|We have described on this webpage that ocular blood flow is reduced in glaucoma and that this reduction is not only secondary. There are also primary disorders that are causally involved in glaucoma damage. In this chapter, we ask whether all or only specific forms of ocular blood flow disorders contribute to glaucoma damage. To answer this question, we must recognize the difference between glaucomatous and nonglaucomatous optic atrophy. In both forms, there is a loss of nerve fibers. In non-glaucomatous atrophy, the space thus vacated is occupied by proliferating glia, primarily astrocytes (bland optic disc atrophy). In glaucoma, on the other hand, this space remains vacant (excavated optic disc) because the astrocytes are activated first but then die. The explanation is that astrocytes survive hypoxia quite well, but are very sensitive to oxidative stress.