title: Agreement of two different spectral domain optical coherence tomography instruments for retinal nerve fiber layer measurements.
abstract: OBJECTIVE
  To determine the agreement between Spectralis and Cirrus spectral domain optical coherence tomography (SD-OCT) measurements of peripapillary retinal nerve fiber layer (RNFL) thickness.
  
  
  METHODS
  Suspected or confirmed cases of glaucoma who met the inclusion criteria underwent peripapillary RNFL thickness measurement using both the Spectralis and Cirrus on the same day within a few minutes.
  
  
  RESULTS
  Measurements were performed on 103 eyes of 103 patients with mean age of 50.4±17.7 years. Mean RNFL thickness was 89.22±15.87 versus 84.54±13.68 µm using Spectralis and Cirrus, respectively. The difference between measurements and the average of paired measurements with the two devices showed a significant linear relationship. Bland-Altman plots demonstrated that Spectralis thickness values were systematically larger than that of Cirrus.
  
  
  CONCLUSIONS
  Spectralis OCT generates higher peripapillary RNFL thickness readings as compared to Cirrus OCT; this should be kept in mind when values obtained with different instruments are compared during follow-up.
authors: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran ; Department of Ophthalmology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors: Hooshang
authors: H
authors: Faghihi
authors: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
authors: Fedra
authors: F
authors: Hajizadeh
authors: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran ; Department of Ophthalmology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors: Hassan
authors: H
authors: Hashemi
authors: Dezful University of Medical Sciences, Dezful, Iran.
authors: Mehdi
authors: M
authors: Khabazkhoob
keywords: Glaucoma; Optical Coherence Tomography; Peripapillary Retinal Nerve Fiber Layer