title: The effect of glaucoma on the optical attenuation coefficient of the retinal nerve fiber layer in spectral domain optical coherence tomography images.
abstract: OBJECTIVE
  To demonstrate the effect of glaucoma on the optical attenuation coefficient of the retinal nerve fiber layer (RNFL) in Spectral Domain Optical Coherence Tomography (SD-OCT) images.
  
  
  METHODS
  We analyzed images of the peripapillary areas in 10 healthy and 30 glaucomatous eyes (mild, moderate, and advanced glaucoma, 10 eyes each), scanned with the Spectralis OCT (Heidelberg Engineering GmbH, Dossenheim, Germany). To calculate the RNFL attenuation coefficient (μ(att)), determined by the scattering properties of the RNFL, we used a model that normalized the reflectivity of the RNFL by the retinal pigment epithelium. The analysis was performed at four preset locations at 1.3 and 1.7 mm from the center of the optic nerve head (ONH) (i.e., temporally, superiorly, nasally, and inferiorly) and on averages per eye. To assess the structure-function relationship, we correlated the μ(att) to the mean deviation (MD) in standard automated perimetry.
  
  
  RESULTS
  The μ(att) of the RNFL decreased up to 40% with increasing disease severity, on average as well as in each location around the ONH (Jonckheere-Terpstra test, P < 0.019 in all tests). The μ(att) of the RNFL depended significantly on the location around the ONH in all eyes (Kruskal-Wallis test, P < 0.014) and was lowest nasally from the ONH. The μ(att) correlated significantly with the MD in SAP (R(2) = 0.337).
  
  
  CONCLUSIONS
  The measurements clearly demonstrated that the μ(att) of the RNFL decreased with increasing disease severity. The RNFL attenuation coefficient may serve as a new method to quantify glaucoma in SD-OCT images.
authors.affiliation: the    Rotterdam Ophthalmic Institute and.
authors.forename: Josine
authors.initials: J
authors.lastname: van der Schoot
authors.forename: Koenraad A
authors.initials: KA
authors.lastname: Vermeer
authors.forename: Johannes F
authors.initials: JF
authors.lastname: de Boer
authors.forename: Hans G
authors.initials: HG
authors.lastname: Lemij
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D005901:Glaucoma / Q000473:pathology*; D006801:Humans; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009900:Optic Nerve / Q000473:pathology*; D012160:Retina / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000379:methods*; D014792:Visual Acuity; D014794:Visual Fields