Abstract
Purpose :
The adequate dosing of laser power for uniform, non-damaging and only thermally stimulating therapy is very challenging, as the absorptions at the retinal pigment epithelium (RPE) and choroid vary greatly across the fundus. Therefore, commonly used titration lesions at the vascular arcades are not an accurate method. The aim of our approach is an automatically temperature-controlled laser therapy for each individual irradiation spot using optoacoustics. The physician only has to enter the desired temperature increase and, for safety reasons, the maximum power of the therapy laser.
Methods :
10 chronic CSCR patients with subretinal fluid and a single angiographic leakage site are included in the study. A 532 nm cw laser (Zeiss VisuLas 532) was used for treatment with a duration of 100 ms per 200 μm spot. A separate control module (Medical Laser Center Lübeck) is coupled between the therapy laser and the slitlamp and controls the laser power with a frequency of 3 kHz. Prior to irradiation in the target area, test irradiations are carried out with different target temperatures in order to correlate the funduscopic visibility threshold to the temperature rise. Six central treatment spots are then performed around the leakage site with half of this temperature rise. After irradiation, color fundus photography (CFP) and optical coherence tomography (OCT) are performed.
Results :
8 patients were treated so far. In all patients the immediate funduscopic visibility threshold was found at 65 °C. After one hour, spots with 60 °C were also faintly visible. Comparable to prior animal experiments, the respective target temperatures were also reached and maintained within 50 ms and kept constant thereafter. All therapeutic irradiations at the central leakage area were performed at 51 °C. These spots remained invisible in CFP and OCT. The average laser power per spot for the target temperature of 51 °C varied between 35 and 94 mW. In most patients the subretinal fluid was resolved so far, statistic analysis of all results will be reported after study completion.
Conclusions :
It is clinically demonstrated that automatic temperature-controlled laser therapy can be performed safely and reproducibly in CSCR patients. The wide range of laser powers shows the necessity of active real-time temperature control to achieve uniform thermal effects and to accurately guide invisible non-damaging laser irradiation.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.