Time resolved detection of tissue denaturation during retinal photocoagulation

Kerstin Schlott*, Jens Langejürgen, Marco Bever, Stefan Koinzer, Reginald Birngruber, Ralf Brinkmann

*Corresponding author for this work


The retinal photocoagulation is an established treatment method for different retinal diseases. The extent of the thermal coagulations depends strongly on the generated temperature increase. Until now the dosage is based on a pool of experience of the treating physicians as well as the appearance of the whitish lesions on the retina. The temperature course during photocoagulation can be measured in real-time by optoacoustics. A frequency-doubled Q-switched Nd:YLF laser (523nm, 75 ns) is used for optoacoustic excitation and a continuous-wave Nd:YAG laser (532nm) with adjustable irradiation time and power for heating of the fundus tissue. The onset of coagulation is determined by a photodiode that is placed directly behind enucleated porcine eyes, which served as a model. The onset of coagulation is observed clearly when scattering sets in. The required power for coagulation increases exponentially with decreasing irradiation time. The first results on rabbit eyes in vivo indicate that the onset of coagulation defined by just barely visibile lesions at a slit lamp sets in at an ED50 threshold temperature of 63°C for an irradiation time of 400 ms. In conclusion, optoacoustics can be used to determine temperatures during retinal laser treatments in real-time. This allows evaluating the time-temperature-dependence of retinal coagulation in vivo.

Original languageEnglish
Number of pages8
Publication statusPublished - 17.07.2009
EventEuropean Conference on Biomedical Optics 2009 - Munich, Germany
Duration: 14.06.200918.06.2009
Conference number: 104337


ConferenceEuropean Conference on Biomedical Optics 2009
Abbreviated titleECBO 2009

Research Areas and Centers

  • Academic Focus: Biomedical Engineering


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