We appreciate the comments from Drs Akpek and Foster on our article1 describing a patient with primary intraocular lymphoma (PIOL) in whom the vitreal interleukin (IL) 10 to IL-6 ratio was less than 1.0. We agree that establishing a diagnosis of PIOL by the demonstration of lymphoma cells in the vitreous and cerebrospinal fluid (CSF) is difficult owing to the paucity of malignant cells in fluid samples, inappropriate specimen handling, and incorrect interpretation. We also agree that a single diagnostic test for the diagnosis would be desirable; however, no such test has yet been identified.