Glaucoma and dysfunction of axonal transport: One of the leading causes of irreversible blindness worldwide is glaucoma, with increased intraocular pressure (IOP) being the most common risk factor. However, in some glaucoma patients it has been shown that the IOP does not differ from that of the normal population. In Japan, normal-tension glaucoma (NTG), which accounts for 92％ of primary open-angle glaucoma, has been shown to be more frequent in the population.