 STRATEGY OF ANALYSIS The clinical experiment aims to compare the vascular regulation of the optic nerve in OSA patients with that of a healthy group of human subjects. Subsequently, a group of OSA patients with NAION will be analyzed in order to compare the ocular blood flow ant its regulation in eyes with ischemic neuropathy NAION with eyes of OSA patients without optic nerve disease. All these comparisons will allow to characterize the optic nerve blood flow in healthy eyes, in eyes of OSA patients and in eyes of OSA patients at the time of acute ischemic attack NAION.The glaucoma patients will be compared with healthy subjects. 