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Retinal Blood Flow clinical trials

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NCT ID: NCT04596826 Recruiting - Retinal Blood Flow Clinical Trials

The Effect of Dronabinol on Ocular Hemodynamics in Patients With Primary Open Angle Glaucoma

Start date: November 11, 2020
Phase: Phase 2
Study type: Interventional

Glaucoma is among the leading causes for irreversible blindness worldwide. While lowering intraocular pressure (IOP) remains the mainstay of therapy, there are still some patients who progress despite well-controlled IOP. There is evidence from several studies that ocular blood flow and its regulation is impaired in patients with glaucoma. Tetrahydrocannabinol (THC) has been used in the treatment for glaucoma in some countries for several years due to its IOP lowering effect. In addition, there is also evidence that THC features neuroprotective effects and improves ocular hemodynamics. Dronabinol is a synthetic THC that is legally available in several European countries. It has the advantage that exact dosing of THC is possible in contrast to previously applied administration forms such as smoking. Due to its legal status in the past, data about the effect of THC on ocular blood flow and its regulation are sparse. In a recent study conducted in the investigators laboratory they found that single administration of dronabinol leads to a significant increase in optic nerve head (ONH) blood flow without impairing its autoregulatory capacity.The aim of the present study therefore is to investigate whether single administration of dronabinol alters optic nerve head (ONH) blood flow in patients with open angle glaucoma. In addition, other parameters for ocular blood flow will be measured, in particular retinal blood flow, retinal oxygen saturation and retinal neurovascular coupling. The study will be conducted in a parallel-group, randomized, double-masked, placebo-controlled, cross-over design. Patients will be randomized to either receive 5mg or 10mg dronabinol on one study day. Other studies investigating retinal hemodynamics or IOP after administration of THC also have used similar or slightly higher doses.

NCT ID: NCT03907163 Completed - Retinal Blood Flow Clinical Trials

The Effect of Tetrahydrocannabinol on Ocular Hemodynamics in Healthy Subjects

Start date: July 2, 2018
Phase: N/A
Study type: Interventional

Glaucoma is among the leading causes for irreversible blindness worldwide. While lowering intraocular pressure (IOP) remains the mainstay of therapy, there are still some patients who progress despite wellcontrolled IOP. There is evidence from several studies that ocular blood flow and its regulation is impaired in patients with glaucoma. Tetrahydrocannabinol (THC) has been used in the treatment for glaucoma in some countries for several years due to its IOP lowering effect. In addition, there is also evidence that THC features neuroprotective effects and improves ocular hemodynamics. Dronabinol is a synthetic THC that is legally available in several European countries. It has the advantage that exact dosing of THC is possible in contrast to previously applied administration forms such as smoking. Due to its legal status in the past, data about the effect of THC on ocular blood flow and its regulation are sparse. This holds true for basic research in healthy subjects as well as in patients with glaucoma.The aim of the present study therefore is to investigate whether single administration of THC alters optic nerve head (ONH) blood flow in healthy subjects. In addition, other parameters for ocular blood flow will be measured, in particular retinal blood flow, retinal oxygen saturation and retinal neurovascular coupling. The study will be conducted in a randomized, double-masked, placebocontrolled, two-way cross-over design. Subjects will receive 5mg dronabinol on one study day. This dose is the recommended starting dose for some indications in clinical practice. Other studies investigating retinal hemodynamics or IOP after administration of THC also have used similar or slightly higher doses.

NCT ID: NCT03552562 Recruiting - Retinal Blood Flow Clinical Trials

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

Start date: November 21, 2018
Phase: N/A
Study type: Interventional

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.

NCT ID: NCT01746615 Recruiting - Clinical trials for Branch Retinal Vein Occlusion

Assessment of Retinal Vessel Diameters and Red Blood Velocities in Patients With BRVO and Healthy Subjects

Start date: August 2015
Phase: N/A
Study type: Interventional

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.

NCT ID: NCT01692821 Completed - Retinal Blood Flow Clinical Trials

Effect of Systemic Hypoxia and Hyperoxia on Retinal Oxygen Saturation

Start date: June 2012
Phase: Phase 4
Study type: Interventional

Adequate perfusion and oxygenation is essential for the function of the inner retina. Although it is known that oxygen tension is very well autoregulated in the retina, the physiological mechanisms behind this regulation process are not fully explored. The development of new instruments for the non-invasive measurement of oxygen tension in retinal vessels now allows for the more precise investigation of these physiological processes. The current study seeks to evaluate the retinal oxygen saturation in healthy subjects while breathing different oxygen mixtures to achieve a hypoxic and a hyperoxic state.