title: Targeting of the retinal pigment epithelium (RPE) by means of a rapidly scanned continuous wave (CW) laser beam.
abstract: OBJECTIVE
  Selective treatment of the retinal pigment epithelium (RPE) by repetitively applying green micros-laser pulses is a new method for retinal diseases associated with a degradation of the RPE, which spares the neural retina. We investigated an alternative approach to realize repetitive micros-laser exposure by rapidly scanning a continuous wave (CW)-laser beam across the RPE.
  
  
  METHODS
  An Ar(+) laser beam (514 nm) with a diameter of 18.75 microm was repetitively scanned across porcine RPE samples in vitro providing an irradiation time of 1.6 micros per point on the central scan axis. RPE cell damage was investigated by means of the fluorescence viability assay Calcein-AM.
  
  
  RESULTS
  The ED(50) cell damage is 305 mJ/cm(2) when applying 10 scans with a repetition rate of 500 Hz. The threshold decreases with the number of scans, a saturation was found at 135 mJ/cm(2) with more than 500 exposures applied. The depth of focus in beam direction is 350 microm, defined by an increase of the threshold radiant exposure by 20%.
  
  
  CONCLUSIONS
  Targeting of pigmented cells with high local resolution has been proved with a laser-scanning device. Looking ahead selective RPE-treatment, the adaptation of a laser-scanning device on a slit-lamp or into a modified retina angiograph seems to be an attractive alternative to the pulsed micros laser device.
authors.affiliation: Medical Laser Center Lübeck, 23562 Lübeck, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Brinkmann
authors.forename: Norbert
authors.initials: N
authors.lastname: Koop
authors.forename: Mustafa
authors.initials: M
authors.lastname: Ozdemir
authors.forename: Clemens
authors.initials: C
authors.lastname: Alt
authors.forename: Georg
authors.initials: G
authors.lastname: Schüle
authors.forename: Charles P
authors.initials: CP
authors.lastname: Lin
authors.forename: Reginald
authors.initials: R
authors.lastname: Birngruber
mesh_terms: D000818:Animals; D006801:Humans; D066298:In Vitro Techniques; D017075:Laser Coagulation / Q000295:instrumentation; D010857:Pigment Epithelium of Eye / Q000293:injuries* / Q000601:surgery*; D012164:Retinal Diseases / Q000601:surgery*; D013552:Swine