The consequences of sleep apneas in patients with obstructive sleep apnea (OSA) syndrome may influence the function of visual system. In 21 patients with OSA syndrome (apnea/hypopnea index--AHI 50+/-20) the detailed ophthalmologic studies, including tonometry, biomicroscopic evaluation of the anterior segment of the eye, automatic perimetry and stereoscopic examination of the eye fundus have been performed. In 4 patients (19%) the signs of lesions in the optic tract have been found. These were: defects in visual field caused by glaucoma (primary open-angle glaucoma and normal-tension glaucoma) in 2 patients and defects in visual field (concentric and quadrantic homonymous) caused by diffuse lesions in the cortico-nuclear tract in 2 patients. In patients with the lesions in the optic tract there were severe disorders of breathing during sleep: AHI >60, mean SaO2 at the end of the apneas <86% and minimal SaO2 at the end of the apneas <70%. The authors conclude that in OSA patients there is a high risk of the lesions of the optic tract as a consequence of severe and repetitive hypoxemia during sleep.