title: Retinal nerve fibre layer thickness in a general population in Iran.
abstract: BACKGROUND
  To determine retinal nerve fibre layer (RNFL) thickness distribution and its related factors in a general population of 45 to 69 year olds in Iran.
  
  
  METHODS
  Population-based cross-sectional study.
  
  
  METHODS
  Of the 5190 participants of phase one of Shahroud Eye Cohort Study, 4737 participated in Phase two (participation rate = 91.3%).
  
  
  METHODS
  All study participants underwent visual acuity measurement, refraction tests, slit lamp examination and ophthalmoscopic fundus exam. Tests also included imaging with Cirrus HD-OCT 4000 and its RNFL thickness data were used in this study.
  
  
  METHODS
  The overall RNFL thickness and the average RNFL thickness in different quadrants.
  
  
  RESULTS
  Mean RNFL thickness in the superior, inferior, nasal and temporal quadrants were 92.47 µm [95% confidence interval (CI): 92.14-92.80], 111.22 µm (95% CI: 110.7-111.73), 118.93 µm (95% CI: 118.31-119.55), 74.83 µm (95% CI: 74.07-75.59) and 65.48 µm (95% CI: 65.06-65.90). Multiple linear regression models indicated that RNFL thickness in all quadrants decreased with ageing, was lower in females (coefficient:-0.87 and P = 0.015), decreased by 1.42 µm (P < 0.001) for each millimetre increase in axial length and decreased by 0.41 µm (P = 0.041) for each diopter decrease in spherical equivalent refraction of myopia.
  
  
  CONCLUSIONS
  RNFL thickness in the 45 to 69-year-old Iranian population is lower compared to other studies. This difference should be noted in making disease diagnoses, particularly glaucoma. Also, there is a significant relationship between ageing and RNFL thinning in all quadrants. Longer axial length, myopia and male gender are associated with reduced RNFL thickness.
authors.affiliation: Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.affiliation: Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.|Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khabazkhoob
authors.affiliation: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
authors.forename: Payam
authors.initials: P
authors.lastname: Nabovati
authors.affiliation: Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Abbasali
authors.initials: A
authors.lastname: Yekta
authors.affiliation: Center for Health Related Social and Behavioral Sciences Research, Shahroud University of Medical Sciences, Shahroud, Iran.
authors.forename: Mohammad Hassan
authors.initials: MH
authors.lastname: Emamian
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Akbar
authors.initials: A
authors.lastname: Fotouhi
mesh_terms: D000368:Aged; D000886:Anthropometry; D058452:Axial Length, Eye / Q000033:anatomy & histology; D001699:Biometry; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007492:Iran; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers; D009900:Optic Nerve / Q000033:anatomy & histology*; D012165:Retinal Ganglion Cells / Q000166:cytology*; D041623:Tomography, Optical Coherence; D014792:Visual Acuity / Q000502:physiology
keywords: Middle East; glaucoma; population-based study; retinal nerve fibre layer