title: Transpupillary thermotherapy threshold parameters: funduscopic, angiographic, and histologic findings in pigmented and nonpigmented rabbits.
abstract: OBJECTIVE
  To evaluate the effect of pigmentation on threshold fluence levels, needed to produce visible and angiographic lesions, of transpupillary thermotherapy (TTT) in rabbits.
  
  
  METHODS
  Six pigmented and nine nonpigmented rabbits underwent TTT with an 810-nm diode laser coupled to a slit-lamp biomicroscope using a spot size of 2 or 3 mm. The power ranged from 80 to 200 mW with 1 to 3 minutes of laser exposure for pigmented rabbits and 750 to 1800 mW with 1 minute of exposure for albino rabbits. These parameters were also evaluated after compression of the globe using the contact lens to induce blanching of the optic nerve head. After the experiment, the eyes were enucleated under deep anesthesia, and the animals were killed immediately.
  
  
  RESULTS
  In pigmented rabbits, the threshold fluence with the 2-mm spot size was 229 J/cm2 without compression and 153 J/cm2 with compression. With the 3-mm spot size, the threshold decreased from 200 to 150 mW as the duration of exposure lengthened (2 or 3 minutes), increasing the fluence from 170 to 382 J/cm2. In nonpigmented rabbits, the threshold fluence with the 2-mm spot size was 2,865 J/cm2 without compression and 2,674 J/cm2 with compression. With the 3-mm spot size, the threshold fluence of 1,528 J/cm2 was not affected by compression. Histopathologic studies showed transretinal damage at the lowest levels necessary to achieve angiographic evidence of a treatment lesion or a barely visible funduscopic lesion at the time of treatment.
  
  
  CONCLUSIONS
  Nonpigmented rabbits required more than a 12-fold increase in total TTT fluence compared with pigmented rabbits with the 2-mm spot size and a ninefold increase with the 3-mm spot size. Inner and outer retinal damage was seen histopathologically at these levels.
authors.affiliation: Department of Ophthalmology, Tulane University Health Sciences Center, New Orleans, Louisiana 70112-2699, USA. mchiass1@tulane.edu
authors.forename: Gholam A
authors.initials: GA
authors.lastname: Peyman
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Genaidy
authors.forename: Darius M
authors.initials: DM
authors.lastname: Moshfeghi
authors.forename: Fatemah
authors.initials: F
authors.lastname: Ghahramani
authors.forename: Shin
authors.initials: S
authors.lastname: Yoneya
authors.forename: Gamze
authors.initials: G
authors.lastname: Men
authors.forename: Po-Cheng
authors.initials: PC
authors.lastname: Kuo
authors.forename: Yanno
authors.initials: Y
authors.lastname: Bezerra
authors.forename: Yoko
authors.initials: Y
authors.lastname: Nishiyama-Ito
mesh_terms: D000818:Animals; D001831:Body Temperature; D005131:Eye Injuries / Q000209:etiology* / Q000473:pathology; D005451:Fluorescein Angiography; D006979:Hyperthermia, Induced; D017075:Laser Coagulation / Q000009:adverse effects*; D023421:Models, Animal; D009887:Ophthalmoscopy; D010857:Pigment Epithelium of Eye / Q000502:physiology*; D011680:Pupil; D011817:Rabbits; D011836:Radiation Tolerance; D012160:Retina / Q000293:injuries* / Q000473:pathology / Q000601:surgery; D012164:Retinal Diseases / Q000209:etiology* / Q000473:pathology; D012684:Sensory Thresholds; D013997:Time Factors