Measurement of the circulation in patients with diabetes mellitus and establish a link between retinal venous pressure (RVP) and endothelin (ET-1)levels.

Diabetic retinopathy and maculopathy are the main causes of visual loss. Hyperglycemia as the main risk factor of diabetic retinopathy induced damage to retinal capillaries. These in turn lead to hypoxia in the tissue and promote the release of VEGF (vascular endothelial growth factor) , which in turn increases the vascular pathology. Simultaneously, there is an increased expression of endothelin (ET-1). Endothelin increases vascular tone and regulates the micro-and macro-vascular remodeling.

In ocular blood flow perfusion pressure plays an important role. While in healthy eyes a spontaneous retinal venous pulsation is frequently observed, this is significantly less frequent in diseased eyes. An increased venous pressure lowers the ocular perfusion pressure, and increases the transmural pressure. A measurement of the retinal venous pressure and the hormone ET-1 in the blood will give us a better knowledge of the circulatory changes and their relationship to diabetes.

Inclusion Criteria:

• diabetes mellitus type I or II
• no diabetic retinopathy

Exclusion Criteria:

• known diabetic retinopathy
• acute or chronic inflammation of the eyes
• narrow angle glaucoma
• minority

Patients with diabets mellitus type I or II, without diabetic retinopathy