How does lowering of intraocular pressure protect the optic nerve?

Until recently, the evidence that lowering intraocular pressure (IOP) protects the optic nerve from glaucomatous damage was weak. Several randomized controlled trials have provided stronger evidence that lowering IOP prevents glaucomatous progression. Optic nerves appear to be highly variable in their susceptibility to raised IOP. Elevated IOP likely triggers several parallel, but interacting mechanisms, including direct axonal damage, failure of load-bearing tissues, and disturbances in microvascular supply. The cellular mechanisms that translate these mechanical and physiologic stresses and that lead to excavation of optic nerve tissue are beginning to be understood.