title: Fluorescence lifetime imaging of the ocular fundus in mice.
abstract: OBJECTIVE
  Fundus autofluorescence (AF) is characterized not only by its intensity or excitation and emission spectra but also by the lifetimes of the fluorophores. Fluorescence lifetime is influenced by the fluorophore's microenvironment and may provide information about the metabolic tissue state. We report quantitative and qualitative autofluorescence lifetime imaging of the ocular fundus in mice.
  
  
  METHODS
  A fluorescence lifetime imaging ophthalmoscope (FLIO) was used to measure fluorescence lifetimes of endogenous fluorophores in the murine retina. FLIO imaging was performed in 1-month-old C57BL/6, BALB/c, and C3A.Cg-Pde6b(+)Prph2(Rd2)/J mice. Measurements were repeated at monthly intervals over the course of 6 months. For correlation with structural changes, an optical coherence tomogram was acquired.
  
  
  RESULTS
  Fundus autofluorescence lifetime images were readily obtained in all mice. In the short spectral channel (498-560 nm), mean ± SEM AF lifetimes were 956 ± 15 picoseconds (ps) in C57BL/6; 801 ± 35 ps in BALB/c mice; and 882 ± 37 ps in C3A.Cg-Pde6b(+)Prph2(Rd2)/J mice. In the long spectral channel (560-720 nm), mean ± SEM AF lifetimes were 298 ± 14 ps in C57BL/6 mice, 241 ± 10 ps in BALB/c mice, and 288 ± 8 ps in C3A.Cg-Pde6b(+)Prph2(Rd2)/J mice. There was a general decrease in mean AF lifetimes with age.
  
  
  CONCLUSIONS
  Although fluorescence lifetime values differ among mouse strains, we found little variance within the groups. Fundus autofluorescence lifetime imaging in mice may provide additional information for understanding retinal disease processes and may facilitate monitoring of therapeutic effects in preclinical studies.
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.affiliation: Department of Ophthalmology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.
authors.forename: Muriel
authors.initials: M
authors.lastname: Dysli
authors.affiliation: Department of Ophthalmology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.
authors.forename: Volker
authors.initials: V
authors.lastname: Enzmann
authors.affiliation: Department of Ophthalmology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wolf
authors.affiliation: Department of Ophthalmology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.
authors.forename: Martin S
authors.initials: MS
authors.lastname: Zinkernagel
mesh_terms: D000818:Animals; D005654:Fundus Oculi; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009887:Ophthalmoscopy; D061848:Optical Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012160:Retina / Q000166:cytology*; D041623:Tomography, Optical Coherence / Q000379:methods*
keywords: fluorescence lifetimes; fundus autofluorescence; mouse models; ophthalmic imaging; validation studies