title: Correlation between optic disc area and retinal nerve fiber layer thickness: a study on scanning laser polarimetry with variable corneal compensation.
abstract: OBJECTIVE
  To evaluate if a significant increase of the peripapillary retinal nerve fiber layer (RNFL) thickness can be measured in a sample of healthy eyes by means of scanning laser polarimetry with variable corneal compensation (GDx-VCC) as the optic disc (OD) area increases.
  
  
  METHODS
  One eye each of 232 healthy subjects (mean age: 57.8 years; range:40-70) was considered. Temporal-superior-nasal-inferior-temporal average (TSNIT Avg) and OD area (area within the ellipse placed on inner border of peripapillary scleral ring) values were collected. Ellipse horizontal and vertical diameters provided on printout were used to estimate OD area using the equation: OD area = pi x horizontal radius x vertical radius. TSNIT Avg values were plotted against OD area and a multiple linear regression including age calculated.
  
  
  RESULTS
  Mean OD area was 2.19 mm(2)+/-0.45 (range: 1.23-3.59) and mean TSNIT Avg was 54.3 micro +/- 3.2 (range: 45.8-61.8). Multiple linear regression equation was TSNIT Avg=57.7-0.096 x OD Area-0.055 x Age (Pearson r=-0.146: p=0.086)
  
  
  CONCLUSIONS
  In our sample of healthy eyes, no significant correlation was found between TSNIT Avg and OD area. In spite of a shorter distance between OD and measurement ellipse margins, larger discs did not necessarily show a thicker RNFL. Probably the large inter-subject variability for RNFL thickness, and then for axonal count, was a predominant factor over OD area.
authors.affiliation: Eye Clinic, University of Trieste, Piazza dell'Ospedale 1, 34129, Trieste, Italy. stefano34127@lycos.it
authors.forename: Stefano
authors.initials: S
authors.lastname: Da Pozzo
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Iacono
authors.forename: Luca
authors.initials: L
authors.lastname: Michelone
authors.forename: Marco
authors.initials: M
authors.lastname: Paoloni
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Ravalico
mesh_terms: D000328:Adult; D000368:Aged; D001718:Birefringence; D003315:Cornea / Q000502:physiology*; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D007834:Lasers; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers; D009898:Optic Disk / Q000033:anatomy & histology*; D012165:Retinal Ganglion Cells / Q000166:cytology*