title: Real-time in vivo imaging of retinal cell apoptosis after laser exposure.
abstract: OBJECTIVE
  To investigate whether the detection of apoptosing retinal cells (DARC) could detect cells undergoing apoptosis in a laser model of retinal damage.
  
  
  METHODS
  Laser lesions were placed, with the use of a frequency-doubled Nd:YAG laser, on the retina in 34 eyes of anesthetized Dark Agouti rats. Lesion size and laser-induced retinal elevation were analyzed using in vivo reflectance imaging. Development of retinal cell apoptosis was assessed using intravitreal fluorescence-labeled annexin 5 in vivo with DARC technology from baseline until 90 minutes after laser application. Histologic analysis of retinal flat mounts and cross-sections was performed.
  
  
  RESULTS
  The lateral and anteroposterior depth extension of the zone of laser damage was significantly larger for higher exposure settings. A strong diffuse signal, concentrated at the outer retina, was seen with DARC for low exposures (<300 ms and <300 mW). In comparison, higher exposures (>300 ms and >300 mW) resulted in detectable hyperfluorescent spots, mainly at the level of the inner retinal layers. Dose-dependent effects on spot density and positive correlation of spot density between lesion size (P < 0.0001) and retinal elevation (P < 0.0001) were demonstrated. Histology confirmed the presence of apoptosing retinal cells in the inner nuclear and the ganglion cell layers.
  
  
  CONCLUSIONS
  This is the first time that DARC has been used to determine apoptotic effects in the inner nuclear layer. The ability to monitor changes spatially and temporally in vivo promises to be a major advance in the real-time assessment of retinal diseases and treatment effects.
authors.affiliation: Institute of Ophthalmology, University College London, London, United Kingdom.
authors.forename: Steffen
authors.initials: S
authors.lastname: Schmitz-Valckenberg
authors.forename: Li
authors.initials: L
authors.lastname: Guo
authors.forename: Annelie
authors.initials: A
authors.lastname: Maass
authors.forename: William
authors.initials: W
authors.lastname: Cheung
authors.forename: Anthony
authors.initials: A
authors.lastname: Vugler
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Moss
authors.forename: Peter M G
authors.initials: PM
authors.lastname: Munro
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Fitzke
authors.forename: M Francesca
authors.initials: MF
authors.lastname: Cordeiro
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis; D003199:Computer Systems; D005456:Fluorescent Dyes; D007091:Image Processing, Computer-Assisted; D053844:Lasers, Solid-State; D008297:Male; D051381:Rats; D012160:Retina / Q000473:pathology* / Q000601:surgery*
chemical_list: D017304:Annexin A5; D005456:Fluorescent Dyes