Special Section on Photoacoustic Imaging and Sensing

Automatic temperature controlled retinal photocoagulation

[+] Author Affiliations
Kerstin Schlott

University of Lübeck, Institute of Biomedical Optics, Peter-Monnik-Weg 4, D-23562, Lübeck, Germany

Stefan Koinzer, Johann Roider

University Medical Center of Schleswig-Holstein, Department of Ophthalmology, Kiel, Germany

Lars Ptaszynski, Marco Bever, Alex Baade

Medical Laser Center Lübeck, Lübeck, Germany

Reginald Birngruber, Ralf Brinkmann

University of Lübeck, Institute of Biomedical Optics, Peter-Monnik-Weg 4, D-23562, Lübeck, Germany

Medical Laser Center Lübeck, Lübeck, Germany

J. Biomed. Opt. 17(6), 061223 (May 07, 2012). doi:10.1117/1.JBO.17.6.061223
History: Received September 15, 2011; Revised March 23, 2012; Accepted March 29, 2012
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Abstract.  Laser coagulation is a treatment method for many retinal diseases. Due to variations in fundus pigmentation and light scattering inside the eye globe, different lesion strengths are often achieved. The aim of this work is to realize an automatic feedback algorithm to generate desired lesion strengths by controlling the retinal temperature increase with the irradiation time. Optoacoustics afford non-invasive retinal temperature monitoring during laser treatment. A 75ns/523nm Q-switched Nd:YLF laser was used to excite the temperature-dependent pressure amplitudes, which were detected at the cornea by an ultrasonic transducer embedded in a contact lens. A 532 nm continuous wave Nd:YAG laser served for photocoagulation. The ED50 temperatures, for which the probability of ophthalmoscopically visible lesions after one hour in vivo in rabbits was 50%, varied from 63°C for 20 ms to 49°C for 400 ms. Arrhenius parameters were extracted as ΔE=273Jmol1 and A=3·1044s1. Control algorithms for mild and strong lesions were developed, which led to average lesion diameters of 162±34μm and 189±34μm, respectively. It could be demonstrated that the sizes of the automatically controlled lesions were widely independent of the treatment laser power and the retinal pigmentation.

Figures in this Article
© 2012 Society of Photo-Optical Instrumentation Engineers

Topics

Lasers ; Eye ; Tissues

Citation

Kerstin Schlott ; Stefan Koinzer ; Lars Ptaszynski ; Marco Bever ; Alex Baade, et al.
"Automatic temperature controlled retinal photocoagulation", J. Biomed. Opt. 17(6), 061223 (May 07, 2012). ; http://dx.doi.org/10.1117/1.JBO.17.6.061223


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