Retinal vascular oxygen saturation in response to a less extensive laser treatment in proliferative diabetic retinopathy

Purpose: The purpose of this study was to evaluate the association between retinal laser burden and vascular oxygen saturation in patients with proliferative diabetic retinopathy (PDR) treated with different extent of retinal laser. Methods: The study was a prospective, interventional study of patients with treatment-naïve PDR. Patients were treated with navigated retinal laser (Navilas^®, OD-OS GmbH, Teltow, Germany) in different doses. Retinal oximetry was obtained at baseline (BL) prior to laser and after 6 months (M6). Patients were divided into three groups according to total laser spots applied: <1500 spots (Group 1), 1500–2000 spots (Group 2), and >2000 spots (Group 3). Results: We included 33 eyes of 28 patients with treatment-naïve PDR. The groups did not differ according in BL characteristics. Between BL and M6, retinal arteriolar oxygen saturation did not change but retinal venular oxygen saturation (median with interquartile range) decreased in Groups 1 and 2 (1: 65.5 ± 8.8% versus 60.5 ± 9.5%, p = 0.04; 2: 65.3 ± 7.3% versus 63.0 ± 13.5%, p = 0.04). Focal retinal venular oxygen saturation, located to quadrants with retinal neovascularization, decreased in Group 2 from BL to M6 (67.5 ± 13.3% versus 61.5 ± 8.8%, p = 0.04). Retinal venular diameter decreased from BL to M6 in Group 1 (174.5 ± 15.3 μm versus 165.1 ± 28.7 μm, p = 0.01). Conclusions: In this study of patients with treatment-naïve PDR, we showed that a less extensive laser treatment caused a reduction in retinal venular oxygen saturation and diameter 6 months after treatment. Our results suggest that less extensive laser treatment may be sufficient to improve the retinal metabolic environment conducive to PDR regression.