Non-invasive Measurement of Retinal Blood Flow Based on Vessel Analysis and Fourier Domain Optical Coherence Tomography in Patients With Hypertensive Retinopathy

Non-invasive Measurement of Retinal Blood Flow Based on Vessel Analysis and Fourier Domain Optical Coherence Tomography in Patients With Hypertensive Retinopathy

Recently, a new and sophisticated method for assessment of retinal blood flow and retinal blood flow velocity profiles has become available. This technique is based on the combination of measurement of retinal vessel calibers with bidirectional Fourier domain optical coherence tomography (FDOCT). The valid measurement of retinal blood flow is of significant importance, because it is known that major ophthalmic diseases, such as hypertensive retinopathy, are associated with alterations in blood flow.

Hypertensive retinopathy is the most common manifestation of arterial hypertension in the eye. Elevated systemic blood pressure leads to generalized arteriolar narrowing caused by vasospasms and increased vascular tone. Further in the disease process, focal arteriolar narrowing, retinal haemorrhages, hard exudates and cotton wool spots can occur. Previous studies have shown that blood flow in the extraocular vessels and in the choroid is compromised in patients with arterial hypertension. However, data on the impact of arterial hypertension on retinal blood flow and retinal blood flow velocities are lacking.

The present study sets out to compare total retinal blood flow and retinal velocity profiles in patients with hypertensive retinopathy and healthy age- and sex-matched controls. Ocular perfusion pressure will be calculated based on measurements of blood pressure and intraocular pressure to allow for calculation of vascular resistance. In addition, velocity profiles at arterio-venous crossings will be measured. It is hypothesized that these velocity profiles are considerably modified in patients with stage 2 and 3 hypertensive retinopathy compared to healthy controls because of pronounced arterio-venous compression.

Inclusion 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
• Systolic Blood Pressure ≤ 120 mmHg and Diastolic Blood Pressure ≤ 80 mmHg
• Normal ophthalmic findings, ametropia < 6 Dpt.

Inclusion criteria for patients with hypertensive retinopathy

• Men and women aged over 18 years
• Hypertensive retinopathy stage 2 or 3
• Normal ophthalmic findings except hypertensive retinopathy stage 2 and 3, ametropia < 6 Dpt.

Exclusion Criteria:

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

• 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
• Presence or history of arterial hypertension
• Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study (except oral contraceptive)
• Blood donation during the previous three weeks
• Presence of any abnormalities preventing reliable measurements in the study eye as judged by the investigator
• Ametropia >= 6 Dpt
• Pregnancy, planned pregnancy or lactating

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

• 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 as judged by the clinical investigator
• Blood donation during the previous three weeks
• Hypertensive retinopathy stage 4
• Presence of any abnormalities preventing reliable measurements in the study eye as judged by the investigator
• Ametropia >= 6 Dpt
• Pregnancy, planned pregnancy or lactating