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

Study Overview
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Brief Summary
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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.

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

Conditions
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Retinal Blood Flow

Intervention / Treatment
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* Device: Fourier Domain Color Doppler Optical Coherence Tomography (FDOCT)


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 99 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: 30 patients with no signs of diabetic retinopathy<br> | Device: Fourier Domain Color Doppler Optical Coherence Tomography (FDOCT)<br>* Fourier domain OCT is based on a local phase analysis of the backscattered signal and allows for bidirectional Doppler flow imaging.(Leitgeb et al. 2003a; Leitgeb et al. 2003b) It does not need reference arm scanning and records one full depth and Doppler profile in parallel. The system operates with an equivalent A-scan rate of 25 kHz and allows real time imaging of the color encoded Doppler information together with the tissue morphology at a rate of 2-4 tomograms (40 x 512 pixel) per second. Despite the high detection speed we achieve a system sensitivity of 86dB using a beam power of 500μW at the cornea. The fundus camera allows simultaneous view for selection of the region of interest. We observe bi-directional blood flow and pulsatility of blood velocity in retinal vessels with a Doppler detection bandwidth of 12.5 kHz and a longitudinal velocity sensitivity in tissue of 200μm/s. Diffuse luminance flicker will be applied during the measurements for 60 seconds.<br>|
| Other: 30 patients with mild diabetic retinopathy<br> | Device: Fourier Domain Color Doppler Optical Coherence Tomography (FDOCT)<br>* Fourier domain OCT is based on a local phase analysis of the backscattered signal and allows for bidirectional Doppler flow imaging.(Leitgeb et al. 2003a; Leitgeb et al. 2003b) It does not need reference arm scanning and records one full depth and Doppler profile in parallel. The system operates with an equivalent A-scan rate of 25 kHz and allows real time imaging of the color encoded Doppler information together with the tissue morphology at a rate of 2-4 tomograms (40 x 512 pixel) per second. Despite the high detection speed we achieve a system sensitivity of 86dB using a beam power of 500μW at the cornea. The fundus camera allows simultaneous view for selection of the region of interest. We observe bi-directional blood flow and pulsatility of blood velocity in retinal vessels with a Doppler detection bandwidth of 12.5 kHz and a longitudinal velocity sensitivity in tissue of 200μm/s. Diffuse luminance flicker will be applied during the measurements for 60 seconds.<br>|
| Other: 30 patients with moderate to severe diabetic retinopathy<br> | Device: Fourier Domain Color Doppler Optical Coherence Tomography (FDOCT)<br>* Fourier domain OCT is based on a local phase analysis of the backscattered signal and allows for bidirectional Doppler flow imaging.(Leitgeb et al. 2003a; Leitgeb et al. 2003b) It does not need reference arm scanning and records one full depth and Doppler profile in parallel. The system operates with an equivalent A-scan rate of 25 kHz and allows real time imaging of the color encoded Doppler information together with the tissue morphology at a rate of 2-4 tomograms (40 x 512 pixel) per second. Despite the high detection speed we achieve a system sensitivity of 86dB using a beam power of 500μW at the cornea. The fundus camera allows simultaneous view for selection of the region of interest. We observe bi-directional blood flow and pulsatility of blood velocity in retinal vessels with a Doppler detection bandwidth of 12.5 kHz and a longitudinal velocity sensitivity in tissue of 200μm/s. Diffuse luminance flicker will be applied during the measurements for 60 seconds.<br>|
| Other: 30 healthy age-and sex- matched control subjects<br> | Device: Fourier Domain Color Doppler Optical Coherence Tomography (FDOCT)<br>* Fourier domain OCT is based on a local phase analysis of the backscattered signal and allows for bidirectional Doppler flow imaging.(Leitgeb et al. 2003a; Leitgeb et al. 2003b) It does not need reference arm scanning and records one full depth and Doppler profile in parallel. The system operates with an equivalent A-scan rate of 25 kHz and allows real time imaging of the color encoded Doppler information together with the tissue morphology at a rate of 2-4 tomograms (40 x 512 pixel) per second. Despite the high detection speed we achieve a system sensitivity of 86dB using a beam power of 500μW at the cornea. The fundus camera allows simultaneous view for selection of the region of interest. We observe bi-directional blood flow and pulsatility of blood velocity in retinal vessels with a Doppler detection bandwidth of 12.5 kHz and a longitudinal velocity sensitivity in tissue of 200μm/s. Diffuse luminance flicker will be applied during the measurements for 60 seconds.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Total retinal blood flow (DVA and FDOCT) | To determine the total blood flow in the eye, OCT measurements were performed with a rectangular scanning pattern around the optical nerve head. | 60 minutes |