Selective targeting of the retinal pigment epithelium in rabbit eyes with a scanning laser beam

Carsten Framme, Clemens Alt, Susanne Schnell, Margaret Sherwood, Ralf Brinkmann, Charles P. Lin*

*Corresponding author for this work
16 Citations (Scopus)


PURPOSE. Selective targeting of the retinal pigment epithelium (RPE) with repetitive laser pulses that minimize thermal damage to the adjacent photoreceptors is a promising new therapeutic modality for RPE-related retinal diseases. The selectivity of an alternative, more versatile scanning approach was examined in vivo by using a broad range of scanning parameters. METHODS. Acousto-optic deflectors repeatedly scanned the focus of a continuous wave (cw)-laser across the retina of Dutch belted rabbits, producing microsecond irradiation at each RPE cell. Two irradiation patterns forming separated lines (SEP) or interlaced lines (INT), different dwell times (2.5-75 μs), and repetition numbers (10 and 100 scans with 100-Hz repetition rate) were tested. Thresholds were evaluated by fundus imaging and angiography. Histology was performed for selected parameters. RESULTS. Selective RPE cell damage was obtained with moderate laser power. The angiographic threshold power decreased with pulse duration, number of exposures, and applying the INT pattern. Ophthalmoscopic thresholds, indicating onset of thermal coagulation, were higher than twice the angiographic threshold for most tested parameters. Histology confirmed selective RPE cell damage for SEP irradiation with 7.5 and 15 μs; slower scan speeds or closed lines caused photoreceptor damage. CONCLUSIONS. A cw-laser scanner can be set up as a highly compact and versatile device. Selective RPE damage is feasible with dwell times up to 15 μs. Greatest selectivity is achieved with short exposure times and separated scan lines. Interlaced lines and long exposure times facilitate heat conduction into photoreceptors. A scanner is an attractive alternative for pulsed selective targeting, because both selective targeting and thermal photocoagulation can be realized.

Original languageEnglish
JournalInvestigative Ophthalmology and Visual Science
Issue number4
Pages (from-to)1782-1792
Number of pages11
Publication statusPublished - 04.2007

Research Areas and Centers

  • Academic Focus: Biomedical Engineering


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