title: Measurement of optic disc size and rim area with spectral-domain OCT and scanning laser ophthalmoscopy.
abstract: OBJECTIVE
  To compare optic disc and neuroretinal rim area measurements from spectral-domain optical coherence tomography (SD-OCT) to those from confocal scanning laser ophthalmoscopy.
  
  
  METHODS
  Seventy-one eyes from 43 normal subjects or suspected/definite glaucoma patients were prospectively enrolled. All subjects had biometry with the IOLMaster and disc/retinal nerve fiber layer imaging with Cirrus SD-OCT (Optic Disc Cube 200×200) and Heidelberg Retina Tomograph (HRT). Uncorrected disc and rim areas and measurements corrected for eye magnification with Bennett's formula (AL-corrected measurements), along with 30° sectoral rim areas, vertical cup-to-disc ratio (VCDR), and cup volume, were compared between the two devices.
  
  
  RESULTS
  The median (range) axial length (AL) was 24.2 mm (22.4-27.7 mm). Mean keratometry-corrected HRT disc area measurements were larger than AL-corrected HRT and SD-OCT measurements (P < 0.001 for both) and the difference was a function of keratometry measurements (K-readings). The AL-corrected HRT disc area and uncorrected/corrected Cirrus disc areas were not significantly different (P > 0.481). HRT rim area was larger than Cirrus measurements (P < 0.001) and the difference decreased with decreasing rim area. HRT VCDR and cup volume were significantly smaller than Cirrus measurements (P < 0.001). The correlations for sectoral rim areas between the two devices were moderate at best (intraclass correlation coefficients = 0.12-0.65).
  
  
  CONCLUSIONS
  HRT overestimated optic disc area as compared to SD-OCT. A portion of the difference in HRT and SD-OCT disc measurements is due to HRT's magnification correction algorithm. Rim area measurements from HRT were larger than from SD-OCT, likely a result of different definitions for the reference plane and differences in disc area measurements. Disc parameters from the two devices are not interchangeable.
authors.affiliation: Glaucoma Division, Jules Stein Eye Institute, UCLA, Los Angeles, California, USA.
authors.forename: Sasan
authors.initials: S
authors.lastname: Moghimi
authors.forename: Hamid
authors.initials: H
authors.lastname: Hosseini
authors.forename: Jay
authors.initials: J
authors.lastname: Riddle
authors.forename: Gina Yoo
authors.initials: GY
authors.lastname: Lee
authors.forename: Elena
authors.initials: E
authors.lastname: Bitrian
authors.forename: JoAnn
authors.initials: J
authors.lastname: Giaconi
authors.forename: Joseph
authors.initials: J
authors.lastname: Caprioli
authors.forename: Kouros
authors.initials: K
authors.lastname: Nouri-Mahdavi
mesh_terms: D005260:Female; D005901:Glaucoma / Q000175:diagnosis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009887:Ophthalmoscopy / Q000379:methods*; D009898:Optic Disk / Q000166:cytology*; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*