Effects of selective retina therapy on retinal oxygen saturation compared to conventional photocoagulation in rabbits

Purpose Subvisible selective retina therapy (SRT) was designed to target retinal pigment epithelium (RPE) without damaging adjacent photoreceptors. This study evaluated the changes in retinal oxygen saturation and retina histology after SRT compared to conventional photocoagulation(PC) in rabbits. Methods One eye in each of 10 chinchilla bastard rabbits was treated with 144 spots of SRT (527 nm) or conventional laser treatment (577 nm), respectively. After treatment, fundus photography, optical coherence tomography, and fluorescein angiography were performed to detect lesions. At 1 week post‐treatment, retinal oxygen saturation in untreated, SRT‐treated, and PC‐treated areas was evaluated in five eyes. Histologic evaluation was performed using light and electronic microscopy. At 4 weeks post‐treatment, the same procedures were performed in the remaining five eyes. Results At 1 week post‐treatment, mean retinal oxygen saturation in the PC‐treated area (23.3 ± 7.2 mm Hg) was relatively higher than in the untreated (16.6 ± 4.3) and SRT (15.34 ± 5.3) areas. Similar results were found at 4 weeks post‐treatment (PC‐treated, 25.3 ± 8.5; untreated, 14.4 ± 5.2, SRT‐treated, 15.2 ± 4.6). OCT and histological examinations revealed selective RPE damage while sparing photoreceptors in the SRT lesion. In contrast, broad damage in multiple retinal layers including the photoreceptors was observed in conventional PC lesions. Conclusions Increased retinal oxygen saturation after conventional PC might be due to widespread destruction of retinal layers including photoreceptors which is most oxygen consuming structure in retina. In contrast, relatively unchanged retinal oxygen saturation was observed in SRT lesions with intact retinal layers and photoreceptors. SRT can be used as an photoreceptor saving laser therapy in RPE dysfunction diseases such as DME or CSC.