## 2 Materials and Methods  
### Treatment and Monitoring System  
The so-called Spectralis Centaurus system (HuCE-optoLab, Bern University of Applied Sciences, Biel, CH) was used for the experiments. It consists of an opto-mechanically upgraded commercial diagnostic imaging platform (SPECTRALIS HRA+OCT, Heidelberg Engineering, Heidelberg, DE) and is extended with an experimental SRT laser (modified MERILAS 532 shortpulse, Meridian, Thun, CH). The system utilizes SD-OCT as widely used for diagnosis of retinal diseases by capturing cross-sectional and volumetric images (B- and C-scans). It features the ability of intervention planning via a coaxially integrated confocal scanning laser ophthalmoscope (cSLO). Furthermore, it can be operated in the so-called M-scan mode (motion mode) to measure time-resolved sequences of A-scans at the point of the therapy laser application, thereby revealing depth-resolved temporal signal fluctuations, e.g., tissue movements during laser exposure (Figure 1). The experimental SRT laser utilizes optically pumped semiconductor laser (OPSL) technology and emits light at 532 nm wavelength, with a peak power of 30 W. It can be operated in two different modes: CW mode and SRT mode. In CW mode, the laser operates like a conventional LPC laser, which was used to create marker lesions on the sample. Figure 1: Setup and functionality of the Spectralis Centaurus system: Treatment laser (532 nm) and SD-OCT (870 nm) path are combined by a dichroic mirror (black-dashed rectangle). Retina scanning is performed by a galvanometric scanner. A chromatically corrected objective focuses the collinear treatment and OCT laser beams. The reflected light is separately guided towards the spectrometer and a fast diode. The fast scanning IR cSLO (820 nm) eases treatment planning by displaying a fundus image + where the treatment pattern can be placed interactively. The porcine RPE-choroid-sclera explants were mounted in an upright artificial eye (optical power: 65 dpt). In SRT mode, the laser emits single pulses or bursts of laser pulses of 2 to 20 \(\upmu\)s pulse duration at a repetition rate of 100 Hz. The laser radiation is transmitted via a square core multimode fiber into the camera head of the system, to laterally homogenize the beam profile, where it is combined with the OCT laser beam by a dichroic mirror as depicted in Figure 1. The projected top-hat square beam profile measured 120 \(\times\) 120 \(\upmu\)m\({}^{2}\) on the RPE-choroid-sclera explant's surface. Prior to the tissue experiments, the top-hat square beam profile was rated regarding its spatial intensity modulation factor (IMF). The IMF describes the ratio of maximum to mean radiant exposure over the beam profile and was first introduced by [PERSON] et al. in 2002 as a speckle factor [31]. IMF = 1 corresponds to perfectly homogenous, top-hat radiant exposure. To calculate the IMF, the treatment laser beam was imaged with a magnification of 9.81 onto a beam analyzer camera (BC 106 VIS, Thorlabs Inc., Newton, NJ, USA)) behind the laser aperture of the system. An IMF = 1.3 was determined, which indicates a high-quality top-hat beam profile [32]. The diagnostic imaging part of the system is based on spectral-domain (SD), also called Fourier-domain (FD) OCT, which allows high-speed and high-resolution imaging of the retina with an interferometric high-speed spectrometer, enabling simultaneous acquisition of a depth or amplitude mode (A) scan. The super-luminescence diode of the SD-OCT laser emits infrared radiation centered at 870 nm wavelength and 73 nm (840-913 nm) spectral bandwidth. The OCT system is operated at a rate of 33 kHz and 30.3 \(\upmu\)s per A-scan integration time. In B-scan mode, the beam scans across the retina, producing a cross-sectional image. For volumetric, three-dimensional retinal imaging (C-scan), up to 768 orthogonally equally spaced B-scans are acquired sequentially.