title: Threshold power levels for NPe6 photodynamic therapy.
abstract: OBJECTIVE
  To determine the threshold power levels for producing retinal and choroidal vascular occlusion using mono-L-aspartyl chlorin e6 (NPe6) photodynamic therapy; to evaluate its efficacy with longer intervals between photosensitizer injection and laser application; to determine the elapsed time between light application and appearance of angiographic changes.
  
  
  METHODS
  Pigmented and nonpigmented rabbits were injected intravenously with 2 mg/kg of NPe6 before laser irradiation of the retina-choroid. Group 1 was treated at increasing power levels; fluorescein angiograms were obtained at each fluence. Group 2 animals were exposed to laser irradiation at 5 minutes, and 1 and 3 hours postinjection to determine (by fluorescein angiography 24 hours post-treatment) if increasing the interval affected outcome. Group 3 animals underwent fluorescein angiography at 30 minutes, 1 hour, 2 hours, and 24 hours posttreatment to document the time between laser application and subsequent vessel closure.
  
  
  RESULTS
  Choroidal vessel occlusion was angiographically evident in all lesions at fluences of > or = 2.65 J/cm2 in pigmented rabbits and at > or = 0.88 J/cm2 in nonpigmented rabbits. Lesion diameter decreased as the time between injection and treatment increased. Vessel occlusion was documented at least 2 hours after treatment.
  
  
  CONCLUSIONS
  Choroidal vessel occlusion can occur at very low fluence.
authors.affiliation: LSU Eye Center, Louisiana State University Health Services Center School of Medicine, New Orleans, 70112-2234, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Kazi
authors.forename: G A
authors.initials: GA
authors.lastname: Peyman
authors.forename: M
authors.initials: M
authors.lastname: Unal
authors.forename: B
authors.initials: B
authors.lastname: Khoobehi
authors.forename: S
authors.initials: S
authors.lastname: Yoneya
authors.forename: K
authors.initials: K
authors.lastname: Mori
authors.forename: D
authors.initials: D
authors.lastname: Moshfeghi
authors.forename: A A
authors.initials: AA
authors.lastname: Moshfeghi
mesh_terms: D000818:Animals; D002829:Choroid / Q000098:blood supply / Q000473:pathology; D020256:Choroidal Neovascularization / Q000188:drug therapy* / Q000473:pathology; D005451:Fluorescein Angiography; D007275:Injections, Intravenous; D007834:Lasers; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D011166:Porphyrins / Q000627:therapeutic use*; D011817:Rabbits; D015861:Retinal Neovascularization / Q000188:drug therapy / Q000473:pathology; D013997:Time Factors
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; C053434:Talaporfin