27 September 2016 Lesion strength control by automatic temperature guided retinal photocoagulation
Author Affiliations +
J. of Biomedical Optics, 21(9), 098001 (2016). doi:10.1117/1.JBO.21.9.098001
Laser photocoagulation is an established treatment for a variety of retinal diseases. However, when using the same irradiation parameter, the size and strength of the lesions are unpredictable due to unknown inter- and intraindividual optical properties of the fundus layers. The aim of this work is to investigate a feedback system to generate desired lesions of preselectable strengths by automatically controlling the irradiation time. Optoacoustics were used for retinal temperature monitoring. A 532-nm continuous wave Nd:YAG laser was used for photocoagulation. A 75-ns/523-nm Q-switched Nd:YLF laser simultaneously excited temperature-dependent pressure transients, which were detected at the cornea by an ultrasonic transducer embedded in a contact lens. The temperature data were analyzed during the irradiation by a LabVIEW routine. The treatment laser was switched off automatically when the required lesion strength was achieved. Five different feedback control algorithms for different lesion sizes were developed and tested on rabbits in vivo. With a laser spot diameter of 133  μm, five different lesion types with ophthalmoscopically visible diameters ranging mostly between 100 and 200  μm, and different appearances were achieved by automatic exposure time control. The automatically controlled lesions were widely independent of the treatment laser power and the retinal pigmentation.
© 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
Kerstin Schlott, Stefan Koinzer, Alexander Baade, Reginald Birngruber, Johann Roider, Ralf Brinkmann, "Lesion strength control by automatic temperature guided retinal photocoagulation," Journal of Biomedical Optics 21(9), 098001 (27 September 2016). https://doi.org/10.1117/1.JBO.21.9.098001

Automatic control

Laser coagulation

Temperature metrology


Laser therapeutics


Laser damage threshold

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