Power-controlled temperature guided retinal photocoagulation

Alexander Baade, Wadim Schwarzer, Stefan Koinzer, Kerstin Schlott, Reginald Birngruber, Ralf Brinkmann


The necessary lesion strength for a given therapeutical effect in retinal photocoagulationis is currently the subject of several investigations. In some cases, even sub-visible irradiations can be beneficial for the patient. The aim of this work is to realise an automatic temperature feedback algorithm to perform uniform sub-visible and visible irradiations with a total irradiation time of 50 ms. A 75 ns/523 nm Q-switched Nd:YLF laser is used to induce optoacoustic temperature-dependent pressure amplitudes at the retina, which are detected at the cornea by an ultrasonic transducer embedded in a contact lens. A 532 nm continuous wave Nd:YAG laser serves as treatment laser and the power was adjusted during the irradiation in order to achieve the desired temperature rise. The feedback algorithm was applied for four aim temperatures, 50, 57, 65 and 82 °C. The results showed ophthalmoscopically or angiographically invisible effects for irradiations at 50 °C, despite a wide range of treatment powers. The standard deviation for the achieved temperatures ranged from 3.0 °C for an aim temperature of 50 °C to 8.8 °C for 82 °C. The introduced method could be used to improve photocoagulation for shorttime irradiations and allow the investigation of sub-visible effects.
Original languageEnglish
Title of host publicationOphthalmic Technologies XXV
EditorsFabrice Manns, Per G. Söderberg, Arthur Ho
Number of pages10
Publication date20.03.2015
ISBN (Print)9781628413977
Publication statusPublished - 20.03.2015
EventSPIE BIOS - San Francisco, United States
Duration: 07.02.201512.02.2015


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