title: Normal-tension glaucoma and obstructive sleep apnea syndrome: a prospective study.
abstract: BACKGROUND
  Today, identified risk factors for normal-tension glaucoma (NTG) include abnormal ocular blood flow, abnormal blood coagulation, systemic hypotension, ischemic vascular disorders, and autoimmune diseases. However, pathogenesis of the condition remains unclear. On the other hand, there are also a few studies suggesting that the obstructive sleep apnea syndrome (OSAS) may compromise optic nerve head perfusion and cause glaucomatous optic neuropathy by creating transient hypoxemia and increasing vascular resistance. In this study, we evaluated the possible association between OSAS and NTG.
  
  
  METHODS
  We recruited 24 patients with NTG and 24 age and sex matched controls who were also similar for systemic risk factors such as diabetes mellitus (DM), hypertension (HT) and hypercholesterolemia. All patients and controls underwent over-night polysomnography (PSG) for the diagnosis of OSAS and calculation of Apnea-Hypopnea Index (AHI).
  
  
  RESULTS
  Patients and controls were statistically similar in terms of age, sex, gender, smoking, systemic risk factors, neck circumference and body mass index. The subjects with AHI ≥ 20 were accepted as OSAS. Ten (41.7%) of 24 patients with NTG and 3 (12.5%) of 24 controls had OSAS (p < 0.05).
  
  
  CONCLUSIONS
  The prevalence of OSAS was higher in patients with NTG and the difference between patient and control groups was statistically significant (p < 0.05).
authors.affiliation: Ophthalmologist, Hacettepe University Gün Hospital, Beytepe, 06800 Ankara, Turkey. gorkemgencebilgin@gmail.com.
authors.forename: Gorkem
authors.initials: G
authors.lastname: Bilgin
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D057066:Low Tension Glaucoma / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D015995:Prevalence; D011446:Prospective Studies; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000453:epidemiology