Are There Changes in the Nerve Fiber Layer (NFL) After Lowering of Eye Pressure?

Study Overview
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Brief Summary
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The aim of this study was to evaluate structural and functional improvement after lowering intraocular pressure (IOP) in patients with glaucoma using Spectral Domain Optical Coherence Tomography (SD-OCT), Visual Field (VF) testing, and Visual Evoked Potential (VEP).

Detailed Description
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Glaucoma exhibits characteristic changes to the optic nerve in the back of the eye. The optic nerve is formed when fibers that overlay the retina come together. This layer is called the retinal nerve fiber layer (RNFL). Optical Coherence Tomography (OCT) is a machine that scans eyes and has the capability of measuring thickness of various layers in the retina and RNFL. This provides important anatomical information. VEP (visual evoked potential) is an imaging system that measures electrical signals from the eye to the brain by using electrodes placed on the forehead and back of head. This is similar in principal to an electrocardiogram of the heart. Visual field testing is done to evaluate the extent of side vision loss caused by various diseases of the eye, including glaucoma. This testing is performed as you stare at a small light directly in front of your eye while lights flash one at a time in every direction on a screen surrounding the central light. You push a button each time you see a flash out of the corner of your eye. Lowering intraocular pressure (IOP) in the eye has been shown to result in reversal of glaucoma changes of the optic nerve in some patients. It has also been suggested that improvement in function (visual field) has been associated with improved optic nerve appearance. This study seeks to provide evidence for reversal of disc appearance and visual function following IOP lowering interventions.

Official Title
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Reversible Structural and Functional Changes After Intraocular Pressure Reduction in Patients With Glaucoma

Conditions
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Glaucoma

Intervention / Treatment
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* Diagnostic Test: Optical Coherence Tomography (OCT)
* Diagnostic Test: Visual evoked potential (VEP)
* Diagnostic Test: Humphrey Visual Field (HVF)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: All patients with glaucoma (primary open-angle glaucoma, angle recession glaucoma, exfoliation syndrome glaucoma, pigmentary glaucoma and chronic angle closure glaucoma) in whom a pressure-lowering intervention was conducted Exclusion Criteria: Inability to obtain reliable field or optical coherence tomography pre-intervention Visual acuity less than 20/40, Age <18 or >90 years, Other cause for visual field loss not glaucoma, that is, visual field loss due to cataract optic neuropathies, retinal disease Spherical equivalent refractive error > +5.00 Diopters and > 3.00 Diopters cylinder Concomitant cataract and glaucoma surgery

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 90 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| IOP between 22-32 mmHg<br>Forty four (44) patients with intraocular pressure between 22 and 32 millimeters (mmHg) of mercury will undergo Optical Coherence Tomography (OCT); Visual Evoked Potential (VEP); and Humphrey Visual Field (HVF). | Diagnostic Test: Optical Coherence Tomography (OCT)<br>* Optical Coherence Tomography (OCT) is a machine that scans eyes and has the capability of measuring thickness of various layers of the retina and nerve fiber layer (NFL).<br>* Other names: OCT;Diagnostic Test: Visual evoked potential (VEP)<br>* Visual Evoked Potential (VEP) is an imaging system that measures electrical activity from the eye to the brain by using electrodes placed on forehead and back of the head similar to electroencephalogram (EEG).<br>* Other names: VEP;Diagnostic Test: Humphrey Visual Field (HVF)<br>* Humphrey Visual Field (HVF) is a test done to evaluate how much peripheral (side) vision has been lost due to glaucoma.<br>* Other names: VF;|
| IOP greater than 32 mmHg<br>Six (6) patients with intraocular pressure greater than 32 millimeters of mercury (mmHg) will undergo Optical Coherence Tomography (OCT); Visual Evoked Potential (VEP); and Humphrey Visual Field (HVF). | Diagnostic Test: Optical Coherence Tomography (OCT)<br>* Optical Coherence Tomography (OCT) is a machine that scans eyes and has the capability of measuring thickness of various layers of the retina and nerve fiber layer (NFL).<br>* Other names: OCT;Diagnostic Test: Visual evoked potential (VEP)<br>* Visual Evoked Potential (VEP) is an imaging system that measures electrical activity from the eye to the brain by using electrodes placed on forehead and back of the head similar to electroencephalogram (EEG).<br>* Other names: VEP;Diagnostic Test: Humphrey Visual Field (HVF)<br>* Humphrey Visual Field (HVF) is a test done to evaluate how much peripheral (side) vision has been lost due to glaucoma.<br>* Other names: VF;|
| IOP less than 22 mmHg<br>Eleven (11) patients with stable intraocular pressure (less than 22 millimeters of mercury (mmHg)) on ophthalmic solutions (eye drops) will undergo Optical Coherence Tomography (OCT); Visual Evoked Potential (VEP); and Humphrey Visual Field (HVF). | Diagnostic Test: Optical Coherence Tomography (OCT)<br>* Optical Coherence Tomography (OCT) is a machine that scans eyes and has the capability of measuring thickness of various layers of the retina and nerve fiber layer (NFL).<br>* Other names: OCT;Diagnostic Test: Visual evoked potential (VEP)<br>* Visual Evoked Potential (VEP) is an imaging system that measures electrical activity from the eye to the brain by using electrodes placed on forehead and back of the head similar to electroencephalogram (EEG).<br>* Other names: VEP;Diagnostic Test: Humphrey Visual Field (HVF)<br>* Humphrey Visual Field (HVF) is a test done to evaluate how much peripheral (side) vision has been lost due to glaucoma.<br>* Other names: VF;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Visual Field Mean Deviation | Visual field mean deviation as measured in decibels (dB) is the amount of visual field loss compared to age matched controls (people with no eye diseases or visual field loss). Brightness of the flashes of light used to test peripheral vision during a visual field test is measured in decibels. Brighter light has lower number in decibels. The dimmer the light, the higher the number in decibels with a range of 0 to 40 dB. | 12 months | 
| Retinal Nerve Fiber Layer (RNFL) Thickness Measurement | Retinal nerve fiber layer (RNFL) thickness in different quadrants of optic nerve and macula are measured pre and postoperatively to evaluate structural changes. | 12 months | 
| Average Cup to Disc Ratio | Cup to disc ratio is used to evaluate structural changes comparing the size of the cup to the size of the disc during dilated ophthalmic examination. High eye pressure can cause the cup to enlarge, closer to the size of the disc. This measurement is used to follow progression in glaucoma. A normal range for cup to disc ratio would be 0.0 to 0.4. Advanced glaucoma would be 0.8 to 0.9 cup to disc ratio. | 12 months | 
| Visual Evoked Potential Amplitudes | VEP amplitudes at high contrast as measured in microvolts (μV). Electroencephalogram (EEG) measures electrical activity in the brain. VEP measures electrical activity in areas of the brain responsible for vision by using EEG electrodes. The amplitude measurement is the peak of the energy generated (strongest strength of the signal) from the eye's response to the visual stimulus during the VEP. | 12 months | 
| Visual Evoked Potential Latency | VEP latency at high contrast as measured in milliseconds (ms). Electroencephalogram (EEG) measures electrical activity in the brain. VEP measures electrical activity in areas of the brain responsible for vision by using EEG electrodes. VEP latencies measure the duration in time of the energy generated (duration of the signal) from the eye's response to a visual stimulus during the VEP. | 12 months | 
| Visual Field | Visual field pattern standard deviation in decibels (dB). Visual field results compare visual field loss to age matched controls (people with no eye diseases or visual field loss). Brightness of the flashes of light used to test peripheral vision during a visual field test is measured in decibels. With a localized defect in the visual field, pattern standard deviation (PSD) quantifies amount of loss and progression of glaucoma when in the beginning stages of the disease. | 12 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Visual Evoked Potentials, Optical Coherence Tomography, Visual Fields