Study on Ocular Blood Flow and the Orbital Cerebrospinal Fluid Pressure in Glaucoma

Study Overview
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Brief Summary
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Ocular blood flow has been consistently demonstrated to be altered in glaucoma patients when compared to otherwise healthy individuals. Numerous Doppler studies have shown a decrease in flow velocities in the retrobulbar arteries in what appears to be related to the degree of the glaucomatous disease. The anatomic pathway of the several arteries into the eye is intricately complicate, with at least one of them (the central retina artery) penetrating the optic nerve before entering the eye and supplying the innermost structures of the globe. As the optic nerve is surrounded by a layer of cerebrospinal fluid (CSF) which is in continuity with the rest of the central nervous system, this central retinal artery has also to cross this CSF containing compartment. Because of the intrinsic pressure this CSF - corresponding to the intracranial pressure at the orbital level - the possibility exists that this pressure around the optic disc could affect the blood flow of the arteries that go through it. The investigators will try to detect if a correlation exists between the optic nerve sheath diameter and the blood flow in the retrobulbar vessels of glaucoma patients.

Detailed Description
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Visual field testing will be performed. Structural analysis of the retinal nerve fiber layer (through confocal microscopy)will be performed. Color Doppler Imaging of the retrobulbar vessels will be performed. Peak and end diastolic velocities, resistivity index will be calculated from the Doppler waveform. B-scan ultrasound of the optic nerve sheath diameter will be performed. the measure will take place at 3mm behind the globe.

Official Title
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Correlation Between Ocular Blood Flow and the Optic Nerve Sheath Diameter in Patients With Primary Open-angle Glaucoma

Conditions
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Open Angle Glaucoma, Normal Tension Glaucoma

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: individuals over 18 years old willing to sign an informed consent and able to comply with the requirements of the study having no other ocular diseases besides glaucoma Exclusion Criteria: history of ocular trauma intraocular surgery (except for cataract surgery) eye disease (except glaucoma) systemic diseases with ocular involvement like diabetes

Ages Eligible for Study
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Minimum Age: 18 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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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Controls<br>Healthy volunteers with no family history of glaucoma, an increased or asymmetrical cup/disc ratio or any other optic disc structural change (notching, disc hemorrhage) or an intraocular pressure (IOP) above 21 mmHg that could suggest possible glaucoma suspects. | |
| Primary open-angle glaucoma<br>Patients with a characteristic optic disc damage (based on cup/disc ratio, thinning of neuroretinal rim, notching, disk hemorrhages, etc.) and visual field defects, with at least one measurement of IOP of >21 mmHg required | |
| Normal Tension Glaucoma<br>Patients with a characteristic optic disc damage (based on cup/disc ratio, thinning of neuroretinal rim, notching, disk hemorrhages, etc.) and visual field defects, with at maximum recorded IOP of < 21 mmHg | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Flow velocity of retrobulbar vessels |  | Participants will be followed for the duration of hospital stay, an expected average of 2 hours |