Purpose: Low-energy red laser irradiation has been rapidly promoted for clinical use in the prevention and control of myopia in adolescents. However, the safety of this technique's dosage needs further investigation. This study aims to explore the acute pathological characteristics of retinal structural and functional damage induced by supra-dose 650 nm diode red laser irradiation using a pigmented rabbit model.
Methods: 16 eyes from 8 pigmented rabbits were studied, the rabbits were randomly divided into three groups: Experimental group: Right-eye irradiation (n=6); self-control group: Left-eye self-control (n=6); blank control group: No irradiation (n=4). The experimental group received 3 minutes of 650 nm red laser irradiation (20 mW, diode laser lamp) on the right eye of 6 rabbits, while their left eyes served as self-controls. The blank control group consisted of 2 rabbits (4 eyes) with no irradiation. Using optical coherence tomography (OCT) to evaluate retinal structure before irradiation. Changes in the retinal structure and function of the irradiated eyes were observed using electroretinography (ERG) and OCT. Apoptosis of retinal cells was examined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Expression of p53 and caspase 3 in retinal tissue was measured using immunofluorescence. These assessments were used to analyze the acute damage characteristics of the retina following supra-dosage 650 nm diode red laser irradiation.
Results: After a 3-minute-irradiation with 20 mW red light, ERG results demonstrated significant delays in b-wavećOPS-wave latency (p < 0.05) and a reduction in amplitude (p < 0.05) for the irradiated eyes under dark adaptation. A significant decrease in a-wave amplitude (p < 0.05) was observed under dark adaptation. The analysis of OCT results revealed that the structure of the retina in the irradiated eye was disrupted, characterized by outer retinal layer edema, disruption of the retinal pigment epithelium, and increased reflectivity in the inner retina. More TUNEL-positive apoptotic cells were observed in the outer nuclear layer of the retinal tissue in the experimental group. Higher expression levels of p53 and caspase 3 were detected in the outer nuclear layer of the retinal tissue.
Conclusions: Short-term exposure to supra-threshold red light induces structural disorganization of the retina and compromises retinal electrophysiological function in rabbits. Further investigation into the safety implications of red light therapy is warranted to ensure its clinical applicability.