Quantification of Rising the Osmotic Pressure in Diabetic Intraretinal Fluid Accumulation (Diabetic Macular Oedema)

Diabetic macular oedema is characterized by fluid accumulation in the retinal tissue from leaking retinal vessels, the capillaries. This state can lead to severe visual loss and blindness. According to basic physiologic rules several factors influence the fluid transport between the capillaries and the surrounding tissue. One of these factors is the balance between the large molecules within the vessel lumen and the retinal tissue. Some drugs change this balance, the osmotic balance, by moving the fluid from the tissue to the vessel lumen. In relation to diabetic macular oedema, treatment with such a drug potentially would reduce the retinal thickness because it extracts fluid from the retinal tissue. Glycerol has this potential. If reduction of the thickness with glycerol is confirmed, then it proves the significance of the osmotic balance in the basic nature of diabetic macular oedema. In this study we therefore examine the time dependent change in retinal thickness after glycerol intake by an instrument called optical coherence tomography (OCT). The participants drink glycerol and the thickness of the retina is then monitored closely by OCT during the following three hours. Since diabetic changes in the retina are focal pr. definition, the secondary purpose of the study is to find any regional differences in the response. The examinations are repeated at a second visit where the patient drink another dose of glycerol, because we also want to analyse for a dose dependent response. Which dose is given at each visit is randomised on beforehand. In addition to measuring the retinal thickness a variety of examinations are performed both before and during the study, e.g. blood samples and systemic blood pressure measurements.