We will test the hypothesis that the direct intraventricular injection of Rituximab in combination with Methotrexate is safe and when used in combination in patients with recurrent brain and intraocular lymphoma. We will evaluate the safety of this combination by testing different dose levels of Rituximab. We will also measure the concentration of Rituximab in the intraocular compartments and cerebrospinal fluid at different time points after intraventricular administration to determine the pharmacokinetics of intrathecal Rituximab as well as the potential impact of Methotrexate on Rituximab distribution.