In a clinical trial with 222 lymphoma patients, nine of them had ocular adverse effects such as conjunctivitis, transitory ocular edema, a burning sensation, and a transient or permanent, even severe, loss of visual function. > span These problems were caused by the monoclonal antibody Rituximab. It is used to treat cancer, but it can also cause serious side effects. In this article we will explain what role Rituximab plays in the treatment of cancer and why it may be difficult for some people to stop taking it. Cancer Treatment: Rituximab blocks proteins called CD20 that are found on certain types of white blood cells (B-cells) and on certain cancer cells. By blocking these proteins, Rituximab prevents B-cells from producing antibodies against other substances (antigens) that would normally tell their body's immune system to attack foreign objects such as cancer cells. This means that Rituximab can prevent your body from creating its own defenses against cancer. As a result, Rituximab can help destroy tumors by causing the patient's immune system to fight off cancer cells. Rituximab is used in combination with other treatments for non-Hodgkin's lymphomas.