title: Changes of Retinal Nerve Fiber Layer Thickness in Obstructive Sleep Apnea Syndrome: A Systematic Review and Meta-analysis.
abstract: Many studies have assessed the changes of retinal nerve fiber layer (RNFL) thickness in patients with obstructive sleep apnea syndrome (OSAS), but the results were inconsistent. Therefore, a meta-analysis was performed to evaluate the RNFL changes in OSAS measured in vivo.
  
  
  
  Pertinent studies were identified by a comprehensive search of PubMed, Embase, Web of science, Cochrane library, Scopus, and Chinese biomedical disc databases from inception to August 2016. A fixed effects model was used to pool the weighted mean difference (WMD) and 95% confidence interval (CI) between OSAS group and control group.
  
  
  
  Seventeen studies were included in the final analysis, with 12 for descriptive analysis and 5 for meta-analysis, involving a total of 1757 eyes (1106 in the OSAS group and 651 in the control group). The RNFL in OSAS was significantly lower than control group, with pooled WMD -3.53 (95%CI: -4.80 to -2.26, P < 0.001) for average RNFL, -3.69 (95%CI:-5.49 to -1.89 P < 0.001) for superior RNFL, -4.66 (95%CI: -6.92 to -2.39, P < 0.001) for inferior RNFL, -3.15 (95%CI:-5.19 to -1.10, P = 0.003) for nasal RNFL, and -2.45 (95%CI: -4.59 to -0.31, P = 0.025) for temporal RNFL. Along with severities of OSAS, a trend of more profound reduction of average RNFL was observed in advanced OSAS, with WMD of average RNFL thickness -1.75 (95%CI:-4.47 to -0.98, P = 0.209) for mild OSAS, -3.54 (95%CI:-6.33 to -0.73, P = 0.013) for moderate OSAS, and -7.17 (95%CI:-10.00 to -4.34, P < 0.001) for severe OSAS. The majority of studies in the descriptive review demonstrated similar findings.
  
  
  
  The OSAS was associated with a reduced RNFL in all quadrants compared to controls. Evaluation of RNFL may serve as a tool for grading severities of OSAS. Considering the limited evidence, the conclusions should be interpreted cautiously.
authors.affiliation: a Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology , Sun Yat-Sen University , Guangzhou , People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: a Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology , Sun Yat-Sen University , Guangzhou , People's Republic of China.
authors.forename: Miao
authors.initials: M
authors.lastname: He
authors.affiliation: a Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology , Sun Yat-Sen University , Guangzhou , People's Republic of China.
authors.forename: Wenyong
authors.initials: W
authors.lastname: Huang
mesh_terms: D018450:Disease Progression; D006801:Humans; D009412:Nerve Fibers / Q000473:pathology*; D012164:Retinal Diseases / Q000175:diagnosis* / Q000209:etiology; D012165:Retinal Ganglion Cells / Q000473:pathology*; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000175:diagnosis; D041623:Tomography, Optical Coherence / Q000379:methods
keywords: Meta-analysis; obstructive sleep apnea syndrome; optic coherence tomography; retinal nerve fiber layer thickness