Coupling of Neural Activity and Retinal Blood Flow in Diabetes

Terminated

Brief Summary: The prevalence of diabetes is increasing and the management of the disease is nowadays considered a major challenge. Affected patients have increased mortality and morbidity as well as a significant drop in the quality of life. The complications of diabetes can be classified as microvascular (e.g. nephropathy, neuropathy or retinopathy) or macrovascular (e.g. cardiovascular or cerebrovascular).

Several large-scale epidemiologic studies indicating that wider retinal venous caliber is strongly associated with the fasting glucose level as well as with diabetes. Another retinal vascular abnormality that is associated with diabetes is an abnormal retinal vascular response to flicker stimulation. Retinal vessel dilatation in response to stimulation with diffuse flicker light occurs due to a phenomenon called neurovascular coupling. This means that increased activity of neurons is associated with an increased retinal metabolism. This leads to a release of endogenous vasodilator substances and increased blood flow. However, previous studies were limited by the fact that retinal vessel diameters and blood flow were not measured simultaneously.

The present study aims to investigate whether the response of retinal vessel diameters and blood flow velocities to flicker stimulation is altered in patients with diabetes. Both parameters will be measured in real time using Fourier Domain Doppler OCT.

Recruitment & Eligibility

Inclusion Criteria

Men and women aged over 18 years, nonsmokers
Normal findings in the medical history (except diabetes) and physical examination unless the investigator considers an abnormality to be clinically irrelevant
normal laboratory findings (except diabetes associated parameters) unless the investigator considers the abnormality to be clinically irrelevant
normal ophthalmic findings (except mild diabetic retinopathy), Ametropia less than 6 diopters
inclusion criterion of patients is type I diabetes with non or mild non-proliferative retinopathy

Exclusion criteria

Any of the following will exclude a healthy subject from the study:

Regular use of vasoactive drugs
Abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study
Symptoms of a clinically relevant illness in the 3 weeks before the first study day
Blood donation during the previous 3 weeks
History or presence of any ocular pathology
History or family history of epilepsy
Systemic hypertension defined as systolic blood pressure >150mmHg, diastolic blood pressure >90mmHg
Pregnancy

Any of the following will exclude a subject with diabetes from the study:

Presence of non-insulin dependent diabetes, maturity onset diabetes of the young (MODY diabetes)
History or presence of any other diabetes induced vascular pathologies or any other ocular condition other then diabetic retinopathy
Best corrected visual acuity <0.8
Previous laser photocoagulation treatment
Systemic hypertension defined as systolic blood pressure >150mmHg, diastolic blood pressure >90mmHg
History or family history of epilepsy
Abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study
Symptoms of a clinically relevant illness in the 3 weeks before the first study day
Blood donation during the previous 3 weeks
Pregnancy

Primary Outcome Measures

Name	Time	Method
Retinal blood flow velocities	18 months
Retinal vessel diameters	18 months

Secondary Outcome Measures

Name	Time	Method