Measurement of Total Retinal Blood Flow and Oxygen Extraction in Patients With Diabetes and Healthy Subjects

The prevalence of diabetes and diabetes-associated complications is still increasing. Several major long-term complications of diabetes such as cardiovascular disease, chronic renal failure, diabetic retinopathy and others relate to the damage of blood vessels. Given that the eye provides the unique possibility in the human body to directly visualize blood vessels, much interest has been directed towards studying the ocular circulation and retinal oxygen metabolism.

Although data of large epidemiological studies indicate that changes in retinal vessel caliber reflect other diabetes related factors, such as fasting glucose levels, there is still conflicting evidence on blood flow alterations in patients with diabetes. Strongly related to ocular blood flow, investigation of retinal oxygen metabolism has received a lot attention. In particular, hypoxia is assumed to be major trigger of neovascularisation in the retinal of diabetic patients The present study seeks to investigate both ocular blood flow and tissue oxygen extraction in patients with type II diabetes. For this purpose, total retinal blood flow will be assessed with bi-directional Fourier Domain Doppler Optical Coherence Tomography (FDOCT). Furthermore, retinal oxygen saturation will be measured non-invasively by a fundus camera based system. Based on data of retinal blood flow and retinal oxygen saturation, retinal oxygen. This will help to better understand ocular blood flow changes and oxygen metabolism in patients with type II diabetes.


Eligibility Criteria:
Inclusion Criteria for healthy subjects:

* Men and women aged over 18 years
* Non-smokers
* Normal findings in the medical history unless the investigator considers an abnormality to be clinically irrelevant
* Normal ophthalmic findings, ametropy \< 6 Dpt.

Inclusion criteria for patients with diabetes

* Men and women aged over 18 years
* Non-smokers
* Previously diagnosed type II diabetes
* No, mild, moderate or severe non-proliferative diabetic retinopathy
* Normal ophthalmic findings except mild diabetic retinopathy, ametropy \< 6 Dpt.

Exclusion Criteria for healthy subjects:

* Symptoms of a clinically relevant illness in the 3 weeks before the first study day
* Presence or history of a severe medical condition as judged by the clinical investigator
* Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study (except oral contraceptive)
* untreated arterial hypertension (defined as either systolic blood pressure \>145 mmHg or diastolic blood pressure \>90 mmHg)
* Blood donation during the previous three weeks
* History or family history of epilepsy
* Presence of any abnormalities preventing reliable measurements in the study eye as judged by the investigator
* Best corrected visual acuity \< 0.8 Snellen
* Ametropy ≥ 6 Dpt
* Pregnancy, planned pregnancy or lactating

Exclusion Criteria for patients with diabetes:

* Participation in a clinical trial in the 3 weeks preceding the screening visit
* Symptoms of a clinically relevant illness in the 3 weeks before the first study day
* Presence or history of a severe medical condition, except diabetes, as judged by the clinical investigator
* untreated arterial hypertension (defined as either systolic blood pressure \>145 mmHg or diastolic blood pressure \>90 mmHg)
* Blood donation during the previous three weeks
* Moderate to severe non-proliferative or proliferative diabetic retinopathy
* Previous laser photocoagulation treatment
* History or family history of epilepsy
* Presence of any abnormalities preventing reliable measurements in the study eye as judged by the investigator
* Best corrected visual acuity \< 0.8 Snellen
* Ametropy ≥ 6 Dpt
* Pregnancy, planned pregnancy or lactating