title: Automated retinal topographic maps measured with magnetic resonance imaging.
abstract: OBJECTIVE
  Recent studies on ocular shape have raised increased interest in the peripheral characteristics of the eye, as it potentially triggers changes in the central vision. Current techniques are, however, not capable of accurately measuring the three-dimensional shape of the retina. We describe a new magnetic resonance imaging (MRI)-based method to obtain the retinal shape with high precision and use it to assess if differences in retinal shape could explain previously described trends in peripheral refraction.
  
  
  METHODS
  Twenty-one healthy subjects were examined using high-field ocular MRI. The resulting data were automatically segmented and processed to calculate the retinal topographic map. We validated the method against partial coherence interferometry and assessed the reproducibility for four subjects.
  
  
  RESULTS
  The retinal topographic maps describe the retinal shape with subpixel reproducibility (SD between sessions = 0.11 mm). Comparison with partial coherence interferometry showed a mean difference of 0.08 mm, 95% confidence interval -0.39 to 0.55 mm, with a standard deviation of 0.23 mm. The data give a possible geometric explanation for the previously described trend in myopic eyes toward relatively hyperopic refraction in the periphery, with full three-dimensional information. The retinal maps furthermore show small, submillimeter, irregularities that could have an important influence on the subjects' peripheral vision.
  
  
  CONCLUSIONS
  The possibility to quantitatively characterize the full three-dimensional retinal shape by MRI offers new ophthalmologic possibilities, such as quantitative geometric description of staphyloma. It could in addition be used as a validation technique, independent of standard optical methods, to measure the peripheral retinal shape.
authors.affiliation: Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands Department of Radiology, C.J. Gorter Center for High-Field MRI, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Jan-Willem M
authors.initials: JW
authors.lastname: Beenakker
authors.affiliation: Department of Radiology, Division of Image Processing, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Denis P
authors.initials: DP
authors.lastname: Shamonin
authors.affiliation: Department of Radiology, C.J. Gorter Center for High-Field MRI, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Webb
authors.affiliation: Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Gregorius P M
authors.initials: GP
authors.lastname: Luyten
authors.affiliation: Department of Radiology, Division of Image Processing, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Berend C
authors.initials: BC
authors.lastname: Stoel
mesh_terms: D000328:Adult; D002386:Cataract / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012160:Retina / Q000473:pathology*; D055815:Young Adult
keywords: image processing; magnetic resonance imaging (MRI); peripheral vision; retinal shape