Normal Tension and Chronic Open Angle Glaucoma and Cerebrospinal Fluid Composition

Normal tension glaucoma (NTG) and chronic open angle glaucoma (COAG) occurring progressively with optimal conventional or intraocular pressure reducing surgery are still unsolved problems in ophthalmology. The investigators would like to investigate whether or not the composition of cerebrospinal fluid (CSF) surrounding the optic nerve (ON) in these patients is pathologic under certain conditions. They therefore compare the CSF taken during optic nerve sheath fenestration with the CSF taken during a lumbar puncture. The investigators' hypothesis is that, in patients with NTG and COAG, the composition of CSF surrounding the affected ON plays an important role in promoting progressive visual function loss.