Changes in retinal venular oxygen saturation predict activity of proliferative diabetic retinopathy 3 months after panretinal photocoagulation

BACKGROUND/AIMS: Proliferative diabetic retinopathy (PDR) is a severe blinding condition. We investigated whether retinal metabolism, measured by retinal oximetry, may predict PDR activity after panretinal laser photocoagulation (PRP). METHODS: We performed a prospective, interventional, clinical study of patients with treatment-naive PDR. Wide-field fluorescein angiography (OPTOS, Optomap) and global and focal retinal oximetry (Oxymap T1) were performed at baseline (BL), and 3 months (3M) after PRP. Angiographic findings were used to divide patients according to progression or non-progression of PDR after PRP. We evaluated differences in global and focal retinal oxygen saturation between patients with and without progression of PDR after PRP treatment. RESULTS: We included 45 eyes of 37 patients (median age and duration of diabetes were 51.6 and 20 years). Eyes with progression of PDR developed a higher retinal venous oxygen saturation than eyes with non-progression at 3M (global: +5.9% (95% CI –1.5 to 12.9), focal: +5.4%, (95% CI –4.1 to 14.8)). Likewise, progression of PDR was associated with a lower arteriovenular (AV) oxygen difference between BL and 3M (global: –6.1%, (95% CI –13.4 to –1.4), focal: –4.5% (95% CI –12.1 to 3.2)). In a multiple logistic regression model, increment in global retinal venular oxygen saturation (OR 1.30 per 1%-point increment, p=0.017) and decrement in AV oxygen saturation difference (OR 0.72 per 1%-point increment, p=0.016) at 3M independently predicted progression of PDR. CONCLUSION: Development of higher retinal venular and lower AV global oxygen saturation independently predicts progression of PDR despite standard PRP and might be a potential non-invasive marker of angiogenic disease activity.