Measuring Retinal Vessel Caliber in Relation to Dark Adaptation and Blood Glucose Level

Measuring Retinal Vessel Caliber in Relation to Dark Adaptation and Blood Glucose Level

The overall objective is to investigate, whether retinal blood vessel diameter change during the energy consuming dark adaptation process and if responses vary between low and high blood glucose.

All subjects are being studied using the same procedure. The study schedule takes place from 8 a.m. to 12 a.m. every time. Each subject shows up on one single day. Subjects are to show up fasting overnight with a break in insulin and/or oral antidiabetic treatment.

The study eye of each subject will be selected by randomisation. We seek to have an equal distribution of right and left eyes overall.

A first set of images will be taken after 5 minutes in "standardised daylight", in a room without light from outside, which eliminates any concerns about weather variations. After this the room is completely darkened. 2 set of images will be taken in the dark adapted state after 20 and 40 minutes. Subsequently the patient ingests the OGTT and will reach maximum blood glucose level after about 60-90 minutes. At this time, the subjects undergo the same "photo session" as above with high blood glucose levels.

Inclusion Criteria:

• Type 2 diabetic individuals.
• minimal or no diabetic retinopathy defined by no more than five microaneurysms or dot hemorrhages per eye on three non-stereoscopic 50 degree color fundus photographs

Exclusion Criteria:

• Test individuals with significant cataract, prior surgery to the eye, diabetic retinopathy, other serious eye disease, hypertension, other serious systemic disease