This CPB has been revised to state that the following are considered experimental and investigational: (i) measurement of central corneal thickness, intra-ocular pressure, and retinal nerve fiber layer thickness for grading severities of obstructive sleep apnea syndrome (OSAS); (ii) measurement of Fas-positive lymphocytes for evaluation of systemic inflammation in OSAS; (iii) upper gastro-intestinal endoscopy for diagnosing OSAS; and (iv) use of serum level of advanced glycation end-products as a biomarker of obstructive sleep apnea-hypopnea syndrome.