Abstract
Purpose :
Selective retina therapy (SRT) intends to selectively initiate immediate cell disruption of dysfunctional or senescent patches of the retinal pigment epithelium (RPE) monolayer without scarring the choroid and neurosensory retina, and especially sparing non-regenerative photoreceptor (PR) inner segments. In this experiment, a novel, high-power (30 W) continous-wave (CW) photocoagulation laser was used for pulsed RPE irradiation.
Methods :
Pigmented rabbit eyes were exposed to laser pulses of 8 μs in duration (wavelength: 532 nm; retinal spot size: 223 × 223μm2) using the research device Spectralis Centaurus (HuCEoptoLab, Bern University of Applied Sciences, Biel, CH). This device is based on a modified diagnostic imaging platform (Spectralis, Heidelberg Engineering, Heidelberg, DE), extended with a prototype treatment laser (modified Merilas 532 shortpulse, Meridian Medical, Thun, CH) intended for SRT. Post-irradiation retinal changes were assessed with fluorescein angiography (FA), indocyanine green angiography (ICGA), and optical coherence tomography (OCT). Following euthanization 6 hours after laser exposure, two eyes of one animal were processed for histology, sectioned in 1 μm sections stained with toluidin blue for light microscopy (LM) evaluation and sectioned in 75 nm for transmission electron microscopy (TEM) evaluation.
Results :
FA and ICGA immediately after SRT irradiation demonstrated hyperfluorescent changes in the area of the intended RPE damage, whereas no morphologic tissue change was visible in OCT. LM and TEM showed that RPE cell membranes had ruptured and microvacuoles had formed. PR outer segments showed an elongation but without signs for morphological membrane and disk damage. Furthermore, an intact Bruch's membrane was found in the SRT irradiated areas.
Conclusions :
For the first time, a pulsed high-power CW-photocoagulation laser provided evidence for selective RPE disruption in rabbits in vivo using short pulses of 8 μs duration. This result is consistent with previous experiments on selective RPE cell destruction with short microsecond pulses using Q-switched lasers and scanning CW-lasers. The novel laser can therefore be used for SRT and at the same time fulfills all treatment parameters between SRT and photocoagulation, making this laser very versatile for retinal laser treatments.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.