Real-time temperature-control for cw retinal laser therapy in a clinical study

Objective dose control is currently not possible for laser treatments at the retina. Especially in the case of subvisible irradiations, the assessment of the intended temperature effects by the visual control of the doctors is impossible. Due to the large individual differences in light transmission of the eye and absorption at the RPE, for the same laser power the achieved temperature varies at the RPE. Therefore, an opto acoustic technique to measure the temperature of the retina during laser treatment was developed and applied in a clinical study. A conventional 532 nm cw laser was used during a standard treatment. A microcontroller-based control module was optically coupled between the treatment laser and the slit lamp. This control module is able to measure and automatically control the RPE temperature rise in real time at a rate of 3 kHz and regulates the laser power in such a way that a target temperature specified by the physician is reached within several ms and kept constant until the end of the irradiation time of 100 ms. In the clinical study on patients with CSCR, a target temperature of 51°C was set. So far 7 Patients were treated. Target temperature could be reached and kept constant until the end of irradiation time of 100 ms. A wide range of applied laser power (35 to 95 mW) was used and show the need for active control during retinal laser treatment. It was demonstrated that temperature-controlled retinal laser therapy can be applied safely in patients.