title: Melanin Pigmentation in Rat Eyes: In Vivo Imaging by Polarization-Sensitive Optical Coherence Tomography and Comparison to Histology.
abstract: OBJECTIVE
  The purpose of this study was to demonstrate polarization-sensitive optical coherence tomography (PS-OCT) for imaging pigmented structures in the posterior eye segments of albino and pigmented rats and to correlate depolarization contrast of the retinal pigment epithelium (RPE) and choroid in in vivo PS-OCT to melanin pigmentation detected in postmortem histologic serial sections.
  
  
  METHODS
  In vivo three-dimensional PS-OCT imaging was performed in adult albino and pigmented rat eyes at 70-kHz A-line rate. Degree of polarization uniformity (DOPU) fundus maps and radial DOPU profiles were generated. Postmortem histomorphologic analysis was performed in order to investigate melanin pigmentation of the RPE and choroid. Fundus pigmentation maps were extracted from histologic serial sections. Pigmentation profiles were correlated to DOPU profiles of the same eyes.
  
  
  RESULTS
  Strong depolarization was found in the RPE/choroid complex of pigmented rats, whereas the same structures exhibited uniform polarization in albino rats. The difference between the depolarization characteristics between albino and pigmented animals was statistically significant. In the fundus pigmentation maps, optical pigment density was zero in albino rat eyes. In pigmented rat eyes, a strong negative correlation between optical pigment density and DOPU was observed.
  
  
  CONCLUSIONS
  This in vivo and ex vivo investigation of posterior rat eyes indicates that melanin is the cause of depolarization in retinal PS-OCT images. It further demonstrates that melanin pigmentation in the RPE and choroid can be quantified via depolarization imaging and therefore suggests that PS-OCT is a useful tool for the noninvasive quantitative assessment of pigmentary changes in vision-threatening diseases such as age-related macular degeneration.
authors.affiliation: Center for Medical Physics and Biomedical Engineering Medical University of Vienna, Vienna, Austria.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Baumann
authors.affiliation: Center for Medical Physics and Biomedical Engineering Medical University of Vienna, Vienna, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Schirmer
authors.affiliation: Core Facility Imaging, Medical University of Vienna, Vienna, Austria.
authors.forename: Sabine
authors.initials: S
authors.lastname: Rauscher
authors.affiliation: Center for Medical Physics and Biomedical Engineering Medical University of Vienna, Vienna, Austria.
authors.forename: Stanislava
authors.initials: S
authors.lastname: Fialová
authors.affiliation: Core Facility for Research and Technology, University of Veterinary Medicine Vienna, Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Glösmann
authors.affiliation: Center for Medical Physics and Biomedical Engineering Medical University of Vienna, Vienna, Austria.
authors.forename: Marco
authors.initials: M
authors.lastname: Augustin
authors.affiliation: Center for Medical Physics and Biomedical Engineering Medical University of Vienna, Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Pircher
authors.affiliation: Core Facility Imaging, Medical University of Vienna, Vienna, Austria.
authors.forename: Marion
authors.initials: M
authors.lastname: Gröger
authors.affiliation: Center for Medical Physics and Biomedical Engineering Medical University of Vienna, Vienna, Austria.
authors.forename: Christoph K
authors.initials: CK
authors.lastname: Hitzenberger
mesh_terms: D000417:Albinism / Q000473:pathology*; D000818:Animals; D004195:Disease Models, Animal; D005451:Fluorescein Angiography; D005654:Fundus Oculi; D008297:Male; D008543:Melanins / Q000378:metabolism*; D051381:Rats; D011914:Rats, Inbred BN; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley; D055213:Retinal Pigment Epithelium / Q000378:metabolism / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000379:methods*; D014792:Visual Acuity
chemical_list: D008543:Melanins