Debate continues: Gastric bypass surgery does not increase the risk for sight-threatening diabetic retinopathy.

Abstract

I read with great interest the article by Morén et al. (2018) with reference to their research on ‘Gastric bypass surgery does not increase the risk for sight-threatening diabetic retinopathy’. I thank them for their important contribution in clarifying an enigmatic disease complex that was lacking definitive data and that had insufficient guidelines for treatment and follow-up. The authors investigated the occurrence and level of diabetic retinopathy (DRP) before and after planned bariatric surgery and the potential risk factors for deterioration of DRP. However, of the 117 patients in this study, the total number of the eyes with severe non-proliferative DRP and proliferative DRP were lower than 2% (two patients). This means that there were almost no patients with serious diabetic eye disease. However, a previous study (Murphy et al. 2015) reported that higher preoperative DRP grade is an independent risk factor for the progression of DRP following bariatric surgery. On the other hand, the present study reported a significant reduction of glycated haemoglobin (HbA1c) levels, and there is a known paradoxical relationship between the rapid reduction in HbA1c and exacerbated DRP (Brinchmann-Hansen et al. 1985). I would like to ask the researchers, do they think that having a low-grade DRP population is the reason for these results? Nutrient deficiency is another problem related to bariatric surgery, and a recent study reported (Kikkas et al. 2018) a cumulative ferritin deficiency in 47% of the patients. Iron deficiency is a very old phenomenon that is accused of being a risk factor for the progression of DRP (Shorb 1985). I would like to ask the researchers if they had any patients with iron deficiency or another nutritional deficiency such as B12? To sum up, I believe that further studies will reveal new aspects on DRP and its relation to bariatric surgery not only for mild to moderate diseases but also for serious DRP. However, with the current knowledge available, we still have to be careful of the consequences.