gms | German Medical Science

102. Jahrestagung der DOG

Deutsche Ophthalmologische Gesellschaft e. V.

23. bis 26.09.2004, Berlin

Selective RPE-laser therapy with a laser scanner

Meeting Abstract

  • corresponding author C. Framme - University Eye Hospital, Regensburg; Wellman Laboratories of Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, USA
  • C. Alt - Medical Laser Center Lübeck, Lübeck
  • S. Schnell - Medical Laser Center Lübeck, Lübeck
  • R. Brinkmann - Medical Laser Center Lübeck, Lübeck
  • C. P. Lin - Wellman Laboratories of Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, USA

Evidenzbasierte Medizin - Anspruch und Wirklichkeit. 102. Jahrestagung der Deutschen Ophthalmologischen Gesellschaft. Berlin, 23.-26.09.2004. Düsseldorf, Köln: German Medical Science; 2004. Doc04dogDO.12.08

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Veröffentlicht: 22. September 2004

© 2004 Framme et al.
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A selective RPE laser therapy with sparing of the neurosensory layer is possible by applying repetitive microsecond laser pulses. Macular diseases such as diabetic maculopathy, drusen maculopathy or central serous retinopathy were shown to be treated successfully by this technique. It was the aim of this study to show, if selectivity could also be achieved using a conventional green cw-laser by scanning the beam across the retina during irradiation.


A cw-laser beam at 532nm was coupled to a slitlamp using a two-dimensional acusto-optical deflector. The spot (18μm) was focused and scanned across the retina of Dutch-belted rabbits through a contact lens. The scan-field was 300x300μm in size and consisted of six separate scan lines. The scanning speed was 3.6 μm/μs, equivalent to 1 spot diameter per 5μs, and the entire scan field was repeated 100 times at a frame rate of 100Hz. ED50-thresholds for RPE damage were calculated by fluorescein angiographic leakage in irradiated areas after exposure to different laser intensities. The extent of selectivity was examined by lightmicroscopy.


Clinically the selective laser-induced RPE defect was demonstrated by fluorescein angiographic leakage and concurrent absence of ophthalmoscopic visibility. The angiographic ED50-damage threshold for the 100 scans was 68 mW (161mJ/cm2). Ophthalmoscopic visibility was not noticed even with the maximum available laser power of 180 mW (438mJ/cm2). Thus the therapeutic window between angiographic and ophthalmoscopic thresholds had a factor of at least 2.7. Histologic examinations revealed selective RPE destruction with intact photoreceptors for irradiation at laser power levels 2 times above angiographic threshold.


Selective RPE damage is demonstrated using a conventional green cw-laser when scanning the focused laser beam across the fundus with a speed such that every single cell is irradiated for a duration of 5μs. With a therapeutic window of >2.7 selective treatment of the RPE is possible when intra- and interindividual pigment variation of a factor of about 2 in humans is considered.