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Background
Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. The existence of an effective autoregulation in the optic nerve circulation has been shown in animals and humans. The exact mechanism behind this autoregulation is still unknown. The motive for the investigation of optic nerve head (ONH) blood flow autoregulation is to enhance the understanding of pathologic eye conditions associated with ocular vascular disorders. To clarify the regulatory mechanisms of ONH microcirculation is of critical importance to understand the pathophysiology of glaucoma, because there is evidence that glaucoma is associated with optic nerve head ischemia. Several studies indicate that a disturbed autoregulation might contribute to glaucomatous optic neuropathy. Currently, five classes of intraocular pressure (IOP) reducing drugs are available for topical therapy in patients with glaucoma or elevated intraocular pressure. These drugs have also vasoactive properties, which may influence both the resting ocular circulation and the autoregulatory mechanisms of blood flow during changes in ocular perfusion pressure.
Study objective
To investigate the influence of common topical glaucoma therapy on ONH blood flow regulation during changes in IOP and systemic arterial blood pressure.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| 1 | Experimental |
| |
| 2 | Experimental |
| |
| 3 | Experimental |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Timolol (drug) | Drug | Timolol (0.5%, non-selective beta-blocker, Timoptic®, Merck Sharp & Dohme, Haarlem, Netherlands), dose 1 drop in one eye twice daily for two weeks |
|
| Measure | Description | Time Frame |
|---|---|---|
| Ocular perfusion pressure - ONH blood flow relationship | on 2 study days |
| Measure | Description | Time Frame |
|---|---|---|
| Composite measure: Blood pressure, heart rate | on 2 study days |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Gabriele Fuchsjaeger-Mayrl, MD | Department of Clinical Pharmacology | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Department of Clinical Pharmacology | Vienna | A-1090 | Austria |
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| dorzolamide (drug) | Drug | Dorzolamide (2%, carbonic anhydrase inhibitor, Trusopt®, Laboratoires Merck Sharp & Dohme - Chibret, France), dose: 1 drop in one eye twice daily for two weeks |
|
| brimonidine (drug) | Drug | Brimonidine (0.2%. alpha-2 adrenergic agonist, Alphagan®, Allergan Pharmaceuticals, Westport, Ireland), dose: 1 drop in one eye twice daily for two weeks |
|
| Laser Doppler flowmetry | Device | blood flow measurements at the temporal neuroretinal rim of the optic nerve head, in total 4x 9 minutes on 2 study days |
|
| Goldmann applanation tonometer | Device | intraocular pressure measurements, in total 2x 5 measurements on two study days |
|
| Suction cup method | Procedure | The IOP will be raised by an 11 mm diameter, standardized suction cup placed on the temporal sclera with the anterior edge at least 1 mm from the limbus; 4x 8 minutes on 2 study days |
|
| ID | Term |
|---|---|
| D005901 | Glaucoma |
| ID | Term |
|---|---|
| D009798 | Ocular Hypertension |
| D005128 | Eye Diseases |
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| ID | Term |
|---|---|
| D013999 | Timolol |
| D004364 | Pharmaceutical Preparations |
| C062765 | dorzolamide |
| D000068438 | Brimonidine Tartrate |
| D017078 | Laser-Doppler Flowmetry |
| ID | Term |
|---|---|
| D011412 | Propanolamines |
| D000605 | Amino Alcohols |
| D000438 | Alcohols |
| D009930 | Organic Chemicals |
| D020005 | Propanols |
| D000588 | Amines |
| D013830 | Thiadiazoles |
| D013844 | Thiazoles |
| D013457 | Sulfur Compounds |
| D001393 | Azoles |
| D006573 | Heterocyclic Compounds, 1-Ring |
| D006571 | Heterocyclic Compounds |
| D009025 | Morpholines |
| D010078 | Oxazines |
| D011810 | Quinoxalines |
| D006574 | Heterocyclic Compounds, 2-Ring |
| D000072471 | Heterocyclic Compounds, Fused-Ring |
| D003935 | Diagnostic Techniques, Cardiovascular |
| D019937 | Diagnostic Techniques and Procedures |
| D003933 | Diagnosis |
| D012212 | Rheology |
| D008919 | Investigative Techniques |
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