title: Evaluation of the influence of tilt of optic disc on the measurement of optic disc variables obtained by optical coherence tomography and confocal scanning laser ophthalmoscopy.
abstract: OBJECTIVE
  To evaluate the relationship between optic disc variables measured by confocal scanning laser ophthalmoscopy (CSLO) and optical coherence tomography (OCT).
  
  
  METHODS
  Fifty-one eyes in 27 non-glaucomatous patients were scanned using a CSLO-TopSStrade mark and an OCT-OCT 3000trade mark. The relationship between the following four optic disc variables-disc area (DA), cup area (CA), neuroretinal rim area (NRRA), and cup-disc area ratio (CDAR)-measured by CSLO and OCT were evaluated, and the relationship between these measurements and optic disc tilt was assessed. Horizontal (HD) and vertical diameters (VD) of the optic disc were measured from disc photographs, and by CSLO and OCT, and ratios (HD/VD) were then compared.
  
  
  RESULTS
  There was a good correlation in DA, CA, and CDAR except NRRA between OCT and CSLO measurements. In eyes with a tilt >/=4 degrees, DA and NRRA were measured larger, and CDAR and CA were measured smaller by OCT than by CSLO. However, in the eyes with a tilt of <4 degrees, no significant differences in measurement of disc variables were observed for the two measurement systems. HD/VD measured from disc photographs was well correlated with those determined by CSLO (r = 0.741, P < 0.0001), however, it correlated poorly with those measured by OCT in whole study eyes (r = 0.410, P = 0.008) and in eyes tilted by >/=4 degrees, respectively (P = 0.280).
  
  
  CONCLUSIONS
  Although CSLO and OCT measurements of the optic disc are highly correlated, discrepancy becomes prominent in eyes with a disc tilted >/=4 degrees. Therefore, analysis of the optic nerve head by OCT must be cautiously interpreted in eyes with a highly tilted disc.
authors.affiliation: Department of Ophthalmology, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, Korea.
authors.forename: Choul Yong
authors.initials: CY
authors.lastname: Park
authors.forename: Yun Taek
authors.initials: YT
authors.lastname: Kim
authors.forename: Changwon
authors.initials: C
authors.lastname: Kee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001284:Atrophy; D005260:Female; D006801:Humans; D007834:Lasers; D008297:Male; D008875:Middle Aged; D009887:Ophthalmoscopy / Q000379:methods*; D009898:Optic Disk / Q000002:abnormalities* / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D010781:Photography; D010857:Pigment Epithelium of Eye / Q000473:pathology; D041623:Tomography, Optical Coherence / Q000379:methods*