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Journal of Biomedical Optics

Automatic temperature controlled retinal photocoagulation
Author(s): Kerstin Schlott; Reginald Birngruber; Ralf Brinkmann; Stefan Koinzer; Johann Roider; Lars Ptaszynski; Marco Bever; Alexander Baade
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Paper 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 75  ns/523  nm 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 = 273  J mol−1 and A = 3·1044  s−1. Control algorithms for mild and strong lesions were developed, which led to average lesion diameters of 162±34  μm and 189±34  μm, 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.

Paper Details

Date Published: 7 May 2012
PDF: 9 pages
J. Biomed. Opt. 17(6) 061223 doi: 10.1117/1.JBO.17.6.061223
Published in: Journal of Biomedical Optics Volume 17, Issue 6
Show Author Affiliations
Kerstin Schlott, Univ. zu Lübeck (Germany)
Reginald Birngruber, Univ. zu Lübeck (Germany)
Ralf Brinkmann, Univ. zu Lübeck (Germany)
Stefan Koinzer, Univ. Schleswig-Holstein (Germany)
Johann Roider, Univ. Schleswig-Holstein (Germany)
Lars Ptaszynski, Medizinisches Laserzentrum Lübeck GmbH (Germany)
Marco Bever, Medizinisches Laserzentrum Lübeck GmbH (Germany)
Alexander Baade, Medizinisches Laserzentrum Lübeck GmbH (Germany)

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