Non-invasive optoacoustic temperature determination during retinal cw-laser treatments

Jochen Kandulla*, Hanno Elsner, Julien Sandeau, Reginald Birngruber, Ralf Brinkmann

*Corresponding author for this work


In almost all retinal laser treatments the therapeutic effect is initiated by a transient temperature increase. Due to differences in tissue properties and physiology like pigmentation and vascular blood flow an individually different temperature increase might occur with crucial effects on the therapeutic benefit of the treatment. In order to determine the individual retinal temperature increase during cw-laser irradiation in real-time we developed a non-invasive method based on optoacoustics. Simultaneously to the cw-laser irradiation (λ = 810 nm, P < 3 W, t = 60 s) pulses from a dye laser (λ = 500 nm, τ = 3.5 ns, E ≈ 5 μJ) are applied concentrically to the cw-laser spot on the eyeground. The absorption of the pulses lead to a consequent heating and thermoelastic expansion of the tissue. This causes the emission of an ultrasonic pressure wave, which amplitude was found to be temperature dependent following in good approximation a 2nd order polynomial. The pressure wave was measured by an ultrasonic transducer embedded in a contact lens placed on the cornea. The experiments were performed in-vivo on rabbits. Simultaneous measurements with a miniaturized thermocouple showed a similar slope with a maximum local deviation of 0.4 °C for a temperature increase of 5.5 °C. On two rabbits measurements pre and post mortem at the same location were performed. The temperature increase after 60 s was found to raise by 12.0 % and 66.7 % post mortem, respectively. These data were used to calculate the influence of heat convection by blood circulation using a numerical model based on two absorbing layers and assuming a constant perfusion rate for the choriocapillaris and the choroid. Overall the presented optoacoustic method seems feasible for a non-invasive real-time determination of cw-laser induced retinal temperature increases and might serve as a temperature based dosimetry control during retinal laser treatments.

Original languageEnglish
Title of host publicationOphthalmic Technologies XVI
EditorsFabrice Manns, Per G. Söderberg, Arthur Ho
Number of pages8
Publication date07.03.2006
Article number61381H
ISBN (Print)978-081946181-0
Publication statusPublished - 07.03.2006
EventOphthalmic Technologies XVI - San Jose, United States
Duration: 21.01.200624.01.2006
Conference number: 67565

Research Areas and Centers

  • Academic Focus: Biomedical Engineering


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