Medical Laser Center Lübeck, Lübeck, Germany.
Department of Ophthalmology, University of Lübeck, Lübeck, Germany.
Invest Ophthalmol Vis Sci. 2021 Mar 1;62(3):32. doi: 10.1167/iovs.62.3.32.
New lasers with a continuous wave power exceeding 15 W are currently investigated for retinal therapies, promising highly localized effects at and close to the Retinal Pigment Epithelium (RPE). The goal of this work is to evaluate mechanisms and thresholds for RPE cell damage by means of pulse durations up to 50 µs.
A diode laser with a wavelength of 514 nm, a power of 15 W, and adjustable pulse durations between 2 µs and 50 µs was used. Porcine RPE-choroidal explants (ex vivo) and chinchilla bastard rabbits (in vivo) were irradiated to determine threshold radiant exposures for RPE damage ({\bar H_{Cell}}) by calcein vitality staining and fluorescence angiography, respectively. Thresholds for microbubble formation (MBF) ({\bar H_{MBF}}) were evaluated by time-resolved optoacoustics. Exemplary histologies support the findings.
({\bar H_{{{MBF}}}}) is significantly higher than ({\bar H_{Cell}}) at pulse durations ≥ 5 µs (P < 0.05) ex vivo, while at 2 µs, no statistically significant difference was found. The ratios between ({\bar H_{{{MBF}}}}) and ({\bar H_{Cell}}) increase with pulse duration from 1.07 to 1.48 ex vivo and 1.1 to 1.6 in vivo, for 5.2 and 50 µs.
Cellular damage with and without MBF related disintegration are both present and very likely to play a role for pulse durations ≥ 5 µs. With the lower µs pulses, selective RPE disruption might be possible, while higher values allow achieving spatially limited thermal effects without MBF. However, both modi require a very accurate real-time dosing control in order to avoid extended retinal disintegration in this power range.
目前正在研究具有超过 15 W 连续波功率的新型激光器，用于视网膜治疗，有望在视网膜色素上皮（RPE）及其附近实现高度局域化的效果。这项工作的目的是通过长达 50 μs 的脉冲持续时间来评估 RPE 细胞损伤的机制和阈值。
使用波长为 514nm、功率为 15W 且脉冲持续时间可调范围为 2 μs 至 50 μs 的二极管激光器。对猪 RPE-脉络膜外植体（离体）和智利兔杂种兔（体内）进行辐照，通过 calcein 活力染色和荧光血管造影分别确定 RPE 损伤的阈值辐射暴露量({\bar H_{Cell}})。通过时间分辨光声法评估微泡形成（MBF）阈值({\bar H_{MBF}})。举例说明的组织学支持这些发现。
在脉冲持续时间≥5 μs 时（P < 0.05），({\bar H_{{{MBF}}}})明显高于({\bar H_{Cell}})，而在 2 μs 时，未发现统计学上的显著差异。在离体情况下，从 5.2 μs 到 50 μs，({\bar H_{{{MBF}}}})与({\bar H_{Cell}})之间的比值从 1.07 增加到 1.48；在体内情况下，该比值从 1.1 增加到 1.6。
在脉冲持续时间≥5 μs 时，存在与微泡相关的细胞破坏和无微泡相关的细胞破坏，这两种情况都很可能起作用。对于较低的 μs 脉冲，可能可以选择性地破坏 RPE，而较高的数值允许在没有微泡的情况下实现空间上有限的热效应。然而，这两种模式都需要非常精确的实时剂量控制，以避免在该功率范围内对视网膜造成扩展破坏。
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