of onset is 54 years (36–90 years); however, reports concerning sex-based predilections are contradictory. The main clinical manifestations of PIOL are painless blurred vision and floaters, and up to 80 % of cases exhibit bilateral eye involvement. Considering the nonspecific ophthalmologic manifestations of this disease, diagnosis may be delayed up to 2 years after the initial presentation. The presence of abnormal lymphoid cells in vitrectomy samples establishes a diagnosis of PIOL, and flow cytometric analysis can confirm the monoclonality of malignant B cells. Most reports of PIOL are from Western countries, while those from Asian populations are scarce.
　　A standard treatment for patients with primary intraocular lymphoma (PIOL) remains unclear. This study retrospectively analyzed the clinical features and outcomes of 19 patients with PIOL who were treated with a first-line therapy comprising combined intravenous high-dose methotrexate and intravitreal methotrexate between January 2003 and December 2013. Thirteen (68.4 %) patients were female, and the median age at diagnosis was 57 (39–77 years). Diagnoses were based on the identification of abnormal lymphoid cells in vitreous fluid. Ten (52.6 %) patients had bilateral eye involvement, and six had concurrent central nervous system (CNS) involvement. All 19 patients achieved complete remission (CR) as confirmed by cytological examination of vitreous and cerebrospinal fluid and brain imaging if CNS was involved. Patients with concurrent brain involvement required a longer time to achieve CR. However, the duration of complete remission did not differ between patients with and without CNS involvement. The 5-year overall survival rate was 55.8 % for the total cohort and was higher (68.8 %) in patients with isolated PIOL than in those with concurrent CNS involvement. In all patients, methotrexate treatment was well tolerated, with manageable side effects. We conclude that combined intravitreal methotrexate and systemic high-dose methotrexate treatment is effective in patients with PIOL.