Assessment of retinal vessel calibers combined with bidirectional Fourier domain optical coherence tomography (FDOCT) for measurement of retinal blood velocities is a new and sophisticated method for assessing retinal blood flow in humans. The valid measurement of retinal blood flow is of significant importance, because it is known that major ophthalmic diseases are associated with alterations in blood flow.

As such, retinal vascular occlusive diseases represent a major cause of visual impairment and blindness. The prevalence of the disease is between 0.7 and 1.6%. Compression of the retinal veins at arterio-venous (AV) crossings plays an important role in the development of branch retinal vein occlusion (BRVO). The mechanical narrowing of the vessel lumen is supposed to be the mechanism behind this fact. The present study should elucidate how BRVO influences retinal blood flow at retinal vessel crossings in comparison to healthy control subjects. Retinal blood flow at retinal bifurcations will also be assessed. In addition, a fundus image will be taken to assess retinal oxygen saturation.

For the first time we use a combination of a dynamic vessel analyzer (DVA) with bidirectional Fourier domain optical coherence tomography (FDOCT) to assess retinal blood flow. Whereas the DVA provides information concerning retinal vessel caliber, FDOCT provides laser Doppler information in addition to conventional optical coherence tomography, allowing the observation of blood flow dynamics simultaneously.

In the present study we hypothesize that the DVA in combination with FDOCT is a suitable new tool for the assessment of blood flow in healthy subjects and in patients with BRVO.

Inclusion Criteria:

Inclusion criteria for healthy subjects

• Men and women aged over 18 yrs
• Nonsmokers
• Normal findings in the medical history unless the investigator considers an abnormality to be clinically irrelevant
• Normal ophthalmic findings, ametropia < 6 Dpt.

Inclusion criteria for patients with BRVO

• Age ≥ 18a
• Patients with branch retinal vein occlusion with a history of 3 to 9 months in one eye
• No history of BRVO in the fellow eye
• Temporal inferior or superior vein occlusion
• Ametropia < 6 Dpt

Exclusion Criteria:

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

• Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study (except oral contraceptive)
• Symptoms of a clinically relevant illness in the 3 weeks before the first study day
• Blood donation during the previous 3 weeks
• Pregnancy
• Any abnormalities preventing reliable measurements as judged by the investigator

Any of the following will exclude a patient with BRVO from the study:

• Presence of intraocular pathology other than branch retinal vein occlusion
• Blood donation during the previous 3 weeks
• Clinical trial in the 3 week preceding the study
• Pregnancy
• Any abnormalities preventing reliable measurements as judged by the investigator