The spectrum of sleep-disordered breathing ranges from primary snoring at one end to obstructive sleep apnea and central sleep apnea at the other end. The first chapter in this book provides current state of knowledge about the mechanisms of obstructive sleep apnea and central sleep apnea and reviews emerging therapies for these disorders. Furthermore, sleep apnea usually has multifactorial causes and affects multiple organic systems resulting in increased cardiovascular morbidity, disturbing sleep quality, metabolic balance, glucose and cholesterol levels, arterial hypertension and thus increasing cardiopulmonary and vascular morbidity. The second chapter summarises the main findings in literature and provides a brief and concise differential diagnosis. The authors of the third chapter expose and discuss current evidence of neurosurgical conditions and their role in the genesis and progression of sleep apnea. They emphasise the adequate treatment and future perspectives. The following chapter examine the effect of obstructive sleep apnea syndrome (OSAS) on the eye. Different ophthalmologic disorders are associated with OSAS including floppy eyelid syndrome, retinal vein occlusion, and central serious retinopathy. The last chapter in this book is focused on QT dispersion in patients with obstructive sleep apnea, with increased QT dispersion potentially reflecting disturbed myocardial repolarisation and predisposition to cardiac arrhythmias.