Additional Study Information: Glaucoma is a given name of a group of diseases that affect the retinal ganglion cells in the eye and the optic nerve. Glaucoma cause degeneration of the retinal ganglion cells in the retina and their projections (axons) that form the optic nerve. Retinal ganglion cells and their axons transmit all of our vision information from the eye to the brain through the optic nerve. As these cells die from glaucoma, patients experience progressive vision loss. We hope to learn about the safety and efficacy of a possible new treatment called NT-501 encapsulated cell therapy (ECT) implant. This is an implant that releases a drug directly into the back of the eye called ciliary neurotrophic factor(CNTF) on patients with visual impairment secondary to glaucoma. CNTF is a protein that has been shown to be effective in stopping retinal ganglion cell loss in animals with experimental glaucoma. CNTF will be delivered into the fluid of your eye by the NT-501 implant, that slowly releases the CNTF into your eye over a long period of time. NT-501 encapsulated cell therapy (ECT) is an investigational drug. This means that the drug has not been approved by the Food and Drug Administration (FDA) for medical use in patients, but has only been approved for use inresearch.