title: Accuracy of the Heidelberg Spectralis in the alignment between near-infrared image and tomographic scan in a model eye: a multicenter study.
abstract: OBJECTIVE
  To evaluate temporal changes and predictors of accuracy in the alignment between simultaneous near-infrared image and optical coherence tomography (OCT) scan on the Heidelberg Spectralis using a model eye.
  
  
  METHODS
  Laboratory investigation.
  
  
  METHODS
  After calibrating the device, 6 sites performed weekly testing of the alignment for 12 weeks using a model eye. The maximum error was compared with multiple variables to evaluate predictors of inaccurate alignment. Variables included the number of weekly scanned patients, total number of OCT scans and B-scans performed, room temperature and its variation, and working time of the scanning laser. A 4-week extension study was subsequently performed to analyze short-term changes in the alignment.
  
  
  RESULTS
  The average maximum error in the alignment was 15 ± 6 μm; the greatest error was 35 μm. The error increased significantly at week 1 (P = .01), specifically after the second imaging study (P < .05); reached a maximum after the eighth patient (P < .001); and then varied randomly over time. Predictors for inaccurate alignment were temperature variation and scans per patient (P < .001). For each 1 unit of increase in temperature variation, the estimated increase in maximum error was 1.26 μm. For the average number of scans per patient, each increase of 1 unit increased the error by 0.34 μm.
  
  
  CONCLUSIONS
  Overall, the accuracy of the Heidelberg Spectralis was excellent. The greatest error happened in the first week after calibration, and specifically after the second imaging study. To improve the accuracy, room temperature should be kept stable and unnecessary scans should be avoided. The alignment of the device does not need to be checked on a regular basis in the clinical setting, but it should be checked after every other patient for more precise research purposes.
authors.affiliation: Department of Ophthalmology, Jacobs Retina Center at Shiley Eye Center, University of California San Diego, La Jolla, California; Clinica Oculistica, Dipartimento di Scienze Cliniche e di Comunità, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, University of Milan, Milan, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Barteselli
authors.affiliation: Department of Ophthalmology, Jacobs Retina Center at Shiley Eye Center, University of California San Diego, La Jolla, California.
authors.forename: Dirk-Uwe
authors.initials: DU
authors.lastname: Bartsch
authors.affiliation: Clinica Oculistica, Dipartimento di Scienze Cliniche e di Comunità, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, University of Milan, Milan, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Viola
authors.affiliation: Clinica Oculistica, Azienda Ospedaliera Sant'Anna, Como, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Mojana
authors.affiliation: Eye Clinic, Department of Biomedical and Clinical Science "Luigi Sacco", University of Milan, Luigi Sacco Hospital, Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Pellegrini
authors.affiliation: Department of Ophthalmology, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Kathrin I
authors.initials: KI
authors.lastname: Hartmann
authors.affiliation: Clinica Oculistica, Dipartimento di Scienze Cliniche e di Comunità, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, University of Milan, Milan, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Benatti
authors.affiliation: Department of Ophthalmology, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Leicht
authors.affiliation: Clinica Oculistica, Dipartimento di Scienze Cliniche e di Comunità, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, University of Milan, Milan, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Ratiglia
authors.affiliation: Eye Clinic, Department of Biomedical and Clinical Science "Luigi Sacco", University of Milan, Luigi Sacco Hospital, Milan, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Staurenghi
authors.affiliation: Department of Ophthalmology, Hamilton Glaucoma Center at Shiley Eye Center, University of California San Diego, La Jolla California.
authors.forename: Robert N
authors.initials: RN
authors.lastname: Weinreb
authors.affiliation: Department of Ophthalmology, Jacobs Retina Center at Shiley Eye Center, University of California San Diego, La Jolla, California. Electronic address: freeman@eyecenter.ucsd.edu.
authors.forename: William R
authors.initials: WR
authors.lastname: Freeman
mesh_terms: D002138:Calibration; D006801:Humans; D021621:Imaging, Three-Dimensional; D007259:Infrared Rays; D008954:Models, Biological; D019721:Ophthalmoscopes / Q000592:standards*; D015203:Reproducibility of Results; D012160:Retina / Q000033:anatomy & histology*; D041623:Tomography, Optical Coherence / Q000295:instrumentation*