title: Quantitative analysis of fluorescence lifetime measurements of the macula using the fluorescence lifetime imaging ophthalmoscope in healthy subjects.
abstract: OBJECTIVE
  Fundus autofluorescence (FAF) cannot only be characterized by the intensity or the emission spectrum, but also by its lifetime. As the lifetime of a fluorescent molecule is sensitive to its local microenvironment, this technique may provide more information than fundus autofluorescence imaging. We report here the characteristics and repeatability of FAF lifetime measurements of the human macula using a new fluorescence lifetime imaging ophthalmoscope (FLIO).
  
  
  METHODS
  A total of 31 healthy phakic subjects were included in this study with an age range from 22 to 61 years. For image acquisition, a fluorescence lifetime ophthalmoscope based on a Heidelberg Engineering Spectralis system was used. Fluorescence lifetime maps of the retina were recorded in a short- (498-560 nm) and a long- (560-720 nm) spectral channel. For quantification of fluorescence lifetimes a standard ETDRS grid was used.
  
  
  RESULTS
  Mean fluorescence lifetimes were shortest in the fovea, with 208 picoseconds for the short-spectral channel and 239 picoseconds for the long-spectral channel, respectively. Fluorescence lifetimes increased from the central area to the outer ring of the ETDRS grid. The test-retest reliability of FLIO was very high for all ETDRS areas (Spearman's ρ = 0.80 for the short- and 0.97 for the long-spectral channel, P < 0.0001). Fluorescence lifetimes increased with age.
  
  
  CONCLUSIONS
  The FLIO allows reproducible measurements of fluorescence lifetimes of the macula in healthy subjects. By using a custom-built software, we were able to quantify fluorescence lifetimes within the ETDRS grid. Establishing a clinically accessible standard against which to measure FAF lifetimes within the retina is a prerequisite for future studies in retinal disease.
authors.affiliation: Department of Ophthalmology, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland.
authors.forename: Chantal
authors.initials: C
authors.lastname: Dysli
authors.forename: Gwénolé
authors.initials: G
authors.lastname: Quellec
authors.forename: Mathias
authors.initials: M
authors.lastname: Abegg
authors.forename: Marcel N
authors.initials: MN
authors.lastname: Menke
authors.forename: Ute
authors.initials: U
authors.lastname: Wolf-Schnurrbusch
authors.forename: Jens
authors.initials: J
authors.lastname: Kowal
authors.forename: Johannes
authors.initials: J
authors.lastname: Blatz
authors.forename: Olivier
authors.initials: O
authors.lastname: La Schiazza
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Leichtle
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wolf
authors.forename: Martin S
authors.initials: MS
authors.lastname: Zinkernagel
mesh_terms: D000328:Adult; D005260:Female; D005451:Fluorescein Angiography / Q000379:methods*; D005500:Follow-Up Studies; D005654:Fundus Oculi; D006801:Humans; D008266:Macula Lutea / Q000166:cytology*; D008297:Male; D008875:Middle Aged; D019721:Ophthalmoscopes; D009887:Ophthalmoscopy / Q000379:methods*; D012016:Reference Values; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014792:Visual Acuity; D055815:Young Adult
keywords: fluorescence lifetimes; fundus autofluorescence; macula; validation studies