Abstract
Purpose :
We have previously reported on a personal computer (PC) based real-time temperature-guided retinal laser system to improve reproducibility in retinal effects, especially in subvisible laser therapy. This method and technique has proven effective in laboratory setups for preclinical tests. In order to introduce the system clinically and comply with regulatory requirements, the system was fully integrated to a microcontroller-based system and evaluated on rabbits in this study.
Methods :
The microcontroller-based module is optically coupled between the treatment laser system (Zeiss VisuLas 532s) and the slitlamp. It uses a probe laser with a frequency of 3 kHz to measure the temperature. Further it modulates the treatment laser power based on a temperature feedback loop. The power is adjusted so that a preset target-temperature is held nearly constant over the overall irradiation time of 100ms.
6 eyes of 3 rabbits were irradiated, overall 279 spots with a diameter of 200 µm were applied and analyzed. Target temperatures from 45 to 69 °C in steps of 3 °C were addressed. After 1 hour, the eyes were examined with fluorescein angiography (FAG), color fundus photography (CFP) and optical coherence tomography (OCT). Visibility thresholds were calculated with probit analysis in R, a pseudo-coefficient of determination R2 was calculated with the McFadden method.
Results :
The microcontroller system was able to reliably reproduce results of the PC-based laboratory system, the following ED-50 values could be determined: 61° C for direct funduscopic visibility, 58°C for visibility after 1 hour, 55°C for OCT, 56° for FAG. All probit analyses for ED-50 determination showed better correlation to temperature than to laser power (funduscopic visibility R2 = 0.63 vs. R2 = 0.48, others similar).
Conclusions :
We could show that with active controlled real-time power modulation a preset target temperature can reliably be address, which compensates for absorption difference at the fundus demonstrated by the lower R2 for the laser power. Subsequently, this microcontroller system is currently evaluated in a first clinical pilot study.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.