The purpose of this study is to compare the effect of two antihypertensive drugs on retinal vessel diameter in young type 1 diabetics. The retinal vessel analyzer (RVA) was used to investigate how the drugs affected vessel diameter, when the subjects were exposed to an increase in blood pressure, induced by isometric muscle contraction and when they were stimulated by flickering light.

Diabetes is a leading cause of blindness in the western part of the world. Diabetic patients develop diabetic retinopathy which can progress to blindness. Diabetic retinopathy is associated with an increase of blood flow in the retinal vessels, ischaemia in the periphery and macular oedema. It has been shown in previous trials, that the pressure and metabolic autoregulation is disturbed in patients with diabetes, and it is believed to contribute to the development of diabetic retinopathy.

In healthy subjects the retinal arterioles will contract during an increase in blood pressure, but trials have shown that this response is impaired in diabetics. When the retina is exposed to flickering lights, the metabolism increase and the arterioles in healthy subjects dilates. In diabetics this dilation is impaired. In this trial we want to investigate if an ACE-inhibitor (lisinopril) or calcium channel blocker (amlodipine) influence this response in subjects exposed to increased blood pressure vs increased retinal metabolism.

Inclusion Criteria:

• Type 1 diabetes
• 18-35 years of age
• Simplex retinopathy at last screening (Less than 10 retinal haemorrhages at the nearest ordinary screening examination)
• normotensive (BP not above 160 mmHg systolic or 100 mmHg diastolic)

Exclusion Criteria:

• Pregnancy
• Systolic Bloodpressure above 160 mmHg
• Diastolic bloodpressure above 100 mmHg
• Retinopathy grade higher than simplex retinopathy
• Prior retinal laser photocoagulation